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THE  LIBRARY 

OF 

THE  UNIVERSITY 
OF  CALIFORNIA 

PRESENTED  BY 

PROF.  CHARLES  A.  KOFOID  AND 
MRS.  PRUDENCE  W.  KOFOID 


THE 


DISSECTOR'S  MANUAL 


OF 


PRACTICAL    ANB    SURGICAL 


ANATOMY. 

ly 


BY 

ERAS  MTTS^WTL  S  0  N.  F.  R.  S. 

AUTHOR  OF  "A  SYSTEM  OP  HUMAN  ANATOMY,"  ETC. 

THE  THIRD  AMERICAN 
FROM  THE  LAST  REVISED  LONDON  EDITION. 


tottfj  ©tu 


anfc  jFiftj-four 


EDITED   BY 

WILLIAM  HUNT,  M.D. 

PEMO.NttTRATOR  OF  ANATOMY  IN  THE  UNIVERSITY  OF  PENNSYLVANIA. 


PHILADELPHIA: 

BLANCHARD    AND    LEA. 
1856. 


Entered  according  to  the  Act  of  Congress,  in  the  year  1856,  by 
BLANCHARD    AND     LEA, 

in  the  Office  of  the  Clerk  of  the  District  Court  of  the  United  States  in  and 
for  the  Eastern  District  of  Pennsylvania. 


PHILADELPHIA : 
T.  K.  AND  P.  G.  COLLINS,  PRINTERS. 


TO 


JONES  QUAIN,  M.  D., 


THIS 


THE    AUTHOR'S    FIRST    WORK 


IN  EVER  GRATEFUL  REMEMBRANCE. 


PREFACE 

BY  THE  AMERICAN  EDITOR. 


THE  first  two  American  editions  of  Mr.  Wilson's  book 
were  published  under  the  supervision  of  Dr.  Goddard,  who 
altered  the  arrangement  of  the  English  work,  so  as  to 
agree  with  the  mode  of  dissection  usually  adopted  in  Ame- 
rica. "In  the  English  school"  (as  Dr.  Goddard  observes), 
"  the  dissector  generally  commences  with  the  extremities, 
while  with  us  the  muscles  and  viscera  of  the  abdomen 
claim  the  student's  first  attention ;"  hence  it  was  thought 
best  to  arrange  the  work  accordingly. 

The  present  edition — besides  being  much  enlarged — is 
somewhat  modified  from  the  others.  New  cuts  have  been 
added,  illustrating  many  important  subjects,  and  the  editor 
can  only  hope  that  this  guide  to  a  knowledge  of  Practical 
Anatomy  will  fully  sustain  the  reputation  of  its  predeces- 
sors. The  additions  are  inclosed  between  brackets  [  ]. 

PHILADELPHIA,  May,  1856. 

1* 


CONTENTS. 


CHAPTER  I. 

PAOR 

DISSECTION    .            .  .         .  .         .            .  .  .  vKi  , ,  A)  26 

CHAPTER  II. 

ABDOtfBX. 

Superficial  anatomy              .            .        ^i^.  -,  *<?-.  v  •  31 

Muscles  of  the  abdomen      .             .            .  .•  .  .,  .  32 

Vessels  and  nerves  of  the  parietes              .  .  ......  .  39 

Spermatic  cord         .            .            ...  ,  ,.  .-,  %»jy  •  44 

Anatomy  of  hernia               .            .         ;  <i . ,  ^.,  .  .  45 

Cavity  of  the  abdomen        .            .        .,_•  ,f  J;  k  ,  4 ,  4  .  52 

Regions  and  position  of  viscera       .            .  ,,  ;  .  .  52 

Peritoneum  .            ...         - -.4.       i)r»%;- .  ,»,:.  .    *  /v  •  54 

Stomach       .  .         .            .   .        ^J;.       .^,  .  ;  ..fc^  .4    (  .  59 

Intestines     .  .         .            .            •            .  .  .^  .  60 

Vessels  and  nerves  of  the  alimentary  canal  .    i»    j  :  ?.<•  .  .  68 

Liver            .            .  .  J    ,  W:  -:  77 

Gall-bladder             .            .            .            .   .  *,,  ,  _» "•  ...  .  87 

Pancreas       .            .            .            .   .         .  •_  ',  • .  .  89 

Spleen           .....  .^  ,.:  ,  .  90 

Supra-renal  capsules            .            .            .  •.  \  •.-.'•  •  91 

Kidneys        .            ...            .            .  .  7  ».    ;  .  93 

Deep  vessels  and  nerves  of  the  abdomen    .  .  '    •»  j  .  96 

Abdominal  aorta      .             .            .            .  .  •  .  .  96 

Common  and  external  iliac  arteries             .  .  .  .99 

Inferior  vena  cava   .            .            .            .  .  ...  100 

Sympathetic  nerve  and  plexuses     .....  102 

Lymphatic  vessels  and  glands       •-.-.       pq  .  .  .  104 

Receptaculum  chyli             ......  105 

Deep  muscles  of  the  abdomen         •         "  ,~~"  .  .  •  105 

Diaphragm   .             •  .          .  .          .  .          •  .  ;  k  r  »'  <  .  105 

Lumbar  nerves  and  plexus    '           .            .   .  .  .^    .  •  J09 


Vlll  CONTENTS. 

CHAPTER  III. 

HEAD  AND  NECK. 

PAGE 

Muscles  of  the  head  and  face  .....       113 

Vessels  and  nerves  of  the  cranium  .  .  .  .116 

Parotid  gland  .  .  V'  ....       122 

Vessels  and  nerves  of  the  face        .....       125 

Facial  nerve  .  .  .  .  .  .  .125 

Facial  artery  .......       127 

Anatomy  of  the  orbit  .  .  .  .  .  .128 

Muscles  of  the  neck  ......       140 

Thyroid  gland  .  .  .  .  .  .  .       146 

Tracheotomy  and  laryngotomy        .....       147 

Submaxillary  gland  ......       148 

Sublingual  gland      .......       149 

Vessels  and  nerves  of  the  neck       .  .  .  .  .152 

External  jugular  vein  ;  operation    .  .  .  .  .153 

Posterior  triangular  space    .  .  .  .  .  .       154 

Cervical  nerves         .  .  .  .  .  .         •*  4       154 

Brachial  plexus  of  nerves    .  .  .  .  .  .156 

Subclavian  artery  and  branches      .  .  .  .  .157 

Operation  on  the  subclavian  artery  .  .  .  .158 

Common  carotid  artery         .  .  .  .  .  .161 

Operations  on  the  common  carotid  artery   .  .  .  .163 

Operation  on  the  arteria  innominata  .    •         .  .  .163 

Thoracic  duct  .   •         .  .  .  .  .  .       166. 

External  carotid  artery  and  branches      ">;yn          .  .  .166 

Fifth  pair  of  nerves  .  .  .  .  .  .176 

Internal  carotid  artery         .  .  .  .    -          .  .185 

Facial  nerve ;  deep  portion  .  .  ...  .       187 

Eighth  pair  of  nerves  .  .  .    .          .  .  .       189 

Hypoglossal  nerve    .  .  .  .  .  .  .193 

Sympathetic  nerve  .  .  .  .  ...  .193 

Prse vertebral  region  .         i-* &•-.''        .  .          H;K  .       196 

Pharynx       .  ,'  .         .  ,  ,   .          .   ,      -rv  .       198 

Soft  palate    .  .  .  .        ••%  V-          .  .  .       201 

(Esophagus  ,  .  .  .  .   .         .   ,         .  .       203 

CHAPTER  IV. 

BRAIN  AND  SPINAL  CORD. 

Membranes  of  the  brain       .  .  .  .  .  .       £04 

Vessels  of  the  brain  .  209 


CONTENTS.  ix 

PAGE 

Cerebrum     .            .            .*"         .         '*  I            .  .  .  212 

Cerebellum  .             .            +  „         .             fj           .  .  .  .•  224 

Base  of  the  brain     .             •         .    .            .             .  .  .  226 

Medulla  obi ongata    .             .  •           «•           »•*"         »r      v  •    -  .  230 

Fibres  of  the  brain  .             #•           ..           .             ..  ."  '. .  233 

Cranial  nerves          ..          .  •           .             ..  '••-'•  »•:  .  235 

Sinuses  of  the  cranium        »»           .             .-           ..  .  .  242 

Spinal  cord    .             ..         ?v-:       ;  V        •  C           :*  .  246 


CHAPTER  V. 

ORGANS  OF  SENSE. 

Nose  and  nasal  fossae           .  .  .  .  •  *  252 

Appendages  of  the  eye         .  .  .  *  ,^.  ,.  .  .  258 

Lachrymal  apparatus           .  .  .  .,  (    *    .  .  261 

Eyeball         .            .            ..  .  ,v>t  .  .  ,    .„.  .  262 

Ear   .            .            ..           .  .  ...  -  .,'.»,  ,  .  271 

Mouth  and  tongue    .            .  .  .  .  ,•.«,,-  .  284 

Larynx          .             ..           .  .  .^:  .  .  ^.i(  .  288 

Skin              .  .          .            .  .  .  ".^  A  .  .297 

Appendages  of  the  skin       .  .  .  .  .  .  301 

CHAPTER  VI. 

THORAX. 

Boundaries  of  the  thorax     .  .  .  .  •  fc        .  •  305 

Pleurae ;  mediastinum          .  .  .  r.v>  .  .  306 

Phrenic  nerves          .             .  .  ;  .   i  -.  ,  .  307 

Lungs            .             .             .  .  •,-•:.  .•  •:•-.  •  308 

Heart            ./        .            .  .  .  ',  .  .  313 

Great  vessels  of  the  heart  .  .  .  .  «  .  .  324 

Nerves  of  the  thorax           .  .  .  .  ^  A  •  328 

Pneumogastric  nerve            .  .  .  f  ?  '••.,-,  •  328 

Sympathetic  nerve  .             .  .  .  .  ^  .  329 

Intercostal  nerves    .            .  .  .,*'•.  -,  .  331 

Trachea        .             .             .  .  *   y^  .  .    .  .  332 

(Esophagus  .             .             .  .  .  -^  «  ^  .  333 

Thoracic  aorta          .  m          .  .  •    .  . .  ..  ,  ^.  .  334 

Azygos  veins              .             .  .  •  ,  f  .  335 

Thoracic  duct            ,            .  336 


X  CONTENTS. 

CHAPTER  VII. 

UPPER  EXTREMITY. 

PAGE 

General  anatomy      .            •« .           .             .             .  ,•.#:•.>:  .  338 

Table  of  muscles      .             .             .             .             .  r -« »  ' ,'»  339 

Anterior  thoracic  region       .  .           .             .             .  .  »  343 

Mammary  gland       .             .             .             .           •  «  .  .  344 

Operations  on  the  axillary  artery ;  upper  part         .  .  .  347 

Anatomy  of  the  axilla          ......  348 

Operations  on  the  axillary  artery ;  lower  part          .  .  .  350 

Brachial  plexus  of  nerves   ......  352 

Anatomy  of  the  walls  of  the  thorax            .             .*  •  .  355 

Anatomy  of  the  shoulder  and  scapula         .             .  .  .  357 

Anterior  brachial  region       ....  V  'r^.  362 

Veins  of  the  bend  of  the  elbow       .             .             .  •  i    a  ,  362 

Accidents  from  venesection              .             .             .  '•'*'*  .  364 

Operations  on  the  brachial  artery    .             .             .  .  .  369 

Anatomy  of  the  forearm      .             .             .             .  .  .  371 

Operations  on  the  radial  artery        .             .             .  "    »  .  376 

Operations  on  the  ulnar  artery  £  379 

Palm  of  the  hand    .......  386 

CHAPTER  VIII. 

LOWER  EXTREMITY. 

Surgical  observations           ......  392 

Anterior  femoral  region        .             .             .             .  .  .  395 

Internal  femoral  region         ....  '"•«.'.  .  402 

Vessels  of  the  thigh             .             .             .             .  .  .  404 

Operations  on  the  femoral  artery     .             .             .  .  '  .*  405 

Nerves  of  the  thigh              .  •           .             .             .  .  .410 

Femoral  hernia        ..  •           .             .             .        * ':.'  ':"  ;  412 

Gluteal  region           ,*           .             .                          ."-^  ';"-."  •'••  .  416 

Posterior  femoral  regien       .-           .             .             ,t>"  ™ '."  .  423 

Popliteal  region        .  •          .             .             .             .  •'"-  Y  '  .  425 

Operation  on  the  popliteal  artery    .             .             .  VY  ;  .  426 

Anatomy  of  the  leg               ...  -           .             .  .  ^  428 

Anterior  tibial  region            .  •           .  •           .             .  .  .  430 

Operations  on  the  anterior  tibial  artery       .             .  •  .  .  433 

Dorsal  region  of  the  foot      .  '          .  *          .  -          .  .  .  434 

Operation  on  the  dorsalis  pedis  artery        .             .  •  .  435 

Fibular  region          .            •           .•        •    •.            .  .  .  436 


CONTENTS.  Xl 

PAQB 

Posterior  tibial  region          »;:       *•"'      'V          •.            •            •  437 

Operations  on  the  posterior  tibial  artery      .             »             .             .  442 

Operations  on  the  peroneal  artery  .              .            .            .             .  443 

Sole  of  the  foot         .    .        .   *        .    .        *?;;        .:!          •"-<      '  i'  445 

Actions  of  muscles  of  the  lower  extremity              v  .      v."    '    »:  451 

CHAPTER  IX. 

PELVIS  AND  ORGANS  OF  GENERATION. 

Viscera  of  the  pelvis            .            .            .        '''1''    '**-**<      '".7  452 

Pelvic  fascia             .......  454 

Muscles  of  the  cavity  of  the  pelvU         i.'. U.'         .            .            .  455 
Rectum        .            .            .        ^...^         .            .            .            .456 

Urinary  bladder       .  ...  .  .  .  .456 

Prostate  gland          .            .            .                         .          '  . '           .  460 

Vesiculee  seminales              .             .             .            '"»'"•••'           .  460 

Vessels  of  the  pelvis            .             .           ;'i             ,  -'       ••/           .  461 

Nerves  of  the  pelvis             .             .         .  -.         '  :  ;    •        .             .  465 

Male  organs  of  generation   ......  468 

Penis             .             .             .             .             .             ....  468 

Urethra        ........  470 

Testes           ........  472 

Female  pelvis           .......  476 

Female  organs  of  generation            .....  478 

Uterus          ........  478 

External  organs        .             .             .             .             .             .             .  483 

CHAPTER  X. 

REGION  OP  THE  BACK. 

Table  of  muscles      .......  485 

Cutaneous  nerves  of  the  back          .....  486 

Nerves  and  vessels  of  the  back       .             .             .             .             •  493 

Table  of  origins  and  insertions  of  muscle*              .             .             .  500 

CHAPTER  XL 

ANATOMY  OF  THE  PERINEUM. 

General  considerations         ......  503 

Internal  pudic  artery            ......  511 

Operation  of  lithotomy        '.  »  .  •  .  .616 

Female  perineum     .            .            .            .            .            •            •  517 


Xii  CONTENTS. 

• 

CHAPTER  XII. 

ANATOMY  OF  THE  FOSTUS. 

PAGE 

Exterior  anatomy  of  the  foetus         .  .  .  .  '.519 

Foetal  circulation     .  .  .  .  .  519 

Foetal  thymus  gland  ...  .  .  .  .523 

Foetal  heart  .  .        ,   ,fj!r     ,  r^  .  .  .       526 

Viscera  of  the  abdomen      .  .  .  .  .  .526 

Viscera  of  the  pelvis  ......       528 

Foetal  testes,  their  descent  ......      528 

CHAPTER  XIII. 

LIGAMENTS. 

General  anatomy      .  .  .  ....  .530 

Ligaments  of  the  trunk       .  .  .  .         .?-,.«. u.  •       533 

Ligaments  of  the  upper  extremity  .  .  .  .       545 

Ligaments  of  the  lower  extremity  .  .  .  »;  •      555 


THE 


DISSECTOH. 


CHAPTER  I. 

DISSECTION. 

THE  human  body  is  composed  of  certain  principal  structures, 
which  occupy  the  same  relative  position  to  each  other,  where- 
soever they  be  examined.  To  obtain  a  good  knowledge  of  these, 
is  the  first  duty  of  the  dissector ;  the  more  particularly,  that  a 
just  conception  of  their  nature  and  position  will  greatly  facilitate 
the  future  progress  of  his  studies.  These  parts  may  be  thus 
arranged,  in  the  order  of  their  superposition: — 

Integument. 

Superficial  fascia. 

Deep  fascia. 

Muscles. 

(  Arteries. 

Vessels,  •<  Veins. 

(  Lymphatics. 

Nerves. 

Bones  and  ligaments, 

and  cellular  tissue,  the  common  connecting  medium  of  the  body, 
by  which  they  are  all  held  together. 

The  business  of  dissection,  therefore,  consists  in  dividing  and 
turning  aside  the  integument,  the  superficial  fascia,  and  the  deep 
fascia;  in  freeing  the  muscles  from  their  enveloping  cellular 
tissue ;  in  separating  them,  so  as  to  display  the  vessels  and  nerves 
which  lie  between  them ;  and  in  following  the  latter  to  their  ulti- 
mate ramifications. 

In  the  same  manner  the  performance  of  an  operation  with  the 
aid  of  the  knife,  as,  for  example,  the  tying  of  an  artery,  requires 
the  division  of  the  integument,  superficial  fascia,  and  deep  fascia, 
the  separation  of  the  muscles,  and  the  finding  and  securing  of  the 
vessel.  So,  again,  in  amputation,  the  same  structures  are  to  be 
3 


26  THE   DISSECTOR. 

divided,  and  in  precisely  the  same  order.  Thus  the  student  will 
perceive  that  one  principal  object  of  dissection  is  the  practice  of 
his  knife  in.  the  division  and  separation  of  these  parts,  so  as  to 
enable  him  to  accomplish  his  end  with  ease  and  dexterity.  All 
the  operations  of  dissection  should  be  conducted  with  the  same 
delicacy  that  is  observed  in  the  treatment  of  the  living  subject. 
The  result  of  such  practice  must  be  obvious — the  attainment  of 
that  confidence  and  precision  in  surgical  manipulations,  which  are 
so  necessary  to  the  successful  surgeon. 

Now,  let  us  inquire  into  the  nature  of  the  structures  composing 
the  preceding  table. 

The  INTEGUMENT  (integere,  to  cover  in)  is  the  investing  cover- 
ing of  the  entire  body ;  in  common  parlance,  the  skin :  it  consists 
of  the  epiderma  and  derma. 

The  Epiderma  (cuticle,  scarfskin)  is  the  thin,  horny  layer 
which  forms  the  surface  of  the  integument.  It  is  produced  by 
the  derma,  upon  which  it  is  exactly  moulded;  is  dense  and  hard 
on  the  outer  surface,  but  softer  within ;  hence  it  has  been  described 
as  consisting  of  two  layers,  of  which  the  inner  and  deeper  layer 
is  called  rete  mucosum  (rete,  because  the  depressions  caused  by 
the  papillae  of  the  derma  give  it  the  appearance  of  a  net;  mucosum, 
from  its  softness).  In  intimate  structure,  the  epiderma  is  com- 
posed of  nucleated  cells,  which  are  thick  in  the  part  called  rete 
mucosum,  but  flattened  into  thin  scales  in  the  outer  layer.  These 
cells  are  the  seat  of  the  pigment  of  the  skin;  which  has  a  deeper 
hue  in  the  thick  and  newly-formed  cells  than  in  the  scales  of  the 
horny  layer,  where  it  is  pale  and  almost  lost,  from  drying.  The 
epiderma  is  very  thick  in  the  palms  of  the  hands  and  soles  of  the 
feet,  and,  in  a  state  of  increased  density,  constitutes  the  nails. 

The  Derma,  or  cutis,  or  true  skin,  also  presents  a  superficial 
and  a  deep  layer.  The  former,  constituting  the  surface  of  the 
derma,  and  formed  into  numberless  minute  papilla,  is  termed 
the  papillary  layer.  The  latter,  being  the  chief  bulk  of  the 
derma,  is  the  corium.  The  papillary  layer  contains  the  capilla- 
ries and  ultimate  nervous  plexuses  of  the  skin;  the  corium  is 
composed  of  fibres  and  strands  of  fibrous  tissue,  which  form 
meshes  of  extreme  fineness  in  the  superficial  portion  of  the  layer, 
and  coarser  meshes  in  its  deeper  part.  The  meshes  of  the  corium 
are  occupied  by  fat,  and  give  passage  to  the  vessels  and  nerves 
of  the  papillary  layer. 

The  SUPERFICIAL  FASCIA  (fascia,  a  bandage),  placed  immediately 
beneath  the  tegument  over  every  part  of  the  body,  is  the  medium 
of  connection  between  that  layer  and  the  deeper  parts.  It  con- 
sists of  fibro-cellular  tissue,  in  which  is  deposited  an  abundance 
of  adipose  tissue.  The  fat  being  a  bad  conductor  of  caloric, 
serves  to  retain  the  warmth  of  the  body ;  while  it  forms  at  the 


DEEP   FASCIA — MUSCLES  —  VESSELS.  2t 

same  time  a  yielding  medium,  through  which  the  minute  vessels 
and  nerves  pass  to  the  papillary  layer  of  the  skin,  without  incur- 
ring the  risk  of  obstruction  from  injury  or  pressure.  By  dissec- 
tion, the  superficial  fascia  may  be  separated  into  two  layers, 
between  which  are  found  the  superficial  or  cutaneous  vessels  and 
nerves ;  as  the  superficial  epigastric  artery,  the  saphenous  veins, 
the  radial  and  ulnar  veins,  the  superficial  lymphatic  vessels,  or 
the  cutaneous  nerves,  and  in  one  instance  a  muscle,  platysma 
myoides. 

The  DEEP  FASCIA  is  a  dense  and  resisting  layer,  found  chiefly 
in  the  extremities  and  in  the  neck,  where  large  vessels  are  carry- 
ing onwards  the  circulating  fluids  in  opposition  to  the  laws  of 
gravity,  and  where  muscles  are  often  acting  with  prodigious  force. 
In  other  situations,  as  over  the  trunk  of  the  body  or  upon  the 
head,  this  layer  cannot  be  said  to  exist.  The  deep  fascia  in  the 
limbs  (aponeurotic  fascia)  is  a  white  fibrous  membrane,  formed 
by  a  close  interlacement  of  glistening  fibres,  which  cross  each 
other  in  various  directions.  To  the  eye  it  presents  a  brilliant, 
nacreous  lustre.  It  is  strong  and  unyielding,  inclosing  the  entire 
limb,  and  is  prolonged  into  its  substance  so  as  to  form  distinct 
sheaths  to  all  the  muscles.  Upon  the  inner  side  of  the  limb  it 
is  thin ;  on  the  outer  and  less  protected  side  it  is  dense  and  thick. 
It  is  connected  to  the  prominent  points  about  the  limb,  as  to  the 
pelvis,  knee,  and  ankle,  in  the  lower  extremity,  and  to  the  clavi- 
cle, scapula,  elbow,  and  wrist,  in  the  upper  extremity.  Its  ten- 
sion is  regulated  in  some  situations  by  muscular  action,  as  by  the 
tensor  vagina3  femoris  and  gluteus  maximus  in  the  thigh,  and  by 
the  biceps  and  palmaris  longus  in  the  arm.  The  deep  fascia  of 
the  neck  (cellulo-fibrous  fascia)  is  thinner,  and  has  none  of  the 
resplendency  of  that  of  the  limbs,  although  composed,  like  the 
latter,  of  white  fibrous  tissue. 

The  MUSCLES  (musculus,  from  movere,  to  move)  are  the  moving 
organs  of  the  body :  they  are  made  up  of  fibres  disposed  parallel 
to  each  other  in  a  framework  of  cellular  tissue.  Towards  the 
extremities  of  the  muscles  the  fibres  cease,  and  the  cellular  frame- 
work is  condensed  into  a  rounded  cord,  called  tendon  (tendo,  a 
sinew),  by  which  it  is  attached  to  the  bones.  The  more  fixed 
extremity  of  a  muscle  is  called  the  "origin  ;"  its  more  movable 
end  the  "insertion."  The  muscles  which  inclose  cavities,  as  the 
abdominal,  are  broad  arid  extensive;  and  their  tendon  is  flattened 
out  into  a  thin  expansion,  which  is  called  "  aponeurosis"  (a?to, 
longe  ;  **vpo»/,  nervus  ;  a  nerve  widely  spread  out).  This  deriva- 
tion demands  some  explanation.  The  ancients  named  all  the 
white  fibres  of  the  body  vrvpa,  or  nerves. 

The  VESSELS  ;ire  of  three  kinds,  arteries,  veins,  and  lym- 
phatics. Arteries  are  cylindrical  tubes,  composed  of  three  layers, 


28  THE   DISSECTOR. 

an  external,  formed  of  condensed  cellular  tissue,  the  cellulo-Jibrous 
coat ;  a  middle,  of  fibres  analogous  to  those  of  organic  muscle, 
the  contractile  coat ;  and  a  lining  membrane,  the  internal  or  serous 
coat.  After  death  they  are  usually  found  empty,  but  preserve 
their  cylindrical  form  by  reason  of  the  thickness  of  their  coats  ; 
hence  their  name  (a^p  typew,  to  contain  air),  from  a  supposition 
of  the  ancients  that  they  were  intended  to  confine  the  vital  spirits. 
Their  office  is  to  convey  the  vital  fluid  to  every  part  of  the  sys- 
tem ;  and  their  ultimate  terminations  are  denominated,  from  their 
extreme  minuteness,  capillaries  (capillus,  hair). 

The  veins  are  found  in  company  with  the  arteries;  with  the 
exception  of  the  superficial  veins.  They  return  the  blood  from 
the  capillary  vessels  of  the  arteries  to  the  right  side  of  the  heart, 
to  be  then  circulated  through  the  lungs.  They  are  larger  than 
the  arteries,  and  after  death  are  found  filled  with  dark-colored 
blood.  The  coats  are  the  same  as  those  of  the  arteries,  but  much 
thinner;  and  the  internal  coat  is  reflected  inwards  at  various 
points,  so  as  to  form  valves.  The  position  of  these  valves  is  evi- 
dently marked  on  the  exterior  of  the  tube,  by  the  swellings  on 
that  part  of  the  vessel  which  immediately  precedes  them. 

The  lymphatics  (lympha,  water)  are  small,  delicate  vessels 
which  accompany  the  veins,  and  present  many  points  of  resem- 
blance with  them.  They  return  a  limpid  fluid  to  the  venous 
circulation,  and  are  provided  with  a  number  of  valves  placed  at 
short  distances,  which,  with  the  corresponding  swellings,  give 
them  a  knotted  appearance.  Their  coats  are  the  same  as  those 
of  veins  and  arteries.  Near  the  flexures  of  the  joints  they  enter 
small  red  bodies,  called  glands,  from  which  they  emerge  fewer 
in  number,  and  larger  in  size.  They  are  too  minute  to  be  seen 
in  an  ordinary  dissection,  unless  the  subject  be  anasarcous. 

The  NERVES  (vfvpa,  nerves)  are  white  flattened  cords,  composed 
of  fibres,  which  are  connected  by  one  extremity  with  the  cerebro- 
spinal  axis  ;  and,  by  the  other,  are  distributed  to  all  the  textures 
of  the  body,  communicating  to  them  sensibility  and  power  of 
motion.  The  smallest  nerve  is  made  up  of  a  number  of  tubular 
fibres,  inclosed  in  a  peculiar  transparent  sheath,  called  neuri- 
lemma ;  which,  when  freshly  exposed,  presents  a  continuous 
zigzag  line  along  its  cylinder.  The  nerves  are  usually  found 
accompanying  the  arteries,  and,  in  the  extremities,  are  placed 
nearer  the  integument  than  those  vessels,  as  if  to  be  ready  to 
apprise  the  neighboring  muscles  of  the  first  approach  of  injury, 
that  they  may  withdraw  the  more  immediately  important  organs, 
the  arteries,  from  its  consequences. 

The  BONES  are  the  organs  of  support  to  the  animal  frame. 
They  give  firmness  and  strength  to  the  entire  fabric,  afford 
points  of  connection  to  the  numerous  muscles,  and  bestow 


BONES — LIGAMENTS.  29 

general  form  upon  the  body.  In  the  limbs  they  are  hollow 
cylinders,  calculated  by  their  form  and  structure  to  support 
weight,  and  resist  violence.  In  the  trunk  and  head,  they  are 
flattened  and  arched,  to  protect  cavities  and  provide  extensive 
surfaces  of  attachment.  In  many  situations  they  present  pro- 
jections of  considerable  length  that  serve  as  levers  ;  and  smooth 
surfaces  that  possess  all  the  mechanical  advantages  of  the  pulley. 
While  strength  and  solidity  are  the,  principal  objects  sought  for 
in  the  shaft  of  the  bone,  the  extremities  are  expanded  into  broad 
surfaces,  that  they  may  transmit  the  weight  of  the  body  with 
perfect  security  to  the  bones  below. 

In  the  formation  of  a  joint  a  new  organ  is  introduced,  the 
ligament  (ligare,  to  bind).  It  consists  of  short  strata  of  fibres 
passing  from  bone  to  bone,  in  order  to  connect  them  together. 
The  different  varieties  of  joint  demand  a  different  arrangement 
of  these  ligaments.  Thus  the  hinge  joint,  as  the  elbow,  wrist, 
knee,  ankle,  moving  in  one  direction  only,  has  necessarily  a 
squareness  of  form,  and  is  provided  with  a  ligament  to  each  of 
its  four  sides.  These  are  named  from  their  position,  anterior, 
posterior,  and  lateral.  A  great  proportion  of  the  joints  of  the 
body  are  constructed  upon  this  simple  principle.  When  more 
extensive  movements  are  demanded,  the  ball  and  socket  joint  is 
provided,  and  to  accommodate  its  circular  form,  the  four  liga- 
ments are,  as  it  were,  united  into  one,  which  completely  surrounds 
the  ends  of  the  two  bones.  Hence  the  capsular  ligaments  of 
the  hip,  the  shoulder,  and  the  thumb.  And  when  repose  and 
solidity  are  the  great  objects,  as  in  the  vertebral  column,  the 
pelvis,  the  carpus,  and  tarsus,  small  slips  of  ligaments  are  seen 
passing  from  bone  to  bone  in  every  direction  in  which  these 
straight  bands  can  be  arranged,  without  inconvenience  to  the 
general  plan. 

These,  then,  are  the  structures  of  which,  with  the  exception  of 
the  viscera,  the  whole  animal  frame  is  composed  ;  and  it  is 
incumbent  upon  the  student  of  anatomy  to  possess  a  clear  and 
distinct  idea  of  all  these  parts,  their  uses,  and  natural  dependen- 
cies, before  he  can  hope  to  display  and  examine  them  in  the  body 
with  advantage. 

[The  attention  of  the  dissector  should  also  be  directed  to  some 
general  facts  in  regard  to  the  position  of  certain  structures  and 
their  relative  importance  in  the  economy.  Thus  he  should  re- 
member that  the  great  bloodvessels  are  placed  upon  the  line  of 
flexion,  and  as  near  as  possible  towards  the  inner  side,  and  that 
this  line  includes  all  of  the  anterior  aspect  of  the  body,  with  the 
exception  of  the  legs.  By  this  arrangement,  these  essential 
parts  are  most  effectually  protected  from  injury,  an(l  least  ex- 
posed to  disturbance  frorn  the  movements  of  the  body.  Jle 

3* 


30  THE   DISSECTOR. 

should  also  not  lose  sight  of  the  ordinary  laws  of  physics  and 
mechanics  in  his  study  of  the  human  frame,  for,  by  an  intelligent 
application  of  these,  he  will  frequently  be  enabled  to  comprehend 
and  give  a  purpose  to  a  part  (as  of  a  muscle,  for  example)  even 
before  he  has  an  exact  idea  of  its  position  and  relations. 

The  dissector  should  furnish  himself  with  an  apron  with  sleeves, 
which  will  protect  his  clothes  from  the  contact  with  the  subject 
or  table,  and  a  case  of  dissecting  instruments.  This  case  must 
contain  from  three  to  six  scalpels  of  different  sizes,  a  tenaculum, 
a  double  hook,  a  pair  of  forceps,  a  couple  of  needles,  a  pair  of 
scissors,  and  a  cartilage  knife.  Every  other  requisite  is  usually 
furnished  by  the  rooms  in  which  the  student  dissects.  A  dis- 
sector in  the  country  must  provide  himself  in  addition  with 
several  large  sponges,  a  couple  of  blocks  of  different  sizes,  a  saw, 
and  a  mallet,  and  chisel. 

When  the  subject  is  injected  with  chloride  of  zinc,  a  plan 
generally  adopted  in  this  country,  care  should  be  taken  not  to 
remove  too  much  of  the  integument  at  once,  as  the  parts,  when 
exposed,  will  dry  and  become  hardened  very  rapidly,  and  will 
require  to  be  soaked  in  water,  in  order  to  be  again  fit  for  dis- 
section.] 


CHAPTER   II. 

ABDOMEN. 

[The  dissection  of  the  abdomen  is  to  he  commenced  by  an  incision 
from  the  lower  part  of  the  second  piece  of  the  sternum  down  the  median 
line  to  the  pubis ;  this  incision  must  be  carried  on  each  side  of  the  umbi- 
licus so  as  to  isolate  it.  A  second  incision  starts  from  the  upper  end  of 
the  first,  downwards  and  outwards,  forming  an  angle  with  the  first  of 
about  forty-five  degrees.  A  third  is  to  be  commenced  at  the  pubis  and 
carried  to  the  anterior  superior  spiuous  process  of  the  ilium,  and  from 
thence  around  the  crista  of  the  ilium  as  far  back  as  possible.  When  the 
skin  and  superficial  fascia  are  raised  from  the  central  line  outwards,  com- 
mencing at  the  upper  corner,  the  external  oblique  muscle  will  be  fully 
uncovered,  and  great  care  should  be  taken  not  to  get  beneath  its  tendon, 
the  white  shining  fibres  of  which  will  serve  as  a  guide  to  its  muscular  parts 
upon  the  thorax,  and  the  outer  side  of  the  abdominal  parietes.  These 
latter  incisions  must  be  repeated  on  the  opposite  side  of  the  subject.  The 
integument  alone  should  be  dissected  at  first,  leaving  the  superficial 
fascia,  and  after  this  has  been  studied  it  should  be  removed  in  the  di- 
rection of  the  fibres  of  the  muscle  and  of  its  aponeurosis.  One  side  of 


ABDOMEN.  31 

the  abdomen  should  be  dissected  exclusively  for  the  muscles,  and  on 
this  side  the  skin  and  fascia  may  be  taken  up  together ;  the  other 
should  be  reserved  for  studying  the  relations  of  hernia.] 

The  superficial  fascia  of  the  abdomen,  like  that  in  other  parts 
of  the  body,  is  composed  of  cellular  and  adipose  tissue.  The 
quantity  of  fat  varies  considerably  in  different  subjects.  Near 
the  groin  the  fascia  is  separable  into  two  layers,  between  which 
are  situated  the  superficial  vessels  and  some  inguinal  glands. 
The  superficial  layer,  in  which  the  fat  is  chiefly  found,  is  con- 
tinuous over  Poupart's  ligament  with  the  superficial  fascia  of 
the  thigh.  The  deep  layer  is  attached  to  Poupart's  ligament, 
and  is  lost  on  the  upper  part  of  the  fascia  lata.  It  contains  but 
little  fat,  and  is  cellulo-fibrous  in  structure.  The  superficial  fascia, 
divested  of  its  fat,  forms  a  sheath  for  the  spermatic  cord,  and  is 
prolonged  over  the  penis  and  scrotum  into  the  perineum,  where 
it  is  continuous  with  the  superficial  fascia  of  that  region. 

The  superficial  arteries  of  the  abdomen  are  the  superior  exter- 
nal pudic,  superficial  epigastric,  and  superficial  circumflexa  ilii, 
all  situated  in  the  groin  and  branches  of  the  femoral  artery ;  and 
cutaneous  branches  which  accompany  the  lateral  cutaneous  and 
anterior  cutaneous  nerves  ;  the  latter  being  derived  from  the  in- 
tercostals,  deep  epigastric,  and  internal  mammary  artery. 

The  superior  external  pudic  artery  crosses  the  external  abdo- 
minal ring  and  spermatic  cord,  and  is  distributed  to  the  integu- 
ment of  the  pubes  and  external  organs  of  generation. 

The  superficial  epigastric  lies  externally  to  the  external  abdo- 
minal ring,  and  ascends  towards  the  umbilicus,  supplying  the  in- 
tegument in  its  course,  and  inguinal  glands. 

The  superficial  circurnflexa  ilii  sends  one  or  two  small  branches 
to  the  integument  near  the  iliac  extremity  of  Poupart's  ligament. 

The  veins  accompanying  these  arteries  terminate  in  the  inter- 
nal saphenous  vein. 

The  superficial  nerves  of  the  abdomen  are  the  lateral  cutane- 
ous, anterior  cutaneous,  ilio-hypogastric,  and  ilio-inguinal. 

The  lateral  cutaneous  nerves,  five  or  six  in  number,  are  derived 
from  the  intercostal  nerves.  They  pierce  the  muscles  in  a  line 
with  the  thoracic  branches,  and  divide  like  them  into  an  anterior 
and  posterior  branch.  The  anterior  branch  is  continued  for- 
wards as  far  as  the  linea  semilunaris.  The  posterior  branch, 
smaller  than  the  anterior,  turns  backward  over  the  latissimus  dorsi 
muscle. 

The  lateral  cutaneous  branch  of  the  last  dorsal  nerve  is  an  ex- 
ception to  the  rest.  It  does  not  divide  after  piercing  the  exter- 
nal oblique  muscle,  but  is  directed  downwards  over  the  crest  of 
the  ilium,  and  is  distributed  to  the  integument  of  the  hip  as  low 


32  THE   DISSECTOR. 

down  as  the  trochanter  major.  The  nerve  crosses  the  crest  of 
the  ilium  just  behind  the  origin  of  the  tensor  vaginae  femoris. 

The  anterior  cutaneous  nerves  are  the  terminations  of  the  in- 
tercostal nerves ;  they  pierce  the  sheath  of  the  rectus  near  the 
linea  alba,  and  are  reflected  outwards  to  be  distributed  to  the  in- 
tegument. Like  the  lateral  cutaneous  nerves,  they  are  accom- 
panied by  small  arteries. 

The  ilio-hypogastric  nerve,  derived  from  the  first  lumbar  nerve, 
divides  into  an  iliac  and  hypogastric  branch.  The  iliac  branch 
pierces  the  muscles  just  above  the  crest  of  the  ilium  and  behind 
its  middle  point,  and  is  distributed  to  the  integument  of  the  glu- 
teal  region.  The  hypogastric  branch  pierces  the  aponeurosis  of 
the  external  oblique  above  the  external  abdominal  ring,  and  is 
distributed  to  the  integument  of  the  hypogastric  region. 

The  ilio-inguinal  nerve,  also  derived  from  the  first  lumbar  nerve, 
emerges  at  the  external  abdominal  ring,  and  is  distributed  to  the 
scrotum  and  upper  part  of  the  thigh,  internally  to  the  saphenous 
opening. 

The  lymphatic  glands,  three  or  four  in  number,  are  situated 
between  the  two  layers  of  the  superficial  fascia  above  Poupart's 
ligament.  They  receive  the  lymphatics  from  the  abdomen,  upper 
and  outer  part  of  the  thigh,  and  genital  organs  ;  and  their  efferent 
ducts  descend  to  the  saphenous  opening  to  enter  the  stream  of 
lymphatics  of  the  lower  limb. 

The  MUSCLES  of  the  abdomen  are  the 
External  oblique,  Rectus, 

Internal  oblique,  Pyramidal  is, 

Transversalis,  Quadratus  lumborum. 

When  the  external  oblique  muscle  is  dissected  on  both  sides,  a 
white  tendinous  line  will  be  seen  along  the  middle  of  the  abdo- 
men, extending  from  the  ensiform  cartilage  to  the  pubes  :  this  is 
the  linea  alba.  A  little  external  to  it,  on  each  side,  two  curved 
lines  will  be  observed  extending  from  the  eighth  rib  to  the  spine 
of  the  pubes,  and  bounding  the  recti  muscles:  these  are  the  linece 
semilunares.  Some  transverse  lines,  linece  transverse,  three  in 
number,  connect  the  lineae  semilunares  with  the  linea  alba  at  and 
above  the  umbilicus. 

The  linea  semilunaris  was  the  situation  formerly  chosen  for  the  opera- 
tion of  tapping  the  abdomen  in  dropsy,  paracentesis  abdominis.  But  being 
merely  the  outer  margin  of  a  muscle,  it  is  liable  to  alter  its  position  with 
the  expansion  to  which  the  whole  of  the  abdominal  muscles  are  subjected 
in  that  disease.  The  rectus  may,  in  this  way,  be  spread  over  the  whole 
anterior  half  of  the  abdomen,  and  the  linea  semilunaris  become  so  much 
displaced  as  hardly  to  be  discerned  by  external  examination.  Again,  the 
sheath  of  the  rectus  contains  a  large  artery  (epigastric)  ;  and  with  the 


MUSCLES   OP   THE   ABDOMEN. 
Fig.  1. 


33 


THE  MUSCLES  OF  THE  ANTERIOR  ASPECT  OF  THE  TRUNK;  ON  THE  LEFT 
SIDE  THE  SUPERFICIAL  LATER  is  SEEN,  AND  ON  THE  RIGHT  THE  DEEPER 
LAYER. — 1.  The  pectoralis  major  muscle.  2.  The  deltoid;  the  interval  between 
these  muscles  lodges  the  cephalic  vein.  3.  The  anterior  border  of  the  latissimus 
dorsi.  4.  The  serrations  of  the  serratus  magnus.  5.  The  subclavius  muscle  of 
the  right  side.  6.  The  pectoralis  minor.  7.  The  coraco-brachialis  muscle.  8. 
The  upper  part  of  the  biceps  muscle,  showing  its  two  heads.  9.  The  coracoid 
process  of  the  scapula.  10.  The  serratus  magnus  of  the  right  side.  11.  The 
external  intercostal  muscle  of  the  fifth  intercostal  space.  12.  The  external 
oblique  muscle.  13.  Its  aponeurosis;  the  median  line  to  the  right  of  this  num- 
ber is  the  linea  alba ;  the  flexuous  line  to  its  left  is  the  linea  semilunaris ;  and 
the  transverse  lines  above  and  below  the  number,  the  lineae  transversae,  of  which 
there  were  only  three  in  this  subject.  14.  Poupart's  ligament.  15.  The  exter- 
nal abdominal  ring ;  the  margin  above  the  ring  is  the  superior  or  internal  pillar; 
the  margin  below  the  ring,  the  inferior  or  external  pillar;  the  curved  inter- 
col  mnnar  fibres  are  seen  proceeding  upwardsfrom  Poupart's  ligament  to  strengthen 
the  ring.  The  numbers  14  and  15  are  situated  upon  the  fascia  lata  of  the  thigh  ; 
the  opening  immediately  on  the  right  of  15  is  the  saphenous  opening.  16.  The 
rectus  muscle  of  the  right  side  brought  into  view  by  the  removal  of  the  anterior 
segment  of  its  sheath ;  *  the  posterior  segment  of  its  sheath  with  the  divided 
edge  of  the  anterior  segment.  17.  The.  pyramidalis  muscle.  18.  The  internal 
oblique  muscle.  19.  The  conjoined  tendon  of  the  internal  oblique  and  trans- 
versalis  descending  behind  Poupart's  ligament  to  the  pectineal  line.  20.  The 
arch  formed  between  the  lower  curved  border  of  the  internal  oblique  muscle 
and  Poupart's  ligament;  it  is  ben  earth  this  arch  that  the  spermatic  cord  and 
hernia  pass.  21.  Fascia  lata  femoris.  22.  Saphenous  opening. 


34  THE   DISSECTOR. 

increased  breadth  of  the  muscle,  this  also  changes  its  course.  In  a  few 
instances  the  artery  has  been  wounded  in  consequence  of  this  change  of 
position,  and  the  operation  in  the  linea  semilunaris  is  therefore  abandoned. 
Ventral  hernia  may  occur  in  the  course  of  this  line. 

The  linea  alba  is  now  selected  for  the  operation  of  paracentesis  abdo- 
minis.  Being  in  the  middle  line  it  cannot  change  its  place  by  distension, 
and  there  is  no  risk  of  wounding  an  artery.  The  spot  selected  for  the 
operation  is  usually  midway  between  the  umbilicus  and  pubes.  It  is 
performed  by  making  a  small  incision  with  a  bistoury  through  the  inte- 
gument and  superficial  fascia,  and  then  introducing  the  trocar.  This 
line  is  also  the  seat  of  operation  for  puncturing  the  bladder  above  the 
pubes ;  which  is  performed  in  the  same  manner  as  paracentesis  abdo- 
minis. 

The  high  operation  for  lithotomy,  #  practice  disused  in  this  country,  has 
also  its  seat  in  the  linea  alba. 

The  Ccesarean  section,  for  opening  the  uterus  and  removing  the  fetus, 
an  operation  which  is  now  becoming  frequent  in  consequence  of  success  ; 
and  the  operation  for  the  removal  of  a  part  or  the  whole  of  the  cyst  in 
ovarian  dropsy,  are  also  practised  in  the  linea  alba. 

Moreover,  a  weakening  of  the  linea  alba,  from  over-distension,  or  con- 
genital deficiency,  gives  rise  to  the  protrusion  of  intestine  at  the  umbili- 
cus, called  umbilical  hernia. 

Deficiencies  of  development  also  occur  in  this  line,  in  which  some  of 
the  abdominal  viscera  are  exposed ;  the  most  frequent  instance  of  this 
arrest  is  in  the  case  where  the  mucous  membrane  of  the  bladder  is  pro- 
truded through  the  integument. 

The  EXTERNAL  OBLIQUE  MUSCLE  (oHiquus  externus  abdominis 
descendens)  is  the  external  flat  muscle  of  the  abdomen.  Its  name 
is  derived  from  the  obliquity  of  its  direction,  and  the  descend- 
ing course  of  its  fibres.  It  arises  by  fleshy  digitations  from 
the  external  surface  of  the  eight  inferior  ribs ;  the  five  upper 
digitations  being  received  between  corresponding  processes  of 
the  serratus  magnus,  and  the  three  lower  of  the  latissimus  dorsi. 
Soon  after  its  origin  it  spreads  out  into  a  broad  aponeurosis,  and 
is  inserted  into  the  outer  lip  of  the  crest  of  the  ilium  for  one-half 
its  length,  the  anterior  superior  spine  of  the  ilium,  spine  of  the 
os  pubis,  pectineal  line,  front  of  the  os  pubis,  and  linea  alba. 

The  superior  border  of  the  obliquus  externus  is  continuous 
with  the  lower  border  of  the  pectoralis  major,  and  its  fibres  of 
origin  with  those  of  the  external  intercostal  muscles.  Its  poste- 
rior border  is  separated  from  the  anterior  border  of  the  latissimus 
dorsi  by  a  cellular  interval,  but  is  sometimes  overlapped  by  that 
muscle. 

The  lower  border  of  the  aponeurosis,  which  is  stretched 
between  the  anterior  superior  spinous  process  of  the  ilium  and 
the  spine  of  the  os  pubis,  is  round  from  being  folded  inwards, 
and  forms  Pouparfs  ligament.  Poupart's  ligament  is  round  at  its 
outer  part,  but  flattened  from  above  downwards  nearer  the  pubes, 
forming  a  groove  which  supports  the  spermatic  cord.  It  is  curved 


EXTERNAL   OBLIQUE   MUSCLE. 


35 


in  its  course,  from  its  attach- 
ment to  the  fascia  lata ;  and 
its  insertion  into  the  pecti- 
neal  line  is  Gimbernafs  liga- 
ment. The  attachment  of 
Gimbernat's  ligament  to  the 
pectineal  line  is  about  three 
quarters  of  an  inch  in  length, 
and  from  this  insertion  some 
tendinous  fibres  are  directed 
upwards  and  inwards  behind 
the  rectus  muscle  to  the 
linea  alba,  and  have  received 
the  name  of  triangular  liga- 
ment. 

Just  above  the   crest  of 
the  os  pubis  is  the  external 
abdominal  ring,  a  triangu-        THE  INNOMINATE  BONE  OP  THE  LEFT 
lar  opening  formed  by  the    SIDB,   with-i.   Poupart's  ligament ;   2. 

r ,.       °  »      ,        «,    J         f     Orirabernat  s  ligament. 

separation  of  the  fibres  of 

the  aponeurosis  of  the  external  oblique.  It  is  oblique  in  its 
direction,  and  corresponds  with  the  course  of  the  fibres  of  the 
aponeurosis.  It  is  bounded  below  by  the  crest  of  the  os 
pubis ;  on  either  side,  by  the  borders  of  the  aponeurosis,  which 
are  called  pillars  ;  and  above  by  some  curved  fibres  (intercolum- 
nar)  which  originate  from  Poupart's  ligament,  and  cross  the 
upper  angle  of  the  ring,  so  as  to  give  it  strength.  The  exter- 
nal pillar,  which  is  at  the  same  time  inferior  from  the  obliquity 
of  the  opening,  is  inserted  into  the  spine  of  the  os  pubis ;  the  in- 
ternal or  superior  pillar  forms  an  interlacement  with  its  fellow  of 
the  opposite  side  over  the  front  of  the  symphysis  pubis.  The 
external  abdominal  ring  gives  passage  to  the  spermatic  cord  in 
the  male,  and  the  round  ligament  in  the  female:  they  are  both 
invested  in  their  passage  through  it  by  a  thin  fascia  derived  from 
the  edges  of  the  ring,  and  called  inter columnar  fascia ,  or  fascia 
spermatica.  The  pouch  of  inguinal  hernia,  in  passing  through 
this  opening,  receives  the  intercolumnar  fascia  as  one  of  its 
coverings. 

The  external  oblique  is  now  to  be  removed  by  making  an  incision  across 
the  ribs,  just  below  its  origin,  to  its  posterior  border;  and  another  along 
the  crest  of  the  ilium  to  the  anterior  superior  spine,  and  thence  trans- 
versely onwards  to  the  linea  alba.  The  muscle  may  then  be  turned  for- 
wards to  the  linea  alba,  or  removed  altogether.  The  lower  portion  of  the 
aponeurosis  should  now  be  turned  downwards,  and  left  for  subsequent 
examination. 

The  INTERNAL  OBLIQUE  MUSCLE  (obliquus  intermit  abdominis 
ascendens)  is  the  middle  flat  muscle  of  the  abdomen.  It  arises 


36  THE   DISSECTOR. 

from  the  outer  half  of  Poupart's  ligament,  from  the  middle  of  the 
crest  of  the  ilium  for  two-thirds  its  length,  and  by  a  thin  apo- 
neurosis  from  the  spinous  processes  of  the  lumbar  vertebrae.  Its 
fibres  diverge  from  their  origin,  so  that  those  from  Poupart's 
ligament  curve  downwards,  those  from  the  anterior  part  of  the 
crest  of  the  ilium  pass  transversely,  and  the  rest  ascend  obliquely. 
The  muscle  is  inserted  into  the  pectinea}  line  and  crest  of  the  os 
pubis,  linea  alba,  and  lower  borders  of  the  five  inferior  ribs. 

Along  the  upper  three-fourths  of  the  linea  semilunaris,  the  apo- 
neurosis  of  the  internal  oblique  separates  into  two  lamellae,  which 
pass  one  in  front  and  the  other  behind  the  rectus  muscle  to  the 
linea  alba,  where  they  are  inserted ;  along  the  lower  fourth,  the 
aponeurosis  passes  altogether  in  front  of  the  rectus  without  sepa- 
ration. The  two  layers,  which  thus  inclose  the  rectus,  form  for 
it  a  partial  sheath. 

The  lowest  fibres  of  the  internal  oblique  are  inserted  into  the 
pectineal  line  of  the  os  pubis  in  common  with  those  of  the  trans- 
Fig.  3. 


THE  INTERNAL  OBLIQUE  AND  TRANSVERSALIS  MUSCLE  IN  THE  INGUINAL 
REGION,  WITH  THE  BOUNDARIES  OP  THE  INGUINAL  CANAL. — The  aponeurosis  of 
the  external  oblique  muscle  having  been  divided  and  turned  down,  the  internal 
oblique  is  brought  into  view  with  the  spermatic  cord  escaping  beneath  its  lower 
edge.— 1.  Aponeurosis  of  the  external  oblique.  1'.  Lower  part  of  same  turned 
down,  2,  Internal  oblique  muscle.  3.  Spermatic  cord.  4.  Saphenous  vein. 


CREMASTER   MUSCLE.  3t 

vcrsalis  muscle.  Hence  the  tendon  of  this  insertion  is  called  the 
conjoined  tendon  of  the  internal  oblique  and  transversals.  This 
structure  corresponds  with  the  external  abdominal  ring,  and  forms 
a  protection  to  what  would  otherwise  be  a  weak  point  in  the  ab- 
domen. Sometimes  the  tendon  is  insufficient  to  resist  the  pres- 
sure from  within,  and  becomes  forced  through  the  external  ring ; 
it  then  forms  the  distinctive  covering  of  direct  inguinal  hernia. 

The  spermatic  cord  passes  beneath  the  arched  border  of  the  internal 
oblique  muscle,  between  it  and  Poupart's  ligament.  During  its  passage, 
some  fibres  are  given  off  from  the  lower  border  of  the  muscle,  which  ac- 
company the  cord  downwards  to  the  testicle,  and  form  loops  around  it ; 
this  is  the  cremaster  muscle.  In  the  descent  of  oblique  inguinal  hernia, 
which  travels  the  same  course  as  the  spermatic  cord,  the  cremaster  mus- 
cle forms  one  of  its  coverings. 

The  CREMASTER,  considered  as  a  distinct  muscle,  arises  from 
the  middle  of  Poupart's  ligament,  and  forms  a  series  of  loops 
upon  the  spermatic  cord.  A  few  of  its  fibres  are  inserted  into 
the  tunica  vaginalis ;  the  rest  ascend  along  the  inner  side  of  the 
cord,  to  be  inserted,  with  the  conjoined  tendon,  into  the  pectineal 
line  of  the  os  pubis. 

The  internal  oblique  muscle  is  to  be  removed  by  separating  it  from  its 
attachments  to  the  ribs  above,  and  the  crest  of  the  ilium  and  Poupart's 
ligament  below.  It  should  be  divided  behind  by  a  vertical  incision  ex- 
tending from  the  last  rib  to  the  crest  of  the  ilium,  as  its  lumbar  attach- 
ment cannot  at  present  be  examined.  The  muscle  is  then  to  be  turned 
forwards.  Some  degree  of  care  will  be  required  in  performing  this  dissec- 
tion from  the  difficulty  of  distinguishing  between  this  muscle  and  the  one 
beneath.  A  thin  layer  of  cellular  tissue  is  all  that  separates  them  for  the 
greater  part  of  their  extent.  There  will  also  be  found  between  them 
branches  of  the  intercostal  arteries  and  nerves,  the  ilio-inguinal  and  ilio- 
hypogastric  nerves,  and  near  the  crest  of  the  ilium  the  circumflexa  ilii 
artery,  which  ascends  between  the  two  muscles,  and  forms  a  valuable 
guide  to  their  separation.  Just  above  Poupart's  ligament  they  are  so 
closely  connected,  that  it  is  impossible  to  divide  them. 

The  TRANSVERSALIS  is  the  internal  flat  muscle  of  the  abdomen  ; 
it  is  transverse  in  the  direction  of  its  fibres,  as  is  implied  in  its 
name.  It  arises  from  the  outer  third  of  Poupart's  ligament,  from 
the  internal  lip  of  the  crest  of  the  ilium,  its  anterior  two-thirds; 
from  the  spinous  and  transverse  processes  of  the  lumbar  vertebrae, 
and  from  the  inner  surface  of  the  six  inferior  ribs,  indigitating 
with  the  diaphragm.  Its  lower  fibres  curve  downwards,  to  be 
inserted,  with  the  lower  fibres  of  the  internal  oblique,  into  the 
pectineal  line,  and  form  the  conjoined  tendon.  Throughout  the 
rest  of  its  extent  it  is  inserted  into  the  crest  of  the  os  pubis  and 
linea  alba.  The  lower  fourth  of  its  aponeurosis  passes  in  front 
of  the  rectus  to  the  linea  alba;  the  upper  three-fourths,  with  the 
posterior  lamella  of  the  internal  oblique,  behind  it. 

The  posterior  aponeurosis  of  the  transversalis  divides  into  three 
4 


THE   DISSECTOR. 


Fig.  4. 


lamellae  ;  anterior,  which  is  attached  to  the  bases  of  the  transverse 
processes  of  the  lumbar  vertebra ;  middle,  to  the  apices  of  the 
transverse  processes ;  and  posterior,  to  the  apices  of  the  spinous 
processes.  The  anterior  and  middle  lamella  inclose  the  quad- 
ratus  lumborum  muscle  ;  the  middle  and  posterior,  the  erector 
spinaB.  The  union  of  the  posterior  lamella  with  the  posterior 
aponeurosis  of  the  internal  oblique,  serratus  postlcus  inferior, 
and  latissimus  dorsi,  constitutes  the  lumbar  fascia. 

To  dissect  the  rectus  muscle,  its  sheath  should  he  opened  by  a  ver- 
tical incision  extending  from  over  the  cartilages  of  the  lower  ribs  to 

the  front  of  the  os  pubis.  The 
sheath  may  then  be  dissected  off 
and  turned  to  either  side ;  this  is 
easily  done  excepting  at  the  linese 
transversse,  where  a  close  adhesion 
subsists  between  the  muscle  and 
the  external  boundary  of  the  sheath. 
The  sheath  contains  the  rectus  and 
pyramidalis  muscle. 

The  RECTUS  MUSCLE  arises  by 
a  double  tendon  from  the  front 
and  crest  of  the  os  pubis,  and 
is  inserted  into  the  cartilages 
of  the  fifth,  sixth,  and  seventh 
ribs.  It  is  traversed  by  several 
tendinous  intersections,  called 
linese  transversae.  One  of  these 
is  situated  at  the  umbilicus,  one 
over  the  ensiform  cartilage, 
and  one  midway  between  these 
points;  when  a  fourth  exists, 
it  is  situated  below  the  umbili- 
cus. They  are  vestiges  of  the 
abdominal  ribs  of  reptiles,  and 
very  rarely  extend  completely 
through  the  muscle. 

The     PYRAMIDALIS     MUSCLE 

A  LATERAL  VIEW  OF  THE  TRUNK  OF  THE  BODY,  SHOWING  ITS  MUSCLES,  AND 
PARTICULARLY  THE  TRANSVERSALis  ABDOMiNis. — 1.  The  costal  origin  of  the 
latissimus  dorsi  muscle.  2.  The  serratus  magnus.  3.  The  upper  part  of  the 
external  oblique  muscle  divided  in  the  direction  best  calculated  to  show  the 
muscles  beneath  without  interfering  with  its  indigitations  with  the  serratus 
magnus.  4.  Two  of  the  external  intercostal  muscles.  5.  Two  of  the  internal 
intercostals.  6.  The  transversalis  muscle.  7.  Its  posterior  aponeurosis.  8.  Its 
anterior  aponeurosis,  forming  the  most  posterior  layer  of  the  sheath  of  the  rec- 
tus. 9.  The  lower  part  of  the  left  rectus  with  the  aponeurosis  of  the  transver- 
salis passing  in  front.  10.  The  right  rectus  muscle.  11.  The  arched  opening 
left  between  the  lower  border  of  the  transversalis  muscle  and  Poupart's  liga- 
ment, through  which  the  spermatic  cord  and  hernia  pass.  12.  The  gluteus 
maximus,  and  medius,  and  tensor  vaginae  femoris  muscles  invested  by  fascia  lata. 


RECTUS   MUSCLE  —  PYRAMIDALIS   MUSCLE — ACTIONS.      39 

arises  from  the  crest  of  the  os  pubis  in  front  of  the  rectus,  and 
is  inserted  into  the  linea  alba  about  midway  between  the  umbi- 
licus and  os  pubis.  It  is  inclosed  in  the  same  sheath  with  the 
rectus,  and  rests  against  the  lower  part  of  that  muscle.  It  is 
sometimes  wanting. 

The  rectus  may  now  be  divided  across  the  middle,  and  the  two  ends 
drawn  aside  for  the  purpose  of  examining  the  mode  of  formation  of  its 
sheath. 

The  sheath  of  the  rectus  is  formed,  in  front,  for  the  upper  three- 
fourths  of  its  extent,  by  the  aponeurosis  of  the  external  oblique 
and  the  anterior  lamella  of  the  internal  oblique,  and  behind  by 
the  posterior  lamella  of  the  internal  oblique  and  the  aponeurosis 
of  the  transversalis.  At  the  commencement  of  the  lower  fourth, 
the  posterior  wall  of  the  sheath  terminates  in  a  thin  curved  mar- 
gin, the  aponeuroses  of  the  three  muscles  passing  altogether  in 
front  of  the  rectus. 

ACTIONS. — The  external  oblique  muscle,  acting  singly,  would  draw  the 
thorax  towards  the  pelvis,  and  twist  the  body  to  the  opposite  side.  Both 
muscles  acting  together  would  flex  the  thorax  directly  on  the  pelvis. 
The  internal  oblique  of  one  side  draws  the  chest  downwards  and  out- 
wards :  both  together  bend  it  directly  forwards.  Either  transversalis 
muscle,  acting  singly,  will  diminish  the  size  of  the  abdomen  on  its  own 
side,  and  both  together  will  constrict  the  entire  cylinder  of  the  cavity. 
The  recti  muscles,  assisted  by  the  pyramidales,  flex  the  thorax  towards 
the  pelvis,  and  through  the  medium  of  the  lineae  transversae,  are  enabled 
to  act  when  their  sheath  is  curved  inwards  by  the  action  of  the  trans- 
versales.  The  pyramidales  are  tensors  of  the  linea  alba.  The  abdomi- 
nal are  expiratory  muscles,  and  the  chief  agents  of  expulsion ;  by  their 
action  the  foetus  is  expelled  from  the  uterus,  the  urine  from  the  bladder, 
faeces  from  the  rectum,  bile  from  the  gall-bladder,  ingesta  from  the  sto- 
mach and  bowels  in  vomiting,  and  mucus  and  irritating  substances  from 
the  bronchial  tubes,  trachea,  and  nasal  passages  during  coughing  and 
sneezing.  To  produce  these  efforts,  they  all  act  together.  Their  violent 
and  continued  action  produces  hernia ;  and,  acting  spasmodically,  they 
may  occasion  rupture  of  the  viscera. 

Vessels  and  Nerves. — The  VESSELS  of  the  abdominal  parietes 
are,  the  intercostal  and  lumbar  arteries ;  circumflexa  ilii ;  and,  in 
the  sheath  of  the  rectus,  the  epigastric  and  internal  mammary. 

The  intercostal  arteries  continue  their  course  from  the  lower 
intercostal  spaces  between  the  internal  oblique  and  transversalis 
muscle  ;  they  are  distributed  to  the  muscles,  and  inosculate  with 
the  lumbar  arteries,  internal  mammary,  and  epigastric. 

The  lumbar  arteries,  four  in  number  on  each  side,  are  branches 
of  the  abdominal  aorta.  Their  course  and  distribution  are  similar 
to  that  of  the  intercostals.  Each  artery,  between  the  transverse 
processes  of  the  vertebrae,  divides  into  a  dorsal  and  abdominal 
branch.  The  dorsal  branch  passes  backwards  for  the  supply  of 
the  spine  and  muscles  of  the  vertebral  column.  The  abdominal 
branch  advances  between  the  transversalis  and  internal  oblique 


40  THE   DISSECTOR. 

muscle  to  supply  the  parietes  of  the  abdomen.  These  branches 
inosculate  with  the  intercostal  arteries  above,  the  ilio-lumbar 
and  circumflexa  ilii  below,  and  the  internal  mammary  and  epigas- 
tric in  front. 

The  circurnflexa  ilii  artery  arises  from  the  external  iliac  artery 
close  to  Pou part's  ligament,  and  passes  outwards  behind  that 
ligament  to  the  crest  of  the  ilium,  and  along  the  crest  to  its  pos- 
terior part,  where  it  inosculates  with  the  ilio-lumbar  artery.  In 
its  course,  the  artery  pierces  the  crural  sheath,  and  then  lies  be- 
tween the  transversalis  muscle  and  fascia  ;  near  its  termination  it 
pierces  the  transversalis,  and  becomes  placed  between  it  and  the 
internal  oblique.  An  ascending  branch  is  given  off  near  the  an- 
terior superior  spine  of  the  ilium ;  this  branch  ascends  in  the  cel- 
lular interval  between  the  internal  oblique  and  transversalis,  and 
inosculates  with  the  other  arteries  of  the  parietes. 

The  epigastric  artery  arises  from  the  front  of  the  external  iliac 
artery  a  little  above  the  circumflexa  ilii ;  it  bends  inwards,  and 
then  ascends  obliquely  between  the  transversalis  fascia  and  peri- 
toneum to  the  lower  margin  of  the  sheath?of  the  rectus.  Pierc- 
ing the  transversalis  fascia,  it  enters  the  sheath  and  ascends  be- 
hind the  rectus  muscle  to  its  upper  part,  where  (in  the  substance 
of  the  muscle)  it  inosculates  with  the  internal  mammary  artery. 
In  the  first  part  of  its  course  the  artery  lies  internally  to  the  in- 
ternal abdominal  ring,  below  the  spermatic  cord,  and  above  the 
femoral  ring.  When  the  abdominal  parietes  are  examined  from 
within,  the  epigastric  artery  will  be  seen  to  form  a  prominent 
ridge,  which  divides  the  iliac  fossa  into  an  internal  and  external 
portion.  It  is  in  the  former  that  direct  inguinal  hernia  occurs  ; 
in  the  latter  oblique  inguinal  hernia. 

The  branches  of  the  epigastric  artery  are  : — 

A  cremasteric  branch  which  accompanies  the  spermatic  cord, 
and  after  supplying  the  cremaster  muscle  inosculates  with  the 
spermatic  artery. 

A  pubic  branch,  which  is  distributed  behind  the  pubes,  and 
sends  a  small  branch  of  communication  downwards  to  the  obtu- 
rator artery. 

Muscular  branches,  which  pass  outwards  between  the  abdomi- 
nal muscles,  and  inosculate  with  the  circumflexa  ilii,  lumbar,  and 
intercostal  arteries. 

Superficial  branches,  which  are  distributed  to  the  integument 
of  the  abdomen. 

The  internal  mammary  artery,  a  branch  of  the  subclavian,  is 
situated  in  the  sheath  of  the  rectus.  It  supplies  the  upper  part 
of  that  muscle,  and  inosculates  with  the  epigastric,  intercostals, 
and  lumbar  arteries. 

The  VEINS  accompanying  the  arteries  of  the  abdominal  parietes 


EPIGASTRIC   ARTERY.  41 

take  the  course  of  their  respective  arterial  branches ;  the  inter- 
costal veins  terminate  in  the  venae  azygos,  the  lumbar  in  the  in- 
ferior vena  cava,  and  the  circumflexa  ilii  and  epigastric  in  the 
external  iliac. 

The  NERVES  of  the  abdominal  parietes  are,  the  six  lower  inter- 
Fig.  5. 


ANTERIOR  WALL  OF  THE  ABDOMEN  ;  INTERNAL  ASPECT. — a,  a,  Linea 
alba,  b,  b.  Linea  semilunaris.  c,  c.  Lineaa  transversae.  The  letters  c,  c  are 
placed  on  the  posterior  surface  of  the  sheath  of  the  rectus.  d.  The  lower  bor- 
der of  this  sheath,  under  which  T;he  epigastric  artery  is  seen  passing,  e,  /  The 
rectus  muscle  :  e  refers  also  to  the  superior  epigastric  artery,  a  branch  of  the 
internal  mammary  ;  and/, /to  the  proper  epigastric  artery,  g.  The  internal 
mammary  artery,  h.  Its  musculo-phrenic  branch,  t,  i.  Part  of  the  dia- 
phragm, k.  Section  of  the  three  abdominal  muscles.  /.  Section  of  the  exter- 
nal and  internal  oblique  ;  the  transversalis  having  been  removed,  m.  The  ex- 
ternal iliac  artery,  n.  The  circumflexa  ilii  artery,  seen  in  its  whole  course  on 
the  right  side  in  consequence  of  the  removal  of  the  transversalis  muscle  ;  the 
leading  line  crosses  the  iliacus  muscle,  u.  The  external  iliac  vein.  p.  The 
crural  ring.  g.  Gimbernat's  ligament,  s,  t,  refer  to  the  arch  formed  between 
the  lower  borders  of  the  internal  oblique  and  transversalis  muscle  and  Poupart's 
ligament ;  the  arch  is  crossed  by  the  epigastric  artery  :  the  space  s  above  the 
artery  corresponds  with  the  internal  abdominal  ring,  and  gives  passage  to  ob- 
lique inguinal  hernia  :  in  this  space  is  seen  a  part  of  the  internal  oblique  muscle, 
which  extends  lower  on  Poupart's  ligament  than  the  transversalis.  Through  the 
space  t  is  seen  the  aponeurosis  of  the  external  oblique  muscle,  v.  The  con- 
joined tendon  of  the  internal  oblique  and  transrersalis. 

4* 


42  THE   DISSECTOR. 

costals,  and  two  branches  of  the  first  lumbar  nerve,  namely,  the 
ilio-hypogastric,  and  ilio-inguinal. 

The  intercostal  nerves  pass  from  the  intercostal  spaces,  be- 
tween the  internal  oblique  and  transversalis  muscle,  to  the  front 
of  the  abdomen,  where  they  enter  the  sheath  of  the  rectus.  Near 
the  linea  alba  they  terminate  by  piercing  the  sheath,  and  becom- 
ing the  anterior  cutaneous  nerves  (page  32). 

Midway  between  the  vertebral  column  and  linea  alba,  each  in- 
tercostal nerve  gives  off  its  lateral  cutaneous  branch,  which  pier- 
ces the  internal  and  external  oblique  muscles  to  reach  the  sur- 
face (page  31). 

The  last  intercostal,  or  rather,  the  last  dorsal  nerve,  lies  below 
the  last  rib  ;  its  lateral  cutaneous  branch  does  not  divide  like  the 
rest,  but  is  continued  over  the  crest  of  the  ilium,  to  the  integu- 
ment of  the  hip. 

The  ilio-hypogastric  nerve  pierces  the  transversalis  just  above 
the  crest  of  the  ilium,  and  a  little  posterior  to  its  mid-point,  and 
divides  into  its  two  branches,  iliac  and  hypogastric.  The  iliac 
branch  pierces  the  internal  and  external  oblique  muscles,  and 
descends  over  the  crest  of  the  ilium,  to  be  distributed  to  the  in- 
tegument of  the  gluteal  region. 

The  hypogastric  branch  continues  its  course  forward,  a  little 
above  the  crest  of  the  ilium ;  and,  near  the  anterior  superior  spine, 
communicates  with  the  ilio-inguinal  nerve.  It  then  pierces  the 
internal  oblique  muscle,  and,  near  the  linea  alba,  the  aponeurosis 
of  the  external  oblique,  and  is  distributed  to  the  integument  of 
the  hypogastric  region. 

The  ilio-inguinal  nerve,  smaller  than  the  preceding,  and  infe- 
rior to  it  in  position,  pierces  the  transversalis  muscle  in  front  of 
the  anterior  superior  spine  of  the  ilium,  and  communicates  with 
the  hypogastric  branch  of  the  ilio-hypogastric  nerve.  It  then 
pierces  the  internal  oblique  muscle,  and,  passing  through  the 
external  abdominal  ring  with  the  spermatic  cord,  is  distributed 
to  the  integument  of  the  upper  and  itfner  part  of  the  thigh,  and 
to  the  neighboring  part  of  the  scrotum  or  pudendum. 

The  vessels  and  nerves  of  the  abdominal  parietes  having  been  carefully 
studied,  the  dissector  should  examine  the  lower  border  of  the  transver- 
salis muscle,  and  its  relations  to  the  internal  oblique  muscle  (which  has 
been  already  turned  aside,  but  may  be  replaced  for  this  examination) 
and  to  the  spermatic  cord.  The  latter  will  be  found  issuing  from  beneath 
the  lower  border  of  the  muscle,  between  it  and  Poupart's  ligament. 
Following  the  curve  formed  by  the  lower  border  of  the  muscle,  he  will 
find  it  descend  behind  the  spermatic  cord  and  Poupart's  ligament,  to  be 
inserted,  in  conjunction  with  the  internal  oblique  muscle,  into  the  pec- 
tineal  line  of  thepubes  behind  Grimbernat's  ligament.  The  membranous 
structure  which  occupies  the  interval  between  the  lower  border  of  the 
transversalis  and  Poupart's  ligament  is  the  transversalis  fascia,  which  is 
next  to  be  examined.  For  this  purpose  the  transversalis  should  be  sepa- 


FASCIA   TRANSVERSALI8. 


43 


Fig.  6. 


rated  from  its  attachment  to  Poupart's  ligament,  and  the  crest  of  the 
ilium,  and  turned  upwards  and  forwards;  the  muscle  should  then  be  di- 
vided by  an  incision  carried  from  the  middle  of  the  crest  of  the  ilium  to 
the  last  rib,  and  another  bordering  the  lower  margin  of  the  thorax. 
The  muscle  may  then  be  turned  over  entirely  to  the  middle  line,  and  the 
transversalis  fascia  will  be  exposed. 

The  fascia  transversalis  (fascia 
Cooperi — from  its  important  rela- 
tion to  inguinal  hernia  being  first 
particularly  described  by  Sir  Ast- 
ley  Cooper)  is  a  thin  fibrous  mem- 
brane which  lines  the  internal  sur- 
face of  the  transversalis  muscle, 
and  is  interposed  between  that 
muscle  and  the  peritoneum.  It 
is  thickest  at  the  lower  part  of 
the  abdomen  where  the  muscular 
structure  is  weak,  and  becomes 
thinner  as  it  ascends,  until  it  is 
lost  in  the  subserous  cellular  tissue. 
It  is  attached  inferiorly  to  the  re- 
flected margin  of  Poupart's  liga- 
ment, and  to  the  crest  of  the  ilium ; 
internally,  to  the  pectineal  line  and 
border  of  the  rectus  muscle  ;  and, 
at  the  inner  part  of  the  femoral 
arch,  is  continued  beneath  Pou- 
part's ligament,  and  forms  the  an- 
terior segment  of  the  crural  canal, 
or  sheath  of  the  femoral  vessels. 


THE  TRANSVERSALIS  FASCIA, 
THE  ABDOMINAL  MUSCLES  BEING 
REMOVED. — 1.  Poupart's  ligament. 
2.  The  transversalis  fascia.  3.  The 
internal  abdominal  ring,  an  open- 
ing in  the  transversalis  fascia.  4. 


The   internal   abdominal  ring  is     The  situation  of  the  external  ab- 

situated  in  this  fascia,  at  about  ^nal  &5^trSf2taS 
midway  between  the  symphysis  trie  artery  between  the  two  rings. " 
pubis  and  the  anterior  superior 

spine  of  the  ilium,  and  fralf  an  inch  above  Poupart's  ligament ; 
it  is  oval  in  form,  and  bounded  on  its  inner  side  by  a  well-marked 
falciform  border,  but  is  ill-defined  around  its  outer  margin.  From 
the  circumference  of  the  ring  is  given  off  an  infundibuliform 
process,  which  surrounds  the  testicle  and  spermatic  cord,  consti- 
tuting the  fascia  propria  of  the  latter,  and  forms  the  first  invest- 
ment to  the  sac  of  oblique  inguinal  hernia. 

When  the  fascia  propria  has  been  carefully  examined,  it  should  be 
laid  open  by  a  longitudinal  incision ;  this  will  bring  into  view  a  layer  of 
subserous  fat,  of  variable  thickness.  When  the  fat  is  pushed  aside  with 
the  handle  of  the  scalpel,  the  peritoneum  will  be  found  to  bulge  at  this 
point,  and  at  the  most  prominent  part  of  the  bulge  may  be  detected  the 
librous  remains  of  the  obliterated  process  of  the  peritoneum,  which  ori- 


44  THE   DISSECTOR. 

ginally  surrounded  the  testis  during  its  descent  in  the  foetus.  This 
fibrous  structure  may  present  every  degree  of  degradation;  sometimes  it 
is  scarcely  discernible,  at  other  times  it  is  a  fibrous  band  of 'some  bulk  ; 
in  another  series  of  cases  it  is  sacculated,  or  the  tube  of  peritoneum  may 
still  be  pervious. 

SPERMATIC  CORD. — The  spermatic  cord,  composed  of  the  ves- 
sels, nerves,  and  excretory  duct  of  the  testicle,  and  inclosed  by 
certain  coverings,  takes  its  course  from  the  internal  abdominal 
ring,  between  the  layers  constituting  the  parietes  of  the  abdo- 
men, to  the  external  abdominal  ring.  The  space  so  occupied 
by  the  spermatic  cord  is  denominated  the  spermatic  canal,  and 
is  about  one  inch  and  a  half  in  length.  It  is  bounded  in  front 
by  the  aponeurosis  of  the  external  oblique  muscle;  behind,  by 
the  transversalis  fascia,  and  the  conjoined  tendon  of  the  internal 
oblique  and  transversalis ;  above,  by  the  arched  borders  of  the 
internal  oblique  and  transversalis;  below,  by  the  grooved  border 
of  Poupart's  ligament:  and  at  each  extremity  by  one  of  the  ab- 
dominal rings,  the  internal  ring  at  the  internal  termination,  the 
external  ring  at  the  outer  extremity. 

The  coverings  of  the  spermatic  cord,  while  situated  in  the 
spermatic  canal,  are  the  fascia  propria,  derived  from  the  fascia 
transversalis;  and  the  cremaster  muscle,  derived  from  the  lower 
border  of  the  internal  oblique.  On  emerging  at  the  external 
abdominal  ring,  it  receives  the  intercolumnar  fascia  from  the 
borders  of  the  ring,  and  is  then  inclosed  in  a  sheath  of  superficial 
fascia;  lastly,  it  is  covered  by  the  integument. 

The  fascia  propria,  derived  from  the  fascia  transversalis,  is  an 
infundibuliform  sheath,  loosely  connected  with  the  cord  by  cel- 
lular tissue,  in  which  adipose  matter  is  deposited.  The  fibres  of 
the  cremaster  muscle,  held  together  by  cellular  tissue,  and  thus 
forming  a  cellulo-muscular  layer,  has  received  the  name  of 
cremasteric  fascia ;  and  the  intercolumnar  fascia  is  also  known 
as  the  spermatic  fascia. 

The  coverings  of  the  cord  may  now  be  divided  longitudinally,  and 
turned  aside,  in  order  to  bring  into  view  its  other  components,  the  ves- 
sels, nerves,  and  excretory  duct. 

The  ARTERIES  of  the  spermatic  cord  are  the  cremasteric,  sper- 
matic, and  deferential. 

The  cremasteric  artery  is  a  small  branch  of  the  epigastric,  and 
is  distributed  to  the  cremasteric  fascia. 

The  spermatic  artery,  a  branch  of  the  aorta,  enters  the  inter- 
nal abdominal  ring,  and  accompanies  the  cord  to  the  testicle,  to 
which  it  is  distributed. 

The  deferential  artery  is  a  small  branch  of  the  superior  vesical 
artery,  which  accompanies  the  vas  deferens  to  the  testicle. 

The  VEINS  of  the  cord,  the  spermatic  veins,  ascend  from  the 
posterior  border  of  the  testicle.  They  form  &  plexus  which  con- 


ANATOMY  OP  HERNIA. 


45 


stitutes  the  chief  bulk  of  the  cord,  and  unite  in  a  single  vein, 
which  accompanies  the  spermatic  artery  to  terminate  on  the  right 
side  in  the  inferior  vena  cava,  and  on  the  left  in  the  left  renal 
vein. 

The  lymphatic  vessels  of  the  spermatic  cord  terminate  in  the 
lumbar  glands. 

The  NERVES  of  the  spermatic  cord  are  the  scrota!  branch  of 
the  ilio-inguinal ;  the  genital  branch  of  the  genito-crural,  which 
enters  the  internal  abdominal  ring  and  accompanies  the  cremas- 
teric  artery  to  be  distributed  to  the  cremasteric  fascia;  and  the 
spermatic  plexus.  The  spermatic  plexus  is  derived  from  the 
aortic  and  renal  plexus,  and  accompanies  the  spermatic  artery. 

The  VAS  DEFERENS,  the  excretory  duct  of  the  testis,  is  situated 
along  the  posterior  border  of  the  cord,  where  it  may  be  distin- 
guished by  the  hard  and  cordy  sensation  which  it  communicates 
to  the  fingers.  On  reaching  the  internal  abdominal  ring,  it  lies 
internally  to  the  spermatic  vessels,  and  turns  inwards  behind  the 
epigastric  artery  to  the  side  and  base  of  the  bladder,  where  it 
terminates  in  the  urethra.  It  is  accompanied  by  its  proper 
artery. 

In  the  female,  the  place  Fig.  7. 

of  the  spermatic  cord  is 
occupied  by  the  round 
ligament  of  the  uterus, 
which  takes  exactly  the 
same  course  as  the  cord, 
has  the  same  relations 
and  coverings,  with  the 
exception  of  the  cremas- 
ter,  and,  after  passing 
through  the  external  ab- 
dominal ring,  terminates 
in  the  superficial  fascia 
of  the  groin. 

ANATOMY  OF  HERNIA. 

The  herniae  occurring 
in  the  parietes  of  the  ab- 
domen have  been  divided 
by  Sir  Astley  Cooper  into 
four  species;  namely,  um- 

THE  ANATOMY  OF  INGUINAL  HEUNIA,  THK  LEFT  INGUINAL  REGION.  THE 
APONEUROSIS  OF  THE  EXTERNAL  OBLIQUE  MUSCLE  AND  THE  FASCIA  LATA. — 
1.  The  internal  pillar  of  the  abdominal  ring.  2.  The  external  pillar  of  same 
(Pouparfs  ligament).  3.  Transverse  fibres  of  the  aponeurosis.  4.  Pectineal 
portion  of  the  fascia  lata.  5.  The  spermatic  cord.  6.  The  long  saphenous 
vein.  7.  Fascia  lata  feuioris;  its  sartorial  portion. 


46  THE  DISSECTOR. 

bilical,  ventral,  inguinal,  and  femoral:  to  which  may  be  added, 
as  occasionally  taking  place,  phrenic,  obturator,  ischiatic,  gluteal, 
perineal,  and,  in  the  female,  vaginal. 

Umbilical  hernia  occurs  at  the  umbilicus  from  weakening  of 
the  linea  alba,  either  by  over-distension,  as  in  utero-gestation,  or 
from  congenital  deficiency.  Its  coverings  are,  the  integument, 
superficial  fascia,  distended  aponeurosis,  and  peritoneum. 

Ventral  hernia  occurs  chiefly  in  the  linea  semilunaris,  and  from 
the  same  causes:  its  coverings  are  the  same,  but  it  has  usually 
three  layers  of  aponeurosis. 

Fig.  8. 


AFTER  THE  REMOVAL  OP  THE  LOWER  PART  OP  THE  EXTERNAL  OBLIQUE 
(WITH  THE  EXCEPTION  OP  A  SMALL  SLIP  INCLUDING  POUPART!S  LlGAMENT), 
THE  LOWER  PORTION  OF  THE  INTERNAL  OBLIQUE  WAS  RAISED,  AND  THEREBY 
THE  TRANSVERSALIS  MUSCLE  AND  FASCIA  HAVE  BEEN  BROUGHT  INTO  VIEW. 
THE  FEMORAL  ARTERY  AND  VEIN  ARE  SEEN  TO  A  SMALL  EXTENT,  THE  FASCIA 
LATA  HAVING  BEEN  TURNED  ASIDE  AND  THE  SHEATH  OP  THE  BLOODVESSELS 
LAID  OPEN. — 1.  External  oblique  muscle.  2.  Internal  oblique.  2'.  Part  of 
same  turned  up.  3.  Transversalis  muscle.  Upon  the  last-named  muscle  is 
seen  a  branch  of  the  circumflex  iliac  artery,  with  its  companion  veins ;  and 
some  ascending  tendinous  fibres  are  seen  over  the  conjoined  tendon  of  the  two 
last-named  muscles.  4.  Transversalis  fascia.  5.  Spermatic  cord  covered  with 
the  infundibuliform  fascia  from  preceding.  6.  Upper  angle  of  the  pectineal  part 
of  fascia  lata.  7.  The  sheath  of  the  femoral  vessels.  8.  Femoral  artery.  9. 
Femoral  vein.  10.  Saphenous  vein.  11.  A  vein  joining  it. 


OBLIQUE   INGUINAL   HERNIA. 


Inguinal  hernia  is  of  two  kinds,  oblique  and  direct:  the  former 
takes  the  course  of  the  spermatic  canal,  descending  by  the  side 
of  the  spermatic  cord.  The  latter  (direct)  pushes  directly  through 
the  external  abdominal  ring,  carrying  before  it  the  conjoined 
tendon  of  the  internal  oblique  and  transversalis  muscles. 

One  side  of  the  abdomen  having  been  reserved  for  the  study  of  hernia, 
an  incision  should  be  made  through  the  aponeurosis  of  the  external 
oblique  from  the  anterior  superior  spine  of  the  ilium  to  the  linea  alba, 
and  another  along  the  margin  of  Poupart's  ligament  to  the  external  pil- 
lar of  the  external  abdominal  ring.  The  aponeurosis  should  then  be 
drawn  down,  and  the  internal  oblique  muscle  and  transversalis  dissected 
separately  and  turned  aside  in  a  similar  manner.  The  transversalis 
fascia  and  peritoneum  should  next  be  divided  in  the  direction  of  the 
transverse  incision  from  the  crest  of  the  ilium  to  the  linea  alba.  The 
student  may  now  follow  the  description  of  inguinal  hernia,  and  examine 
the  layers  concerned  in  its  course. 

Fig.  9. 


A  DIRECT  INGUINAL  HERNIA 
ON  THE  LEFT  SIDE,  COVERED 
BV  THK  CONJOINED  TENDON  OF 
THE  INTERNAL  OBLIQUE  AND 
TRANSVERSE  MUSCLES.  —  1. 
Aponeurosis  of  the  external 
oblique.  2.  Internal  oblique 
turned  up.  3.  Transversalis 
muscle.  4.  Fascia  transversa- 
lis. 5.  Spermatic  cord.  6. 
The  hernia. — N.  B.  A  small 
part  of  the  epigastric  artery  is 
seen  through  an  opening  made 
in  the  transversalis  fascia. 


In  OBLIQUE  INGUINAL  HERNIA,  the  intestine  escapes  from  the 
cavity  of  the  abdomen  into  the  spermatic  canal,  through  the  in- 
ternal abdominal  ring,  pressing  before  it  a  pouch  of  peritoneum, 
which  constitutes  the  hernial  sac,  and  distending  the  infundibuli- 
form  process  of  the  transversalis  fascia.  After  emerging  through 
the  internal  abdominal  ring,  it  passes  fast  beneath  the  lower  and 
arched  border  of  the  transversalis  muscle;  then  beneath  the  lower 
border  of  the  internal  oblique  muscle;  and  finally  through  the 
external  abdominal  ring  in  the  aponeurosis  of  the  external  oblique. 
From  the  transversalis  muscle  it  receives  no  investment;  while 


48 


THE   DISSECTOR. 


passing  beneath  the  lower  border  of  the  internal  oblique,  it  ob- 
tains the  creraaster  muscle;  and,  upon  escaping  at  the  external 
abdominal  ring,  receives  the  intercolumnar  fascia.  So  that  the 
coverings  of  an  oblique  inguinal  hernia,  after  it  has  emerged 


Fig.  10. 


A  SMALL  OBLIQUE  INGUINAL 
HERNIA,  AND  A  DIRECT  ONE  ARE 
SEEN  ON  THE  RIGHT  SIDE.  A 
LITTLE  OP  THE  EPIGASTRIC  AR- 
TERY HAS  BEEN  LAID  BARE,  BY 
DIVIDING  THE  FASCIA  TRANSVER- 
SALIS  IMMEDIATELY  OVER  IT. — • 
1.  Tendon  of  the  external  ob- 
lique. 2.  Internal  oblique  turned 
up.  3.  Transversalis.  4.  Its 
tendon  (the  epigastric  artery  is 
shown  below  this  number).  5. 
The  spermatic  cord  (its  vessels 
separated).  6.  A  bubonocele. 
7.  Direct  hernia  protruded  be- 
neath the  conjoined  tendon  of 
the  two  deeper  muscles,  and  co- 
vered by  an  elongation  from  the 
fascia  transversalis. 


through  the  external  abdominal  ring,  are,  from  the  surface  to  the 
intestine,  the 

Integument, 

Superficial  fascia, 

Intercolumnar  fascia, 

Cremaster  muscle, 

Transversalis,  or  infundibuliform  fascia, 

Peritoneal  sac. 

There  are  three1  varieties  of  oblique  inguinal  hernia:  common, 
congenital,  and  encysted. 

Common  oblique  hernia  is  that  which  has  been  described 
above. 

Congenital  hernia  results  from  the  non-closure  of  the  pouch  of 
peritoneum  carried  downwards  into  the  scrotum  by  the  testicle 
during  its  descent  in  the  foetus.  In  consequence  of  this  defect,, 
the  intestine  at  some  period  of  life  is  forced  into  the  peritoneal 
canal,  and  descends  through  it  into  the  tunica  vaginalis,  where 
it  lies  in  contact  with  the  testicle  ;  so  that  congenital  hernia  has 

1  Verpeau  describes  a  fourth,  in  which  the  protrusion  takes  place  be- 
tween the  edge  of  the  rectus  and  the  umbilical  ligament,  and  then  takes 
the  course  of  the  spermatic  canal. 


DIRECT   INGUINAL   HERNIA. 


49 


no  proper  sac,  but  is  contained  within  the  tunica  vaginalis.    The 
other  coverings  are  the  same  as  those  of  common  inguinal  hernia. 


Fig.  11. 


Fig.  12. 


COMMON  OBLIQUE  INGUINAL  HER- 
NIA. THK  INTKSTINK  IN  A  DISTINCT 
SAC  OF  PERITONEUM  AND  SEPA- 
RATED FROM  THE  TESTICLE  BY  THE 
TUNICA  VAGINALIS. — 1.  The  sac  of 
the  hernia.  2.  The  tunica  vaginalis 
inclosing  the  testicle.  3,  4.  The 
spermatic  cord. 


CONGENITAL  HERNIA,  THE  INTES- 
TINE   BEING    IN    CONTACT    WITH    THE 

TESTICLE  ;  THE  TUNICA  VAGINALIS 
OF  THE  TESTICLE  FORMING  THE  SAC 
OF  THE  HERNIA. — 1.  The  tunica  va- 
ginalis testis,  continuous  superiorly 
with  the  peritoneum,  of  which  it  is  a 
part.  2.  The  testicle.  3.  The  sper- 
matic cord. 


Encysted  hernia1  (hernia  infantilis  of  Hey)  is  that  form  of 
protrusion  in  which  the  pouch  of  peritoneum  forming  the  tunica 
vaginalis,  being  only  partially  closed,  and  remaining  open  exter- 
nally to  the  abdomen,  admits  of  the  hernia  passing  into  the  scro- 
tum, behind  the  tunica  vaginalis.  So  that  the  surgeon,  in  ope- 
rating upon  this  variety,  requires  to  divide  three  layers  of  serous 
membrane  ;  the  first  and  second  layers  being  those  of  the  tunica 
vaginalis,  and  the  third  the  true  sac  of  the  hernia. 

DIRECT  INGUINAL  HERNIA  has  received  its  name  from  passing 
directly  through  the  external  abdominal  ring,  and  forcing  before 
it  the  opposing  parietes.  This  portion  of  the  wall  of  the  abdo- 
men is  strengthened  by  the  conjoined  tendon  of  the  internal 
oblique  and  transversalis  muscle,  which  is  pressed  before  the  her- 
nia, and  forms  one  of  its  investments.  Its  coverings  are,  the — 

1  A  case  of  this  kind  occurred  to  Mr.  Listen  in  1855.     The  student  will 
find  a  full  acconnt  of  it  in  a  Clinical  Lecture  in  the  1st  volume  of  the  Lan- 
cet for  1834—5,  page  883. 
5 


50 


THE   DISSECTOR. 


Fig.  13.  Integument, 

Superficial  fascia, 
Intercolumnar  fascia, 
Conjoined  tendon, 
Transversalis  fascia, 
Peritoneal  sac. 

Direct  inguinal  hernia  differs 
from  oblique,  firstly,  in  never  at- 
taining the  same  bulk,  in  conse- 
quence of  the  resisting  nature  of 
the  conjoined  tendon  of  the  inter- 
nal oblique  and  transversalis,  and 
of  the  transversalis  fascia;  secondly, 
in  its  direction,  having  a  tendency 
to  protrude  from  the  middle  line, 
rather  than  towards  it ;  thirdly,  in 
making  for  itself  a  new  passage 
through  the  abdominal  parietes, 
instead  *.of  following  a  natural 
channel;  and  fourthly,  in  the  re- 
lation of  the  neck  of  its  sac  to  the 
epigastric  artery,  that  vessel  lying 
to  the  outer  side  of  the  opening  of 
the  sac  of  direct  hernia,  and  to  the 
inner  side  of  that  of  oblique  hernia. 
All  the  forms  of  inguinal  hernia 

are  designated  scrotal,  when  they  have  descended  into  that  cavity. 
Oblique  inguinal  hernia,  in  its  course  through  the  spermatic 
canal,  lies  above  the  spermatic  cord.  In  rare  cases  the  hernial 
protrusion  may  separate  the  components  of  the  cord,  so  that 
some  of  them  may  lie  in  front  of  the  tumor :  hence  one  of  many 
reasons  for  extreme  care  and  caution  in  operating  for  strangu- 
lated hernia.  Direct  inguinal  hernia  often  carries  the  spermatic 
cord  before  it,  so  that  the  vessels  of  which  it  is  composed  be- 
come spread  over  the  front  of  the  hernial  sac,  or  slip  to  one  side. 
In  operating  upon  inguinal  hernia,  the  importance  of  knowing 
the  layers  which  cover  it,  and  which  are  to  be  cut  through  be- 
fore reaching  the  bowel,  is  obvious;  the  oblique  and  direct  her- 
nia differ  from  each  other  in  this  respect  only  in  the  composition 
of  the  fourth  layer,  the  cremaster  occupying  that  place  in  oblique 
hernia,  and  the  conjoined  tendon  in  direct.  If  the  oblique  in- 
guinal hernia  had  reached  no  further  than  the  spermatic  canal, 
then  the  aponeurosis  of  the  external  oblique  muscle  would  take 
the  place  of  the  intercolumnar  fascia.  This  form  of  oblique  in- 
guinal hernia  is  termed  bubonocele. 


ENCYSTED  HERNIA;  THE  HER- 
NIAL SAC  CONTAINING  THE  INTES- 
TINE BEING  BEHIND  THE  TUNICA 

VAGINALIS. — 1.  The  hernial  sac. 
2.  The  cavity  of  the  tunica  vagi- 
nalis.  3.  The  testicle.  4.  The 
spermatic  cord.  The  arrow  shows 
that  three  layers  of  serous  mem- 
brane must  be  divided  before  the 
intestine  can  be  reached. 


DIRECT   INGUINAL   HERNIA. 


51 


The  seat  of  stricture  is  commonly  the  neck  of  the  sac  in  all  the 
varieties  of  inguinal  hernia,  and  the  direction  of  the  incision  for 

Fig.  14. 


A  PORTION  OP  THE  WALL  OP  THE  ABDOMEN  AND  OF  THE  PELVIS  is  HERE 
SKKN  ON  THE  POSTERIOR  ASPECT,  THE  OS  INNOMINATUM  OP  THE  LEFT  SlDE 
WITH  THE  SOFT  PARTS  CONNECTED  WITH  IT  HAVING  BEEN  REMOVED  PROM  THE 
REST  OF  THE  BODY. — 1.  Symphysis  of  pubes.  1'.  Horizontal  branch  of  same. 

2.  Irregular  surface  of  the  ilium  which  has  been  separated  from  the  sacrum. 

3.  Spine  of  ischium.     4.  Tuberosity  of  same.     5.  Obturator  internus.     6.  Rec- 
tus,  covered  with  an  elongation  from     7.  Fascia  transversalis.     8.  Fascia  iliaca 
covering  iliacus  muscle.      9.  Psoas  magnus  cut.     10.  Iliac  artery.     11.  Iliac 
vein.     12.  Epigastric   artery  and  its  two  accompanying  veins.     13.  Vessels  of 
spermatic  cord,  entering  the  abdominal  wall  at  the  internal  ring.     The  ring 
was  in  this  case  of  small  size.     14.  Two  obturator  veins.     15.  The  obliterated 
umbilical  artery.     This  cord,  it  will  be  remembered,  is  not  naturally  in  con- 
tact with  the  abdominal  parietes  in  this  situation. 

its  liberation  should  be  directly  upwards,  by  which  means  any 
danger  to  the  epigastric  artery  is  avoided.  Sometimes  the  stric- 
ture of  oblique  inguinal  hernia  is  occasioned  by  the  lower  border 
of  the  internal  oblique  muscle,  and  sometimes  by  the  external 
abdominal  ring.  In  old  and  large  hernia,  the  internal  ring  is 
dragged  down  so  as  to  become  placed  opposite  the  external,  and 
the  two  together  form  the  neck  of  the  sac.  In  direct  hernia,  the 
fascia  transversalis  with  the  border  of  the  conjoined  tendon  are 
the  structures  forming  the  neck  of  the  sac. 

When  the  layers  of  the  abdominal  parietes  concerned  in  inguinal  her- 
nia have  been  examined,  an  incision  should  be  made  from  the  umbilicus 


52  THE   DISSECTOR. 

to  the  anterior  superior  spine  of  the  ilium  at  each  side,  and  the  triangu- 
lar flap  included  by  these  incisions  turned  down.  On  the  surface  of  this 
flap  will  be  seen  several  prominences  and  depressions  which  require  to 
be  noted. 

In  the  middle  line  behind  the  linea  alba  is  a  prominence  caused 
by  a  fibrous  cord  called  urachus,  which  ascends  from  the  apex  of 
the  bladder  to  the  umbilicus ;  on  either  side  of  the  middle  line, 
and  converging  from  the  sides  of  the  bladder  to  the  urachus  in 
their  course  to  the  umbilicus,  is  another  prominence  caused  by 
a  fibrous  cord  (umbilical  ligament),  the  remains  of  the  hypogas- 
tric  artery  of  the  foetus.  This  cord,  at  its  lower  part,  lies  in 
the  direction  of  the  epigastric  artery,  and  divides  the  lower  part 
of  the  anterior  wall  of  the  abdomen  into  two  fossae,  which  cor- 
respond with  the  seat  of  protrusion  of  the  oblique  and  direct 
inguinal  hernia;  the  former  passing  through  the  outer  fossa,  and 
the  latter  through  the  inner,  between  the  epigastric  artery  and 
the  edge  of  the  rectus. 

CAVITY  OP  THE  ABDOMEN. 

The  cavity  of  the  abdomen  may  now  be  laid  open  by  means  of  an  in- 
cision made  parallel  with,  but  a  little  to  the  left  of,  the  linea  alba  from 
the  ensiform  cartilage  to  the  umbilicus,  and  another  on  each  side  from 
the  umbilicus  to  the  last  rib.  The  flaps  included  by  these  incisions 
should  then  be  turned  back. 

The  cavity  of  the  abdomen  is  bounded  in  front  and  at  the  sides 
by  the  lower  ribs  and  abdominal  muscles ;  behind,  by  the  verte- 
bral column  and  abdominal  muscles ;  above,  by  the  diaphragm ; 
and  below,  by  the  pelvis ;  and  contains  the  alimentary  canal,  the 
organs  subservient  to  digestion,  viz  :  the  liver,  pancreas,  and 
spleen  ;  and  the  organs  of  excretion,  the  kidneys,  with  the  supra- 
renal capsules. 

Regions. — For  convenience  of  description  of  the  viscera,  and 
of  reference  to  the  morbid  affections  of  this  cavity,  the  abdomen 
is  divided  into  certain  districts  or  regions.  Thus,  if  two  trans- 
verse lines  be  carried  around  the  body,  the  one  parallel  with  the 
cartilage  of  the  eighth  rib,  the  other  with  the  highest  point  of 
the  crests  of  the  ilia,  the  abdomen  will  be  divided  into  three 
zones.  Again,  if  a  perpendicular  line  be  drawn,  at  each  side, 
from  the  cartilage  of  the  eighth  rib  to  the  middle  of  Poupart's 
ligament,  the  three  primary  zones  will  each  be  subdivided  into 
three  compartments  or  regions,  a  middle  and  two  lateral. 

The  middle  region  of  the  upper  zone  being  immediately  over 
the  small  end  of  the  stomach,  is  called  epigastric  (frti  yaa-r^p,  over 
the  stomach).  The  two  lateral  regions,  being  under  the  carti- 
lages of  the  ribs,  are  called  hypochondriac  (vx6  %av8poi,  under 
the  cartilages).  The  middle  region  of  the  middle  zone  is  the 


CAVITY   OF   THE   ABDOMEN. 


53 


umbilical;  the  two  lateral,  the  lumbar.     The  middle  region  of 
the  inferior  zone  is  the  hypogastric  (ynb  yaa-eyp,  below  the  sto- 

Fig.  15. 


SURFACE  OF  THE  ABDOMEN,  with  lines  (1,  2,  3,  4)  drawn  upon  it,  marking 
off  its  artificial  subdivisions  into  regions.  5,  5.  Right  and  left  hypochondriac. 
6.  Epigastric  region.  7.  Umbilical.  8,  8.  The  two  lumbar.  9.  Hypogastric. 
10,  10.  The  right  and  left  iliac  regions.  11.  Regio  pubis. 

mach) ;  and  the  two  lateral,  the  iliac.  In  addition  to  these  di- 
visions, we  employ  the  term  inguinal  region  in  reference  to  the 
vicinity  of  Poupart's  ligament. 

Position  of  the  Viscera. — In  the  upper  zone  will  be  seen  the 
liver,  extending  across  from  the  right  to  the  left  side  ;  the  stomach 
and  spleen  on  the  left,  and  the  pancreas  and  duodenum  behind. 
In  the  middle  zone  is  the  transverse  portion  of  the  colon,  with 
the  upper  part  of  the  ascending  and  descending  colon,  omentum, 
small  intestines,  mesentery ;  and  behind,  the  kidneys  and  supra- 
renal capsules.  In  the  inferior  zone  is  the  lower  part  of  the 

5* 


THE   DISSECTOR. 


omentum  and  small  intestines,  the  caecum,  ascending  and  des- 
cending colon,  with  the  sigmoid  flexure,  and  ureters. 

Fig.  16. 


THE  VISCERA  OP  THE  ABDOMEN  IN  SITU.  —  1.  1.  The  flaps  of  the  abdominal 
parietes  turned  aside.  2.  The  liver,  its  left  lobe.  3.  Its  right  lobe.  4.  The 
fundus  of  the  gall-bladder.  5.  The  round  ligament  of  the  liver,  issuing  from 
the  cleft  of  the  longitudinal  fissure,  and  passing  along  the  parietes  of  the  abdo- 
men to  the  umbilicus.  6.  Part  of  the  broad  ligament  of  the  liver.  7.  The 
stomach.  8.  Its  pyloric  end.  9.  The  commencement  of  the  duodenum,  a.  The 
lower  extremity  of  the  spleen,  b,  b.  The  greater  omentum.  c,  c.  The  small 
intestines,  d.  The  caecum,  e.  The  appendix  caeci.  f.  The  ascending  colon. 
g,g.  The  transverse  colon,  h.  The  descending  colon.  *'.  The  sigmoid  flexure 
of  the  colon.  lc.  Appendices  epiploicae  connected  with  the  sigmoid  flexure.  I.  , 
Three  ridges,  representing  the  cords  of  the  urachus  and  the  umbilical  arteries 
ascending  to  the  umbilicus,  m.  Part  of  the  under  surface  of  the  diaphragm. 


The  smooth  and  polished  surface  which  the  viscera  and 
of  the  abdomen  present,  is  due  to  the  peritoneum. 

PERITONEUM.  —  The  peritoneum  (rtfprtsivuv,  to  extend  around) 
is  a  serous  membrane,  and  therefore  a  shut  sac  :  a  single  excep- 
tion exists  in  the  human  subject  to  this  character,  namely,  in  the 
female,  where  the  peritoneum  is  perforated  by  the  open  extremi- 
ties of  the  Fallopian  tubes,  and  is  continuous  with  their  mucous 
lining. 

The  simplest  idea  that  can  be  given  of  a  serous  membrane 


PERITONEUM. 


55 


which  may  apply  equally  to  all,  is,  that  it  invests  the  viscus  or 
viscera,  and  is  then  reflected  upon  the  parietes  of  the  containing 
cavity.  If  the  cavity  contain  only  a  single  viscus,  the  considera- 


THE  REFLECTIONS  OP  THE  PE- 
RITONEUM.— D.  The  diaphragm. 
S.  The  stomach.  C.  The  trans- 
verse colon.  D.  The  transverse 
duodenum.  P.  The  pancreas. 
I.  The  small  intestines.  R.  The 
rectum.  B.  The  urinary  blad- 
der. 1.  The  anterior  layer  of 
the  peritoneum,  lining  the  under 
surface  of  the  diaphragm.  2.  The 
posterior  layer.  3.  The  two  lay- 
ers passing  to  the  posterior  border 
of  the  liver,  and  forming  the  co- 
ronary ligament.  4.  The  lesser 
omentum  ;  the  two  layers  passing 
from  the  under  surface  of  the 
liver  to  the  lesser  curve  of  the 
stomach.  5.  The  two  layers 
meeting  at  the  greater  curve, 
then  passing  downwards  and  re- 
turning upon  themselves,  form- 
ing (6)  the  greater  omentum. 

7.  The    transverse    mesocolon. 

8.  The  posterior  layer  traced  up- 
wards in  front  of  D,  the  transverse 
duodenum,  and  P,  the  pancreas, 
to  become  continuous  with  the 
posterior  layer  (2).    9.  The  fora- 
men of  Winslow  ;  the  dotted  line 
bounding  this  foramen  inferiorly, 
marks  the  course  of  the  hepatic 
artery  forwards,  to  enter  between 
the  layers  of  the  lesser  omentum. 
10.  The  mesentery  encircling  the 
small  intestine.     11.    The  recto- 
vesical  fold,  formed  by  the  de- 
scending   anterior    layer.       12. 
The   anterior    layer   traced   up- 
wards upon  the  internal  surface 

of  the  abdominal  parietes  to  the  layer  (I) 
nienced. 


Fig.  17. 


rith  which  the  examination  com- 


tion  of  the  serous  membrane  is  extremely  simple.  But  in  the 
abdomen,  where  there  are  a  number  of  viscera,  the  serous  mem- 
brane passes  from  one  to  the  other  until  it  has  invested  the  whole, 
before  it  is  reflected  on  the  parietes.  Hence  its  reflections  are  a 
little  more  complicated. 

In  tracing  the  reflections  of  the  peritoneum  in  the  middle  line, 
we  commence  with  the  diaphragm,  which  is  lined  by  two  layers, 
one  from  the  parietes  in  front,  anterior,  and  one  from  the  parietes 
behind,  posterior.  These  two  layers  of  the  same  membrane,  at 
the  posterior  part  of  the  diaphragm,  descend  to  the  upper  surface 


56  THE   DISSECTOR. 

of  the  liver,  forming  the  coronary  and  lateral  ligaments  of  the 
liver.  They  then  surround  the  liver,  one  going  in  front,  the  other 
behind  that  viscus,  and,  meeting  at  its  under  surface,  pass  to  the 
stomach,  forming  the  lesser  omentum.  They  then,  in  the  same 
manner,  surround  the  stomach,  and,  meeting  at  its  lower  border, 
descend  for  some  distance  in  front  of  the  intestines,  and  return  to 
the  transverse  colon,  forming  the  great  omentum  ;  they  then  sur- 
round the  transverse  colon,  and  pass  directly  backwards  to  the 
vertebral  column,  forming  the  transverse  mesocolon.  Here  the 
two  layers  separate  ;  the  posterior  ascends  in  front  of  the  pancreas 
and  aorta,  and  returns  to  the  posterior  part  of  the  diaphragm, 
where  it  becomes  the  posterior  layer  with  which  we  commenced. 
The  anterior  descends,  invests  all  the  small  intestines,  and,  return- 
ing to  the  vertebral  column,  forms  the  mesentery.  It  then  de- 
scends into  the  pelvis  in  front  of  the  rectum,  which  it  holds  in  its 
place  by  means  of  a  fold  called  mesorectum,  forms  a  pouch,  the 
recto-vesical fold,  between  the  rectum  and  bladder,  ascends  upon 
the  posterior  surface  of  the  bladder,  forming  its  false  ligaments, 
and  returns  upon  the  anterior  parietes  of  the  abdomen  to  the 
diaphragm,  whence  we  first  traced  it. 

In  the  female,  after  descending  into  the  pelvis  in  front  of  the 
rectum,  it  is  reflected  upon  the  posterior  surface  of  the  vagina 
and  uterus.  It  then  descends  on  the  anterior  surface  of  the 
uterus,  and  forms  at  either  side  the  broad  ligaments  of  that  organ. 
From  the  uterus  it  ascends  upon  the  posterior  surface  of  the 
bladder  and  anterior  parietes  of  the  abdomen,  and  is  continued, 
as  in  the  male,  to  the  diaphragm. 

In  this  way  the  continuity  of  the  peritoneum,  as  a  whole,  is 
distinctly  shown,  and  it  matters  not  where  the  examination  com- 
mences or  where  it  terminates,  still  the  same  continuity  of  surface 
will  be  discernible  throughout.  If  we  trace  it  from  side  to  side 
of  the  abdomen,  we  may  commence  at  the  umbilicus ;  we  then 
follow  it  outwards,  lining  the  inner  side  of  the  parietes,  to  the 
ascending  colon ;  it  surrounds  that  intestine :  it  then  surrounds 
the  small  intestine,  and,  returning  on  itself,  forms  the  mesentery. 
It  then  invests  the  descending  colon,  and  reaches  the  parietes  on 
the  opposite  side  of  the  abdomen,  whence  it  may  be  traced  to  the 
exact  point  from  which  we  started. 

The  viscera  which  are  thus  shown  to  be  invested  by  the  peri- 
toneum in  its  course  downwards  are  the  — 

Liver,  Small  intestines, 

Stomach,  Pelvic  viscera. 

Transverse  colon, 

The  folds,  formed  between  these  and  between  the  diaphragm 
and  the  liver,  are — 


PERITONEUM.  5f 

(Diaphragm.) 
Broad,  coronary,  and  lateral  ligaments. 

(Liver.) 
Lesser  or  gastro-hepatic  omentum. 

(Stomach.) 
Greater  or  gastro-colic  omentum. 

(Transverse  colon.) 
Transverse  mesocolon. 
Mesentery, 
Meso-rectum, 
Recto-vesical  fold, 
False  ligaments  of  the  bladder. 
And  in  the  female,  the  — 

Broad  ligaments  of  the  uterus. 

The  ligaments  of  the  liver  will  be  described  with  that  organ. 
The  lesser  omentum  (gastro-hepatic)  is  the  duplicature  which 
passes  between  the  liver  and  the  upper  border  of  the  stomach. 
It  is  extremely  thin,  excepting  at  its  right  border,  where  it  is 
free,  and  contains  between  its  layers  the  — 
Hepatic  artery, 

Ductus  communis  choledochus, 
Lymphatics, 
Portal  vein, 

Hepatic  plexus  of  nerves. 

These  structures  are  inclosed  in  a  loose  cellular  tissue,  called 
Glisson's1  capsule.  The  relative  position  of  the  three  vessels  is, 
the  artery  to  the  left,  the  duct  to  the  right,  and  the  vein  between 
and  behind. 

If  the  finger  be  introduced  behind  this  right  border  of  the  lesser 
omentum,  it  will  be  situated  in  an  opening  called  the  foramen  of 
Window*  In  front  of  the  finger  will  lie  the  right  border  of  the 
lesser  omentum ;  behind  it  the  diaphragm,  covered  by  the  as- 
cending or  posterior  layer  of  the  peritoneum  ;  belotc,  the  hepatic 
artery,  curving  forwards  from  the  creliac  axis ;  and  above,  the 
lobus  Spigelii.  These,  therefore,  are  the  boundaries  of  the 
foramen  of  Winslow,  which  is  nothing  more  than  a  constriction 
of  the  general  cavity  of  the  peritoneum  at  this  point,  arising  out 

1  Francis  Glisson,  Professor  of  Medicine  in  the  University  of  Cam- 
bridge.    His  work,  "  De  Anatomia  Hepatis,"  was  published  in  1654. 

2  Jacob  Benignus  Winslow.    His  "  Exposition  Anatomique  de  la  Struc- 
ture du  Corps  Humain"  was  published  in  Paris  in  1732. 


58  THE   DISSECTOR. 

of  the  necessity  for  the  hepatic  and  gastric  arteries  to  pass  for- 
wards from  the  cceliac  axis  to  reach  their  respective  viscera. 

If  air  be  blown  through  the  foramen  of  Winslow,  it  will  de- 
scend behind  the  lesser  omentum  and  stomach  to  the  space 
between  the  descending  and  ascending  pair  of  layers,  forming 
the  great  omentum.  This  is  sometimes  called  the  lesser  cavity 
of  the  peritoneum,  and  that  external  to  the  foramen  the  greater 
cavity ;  in  which  case  the  foramen  is  considered  as  the  means  of 
communication  between  the  two.  There  is  a  great  objection  to 
this  division,  as  it  might  lead  the  inexperienced  to  believe  that 
there  were  really  two  cavities.  There  is  but  one  only,  the  fora- 
men of  Winslow  being  merely  a  constriction  of  that  one,  to 
facilitate  the  communication  between  the  nutrient  arteries  and 
the  viscera  of  the  upper  part  of  the  abdomen. 

The  great  omentum  (gastro-colic)  consists  of  four  layers  of 
peritoneum,  the  two  which  descend  from  the  stomach,  and  the 
same  two,  returning  upon  themselves  to  the  transverse  colon. 
A  quantity  of  adipose  substance  is  deposited  around  the  vessels 
which  ramify  through  its  structure.  It  would  appear  to  perform 
a  double  function  in  the  economy :  1st.  Protecting  the  intes- 
tines from  cold ;  and,  2dly.  Facilitating  the  movement  of  the  in- 
testines upon  each  other  during  their  vermicular  action. 

The  transverse  mesocolon  (ftt'coj,  middle,  being  attached  to 
the  middle  of  the  cylinder  of  the  intestine)  is  the  medium  of  con- 
nection between  the  transverse  colon  and  the  posterior  wall  of 
the  abdomen.  It  affords  to  the  nutrient  arteries  a  passage  to 
reach  the  intestine,  and  incloses  between  its  layers,  at  the  pos- 
terior part,  the  transverse  portion  of  the  duodenum.  It  also 
forms  a  transverse  septum  across  the  abdominal  cavity. 

The  mesentery  (piaov  I*f  «p<w,  being  connected  to  the  middle  of 
the  cylinder  of  the  small  intestine)  is  the  medium  of  connection 
between  the  small  intestines  and  the  posterior  wall  of  the  abdo- 
men. It  is  oblique  in  its  direction,  being  attached  to  the  pos- 
terior wall,  from  the  left  nide  of  the  second  lumbar  vertebra  to 
the  right  iliac  fossa.  It  retains  the  small  intestines  in  their  places, 
and  gives  passage  to  the  mesenteric  arteries,  veins,  nerves,  and 
lymphatics. 

The  mesorectum,  in  like  manner,  retains  the  rectum  in  connec- 
tion with  the  front  of  the  sacrum.  Besides  this,  there  are  some 
minor  folds  in  the  pelvis,  as  the  recto-vesical  fold,  the  false  liga- 
ments of  the  bladder,  and  the  broad  ligaments  of  the  uterus. 

The  appendices  epiploicce  are  small  irregular  pouches  of  the 
peritoneum,  filled  with  fat,  and  situated  like  fringes  upon  the 
large  intestine. 

Three  other  duplicatures  of  the  peritoneum  are  situated  in  the 
sides  of  the  abdomen;  they  are,  the  gastro-phrenic  ligament,  the 


ALIMENTARY  CANAL — THE   STOMACH.  59 

gastro-splenic  omentum,  the  ascending  and  descending  meso- 
colon.  The  gastro-phrenic  ligament  is  a  small  duplicature  of  the 
peritoneum,  which  descends  from  the  diaphragm  to  the  extremity 
of  the  oesophagus  and  lesser  curve  of  the  stomach.  The  gastro- 
splenic  omentum  is  the  duplicature  which  connects  the  spleen  to 
the  stomach.  The  ascending  mesocolon  is  the  fold  which  connects 
the  upper  part  of  the  ascending  colon  with  the  posterior  wall  of 
the  abdomen ;  and  the  descending  mesocolon,  that  which  retains 
the  sigmoid  flexure  in  connection  with  the  abdominal  wall. 

ALIMENTARY  CANAL. 

The  alimentary  canal  is  a  musculo-membranous  tube,  extending 
from  the  mouth  to  the  anus.  It  is  variously  named  in  the  dif- 
ferent parts  of  its  course,  as,  for  example,  in  its  upper  part, 
mouth,  pharynx,  oesophagus ;  the  remaining  part  is  situated  within 
the  abdomen,  and  consists  of  the  stomach,  the  small  intestine,  and 
large  intestine.  The  small  intestine  is  subdivided  into  three 
portions,  duodenum,  jejunum,  and  ileum ;  and  the  large  intestine 
also  into  three,  ca3cum,  colon,  and  rectum. 

THE  STOMACH. 

The  stomach  is  an  expansion  of  the  alimentary  canal,  situated 
in  the  left  hypochondriac  and  epigastric  region,  and,  for  a  small 
extent,  in  the  right  hypochondriac  region.  It  is  directed  some- 
what obliquely  from  above  downwards,  from  left  to  right,  and 
from  behind  forwards;  and  in  the  female,  where  the  injurious 
system  of  tight-lacing  has  been  pursued,  is  longer  than  in  the 
male.  On  account  of  the  peculiarity  of  its  form,  it  is  divided 
into  a  greater  or  splenic,  and  a  lesser  or  pyloric,  end;  a  lesser 
curvature  above,  and  a  greater  curvature  below  ;  an  anterior  and 
a  posterior  surface;  a  cardiac  orifice,  and  a  pyloric  orifice.  The 
great  end  (fundus)  is  not  only  of  large  size,  but  expands  beyond 
the  point  of  entrance  of  the  oesophagus,  and  is  embraced  by  the 
concave  surface  of  the  spleen.  The  pylorus  is  the  small  and 
contracted  extremity  of  the  organ ;  it  is  situated  on  a  plane 
anterior  and  inferior  to  the  cardiac  orifice,  and  lies  in  contact 
with  the  under  surface  of  the  liver,  often  reaching  to  the  gall- 
bladder. Near  the  lesser  end  of  the  stomach  is  a  small  dilatation, 
called  by  Willis  the  antrum  of  the  pylorus.  The  two  curvatures 
give  attachment  to  the  peritoneum  ;  the  upper  curve  to  the  lesser 
omentum,  and  the  lower  to  the  greater  oraentum.  The  anterior 
surface  looks  upwards  and  forwards,  and  is  in  relation  with  the 
diaphragm  (which  separates  it  from  the  viscera  of  the  thorax, 
and  from  the  six  lower  ribs),  with  the  left  lobe  of  the  liver;  and, 
in  the  epigastric  region,  with  the  abdominal  parietes.  The  pos- 


60  THE   DISSECTOR. 

terior  surface  looks  downwards  and  backwards,  and  is  in  relation 
with  the  diaphragm,  the  pancreas,  the  third  portion  of  the  duo- 
denum, the  transverse  mesocolon,  the  left  kidney,  and  left  supra- 
renal capsule;  this  surface  forms  the  anterior  boundary  of  that 

Fig.  18. 


A  VERTICAL  AND  LONGITUDINAL  SECTION  OP  THE  STOMACH  AND  DUODENUM, 

MADE     IN     SUCH    A     DIRECTION    AS     TO     INCLUDE     THE     TWO     ORIFICES     OF     THE 

STOMACH. — 1.  The  oesophagus ;  upon  its  internal  surface  the  plicated  arrange- 
ment of  the  cuticular  epithelium  is  shown.  2.  The  cardiac  orifice  of  the  stomach, 
around  which  the  fringed  border  of  the  cuticular  epithelium  is  seen.  3.  The 

treat  end  of  the  stomach.  4.  Its  lesser  or  pyloric  end.  5.  The  lesser  curve. 
.  The  greater  curve.  7.  The  dilatation  at  the  lesser  end  of  the  stomach  which 
received  from  Willis  the  name  of  antrum  of  the  pylorus.  This  may  be  regarded 
as  the  rudiment  of  a  second  stomach.  8.  The  rugae  of  the  stomach  formed  by 
the  mucous  membrane  :  their  longitudinal  direction  is  shown.  9.  The  pylorus. 
10.  The  oblique  portion  of  the  duodenum.  11.  The  descending  portion.  12. 
The  pancreatic  duct,  and  the  ductus  communis  choledochus  close  to  their  ter- 
mination. 13.  The  papilla  upon  which  the  ducts  open.  14.  The  transverse 
portion  of  the  duodenum.  15.  The  commencement  of  the  jejunum.  In  the  in- 
terior of  the  duodenum  and  jejunum,  the  valvulae  conniventes  are  seen. 

cul-de-sac  of  the  peritoneum  which  is  situated  behind  the  lesser 
omentum,  and  extends  into  the  greater  omentum.  In  a  state  of 
distension,  as  after  a  meal,  the  anterior  surface  becomes  superior, 
and  the  greater  curvature  is  directed  forwards  against  the  abdo- 
minal parietes. 

SMALL  INTESTINES. 

The  small  intestine  is  about  twenty  or  twenty-five  feet  in 
length,  and  is  divisible  into  three  portions,  duodenum,  jejunum, 
and  ileum. 

The  duodenum  (called  8^8£xa.8dxtv^.ov  by  Herophilus)  is  some- 


SMALL  INTESTINES.  61 

what  larger  than  the  rest  of  the  small  intestines,  and  has  received 
its  name  from  being  about  equal  in  length  to  the  breadth  of 
twelve  fingers  (eight  or  ten  inches).  Commencing  at  the 
pylorus,  it  ascends  obliquely  backwards  to  the  under  surface  of 
the  liver;  it  next  descends  perpendicularly  in  front  of  the  right 
kidney,  and  then  passes  nearly  transversely  across  the  third  lum- 
bar vertebra;  terminating  in  the  jejunum  on  the  left  side  of  the 
second  lumbar  vertebra,  where  it  is  crossed  by  the  superior  me- 
senteric  artery  and  vein.  The  first  or  oblique  portion  of  its 
course,  between  two  and  three  inches  in  length,  is  completely 
inclosed  by  the  peritoneum;  it  is  in  relation,  above,  with  the 
liver  and  neck  of  the  gall-bladder;  in  front,  with  the  great 
omentum  and  abdominal  parietes;  and  behind,  with  the  right 
border  of  the  lesser  omentum  and  its  vessels.  The  second  or 
perpendicular  portion  is  situated  altogether  behind  the  peri- 
toneum; it  is  in  relation,  by  its  anterior  surface,  with  the  com- 
mencement of  the  arch  of  the  colon ;  by  its  posterior  surface,  with 
the  concave  margin  of  the  right  kidney,  the  inferior  vena  cava, 
and  ductus  communis  choledochus ;  by  its  right  border,  with  the 
ascending  colon;  and  by  its  left  border,  with  the  pancreas.  The 
ductus  communis  choledochus  and  pancreatic  duct  open  into  the 
internal  and  posterior  side  of  the  perpendicular  portion,  a  little 
below  its  middle.  The  third  or  transverse  portion  of  the  duo- 
denum lies  between  the  diverging  layers  of  the  transverse  meso- 
colon,  with  which  and  with  the  stomach  it  is  in  relation  in  front; 
above,  it  is  in  contact  with  the  lower  border  of  the  pancreas,  the 
superior  mesenteric  artery  and  vein  being  interposed;  and,  behind, 
it  rests  upon  the  inferior  vena  cava  and  aorta. 

The  jejunum  (jejunus,  empty)  is  named  from  being  generally 
found  empty.  It  forms  the  upper  two-fifths  of  the  small  intes- 
tine ;  commencing  at  the  duodenum  on  the  left  side  of  the  second 
lumbar  vertebra,  and  terminating  in  the  ileum.  It  is  thicker  to 
the  touch  than  the  rest  of  the  intestine,  and  has  a  pinkish  tinge 
from  containing  more  mucous  membrane  than  the  ileum. 

The  ileum  («Xftv,  to  twist,  to  convolute)  includes  the  remain- 
ing three-fifths  of  the  small  intestine.  It  is  somewhat  smaller  in 
calibre,  thinner  in  texture,  and  paler  than  the  jejunum ;  but  there 
is  no  mark  by  which  to  distinguish  the  termination  of  the  one, 
or  the  commencement  of  the  other.  It  terminates  in  the  right 
iliac  fossa,  by  opening  at  an  obtuse  angle  into  the  colon. 

The  jejunum  and  ileum  are  surrounded,  above  and  at  the  sides, 
by  the  colon;  in  front,  they  are  in  relation  with  the  omentum 
and  abdominal  parietes;  they  are  retained  in  their  position  by 
the  mesentery,  which  connects  them  with  the  posterior  wall  of 
the  abdomen ;  and  below  they  descend  into  the  cavity  of  the 
6 


62  THE   DISSECTOR. 

pelvis.  At  about  the  lower  third  of  the  ileum  a  pouch-like  pro- 
cess or  diverticulum  of  the  intestine  is  occasionally  seen.  This 
is  a  vestige  of  embryonic  structure,  and  is  formed  by  the  oblite- 
ration of  the  vitelline  duct  at  a  short  distance  from  the  cylinder 
of  the  intestine. 

LARGE  INTESTINE. 

The  large  intestine,  about  five  feet  in  length,  is  sacculated  in 
appearance,  and  is  divided  into  the  ccecum,  colon,  and  rectum. 

The  ccecum  (caecus,  blind)  is  the  blind  pouch,  or  cul-de-sac,  at 
the  commencement  of  the  large  intestine.  It  is  situated  in  the 
right  iliac  fossa,  and  is  retained  in  its  place  by  the  peritoneum 
which  passes  over  its  anterior  surface;  its  posterior  surface  is 
connected  by  loose  cellular  tissue  with  the  iliac  fascia.  Attached 
to  its  extremity  is  the  appendix  vermiformis,  a  long  worm-shaped 
tube,  the  rudiment  of  the  lengthened  caecum  found  in  all  mam- 
miferous  animals  except  man  and  the  higher  quadrumana.  The 
appendix  varies  in  length  from  one  to  five  or  six  inches;  it  is 
about  equal  in  diameter  to  a  goose-quill,  and  is  connected  with 
the  posterior  and  left  aspect  of  the  caecum,  near  the  extremity  of 
the  ileum.  It  is  usually  more  or  less  coiled  upon  itself,  and  re- 
tained in  that  coil  by  a  falciform  duplicature  of  peritoneum.  Its 
canal  is  extremely  small,  and  the  orifice  by  which  it  opens  into 
the  caecum  not  unfrequently  provided  with  an  incomplete  valve. 
Occasionally  the  peritoneum  invests  the  caecum  so  completely  as 
to  constitute  a  mesocaecum,  which  permits  of  an  unusual  degree 
of  movement  in  this  portion  of  the  intestine,  and  serves  to  ex- 
plain the  occurrence  of  hernia  of  the  caecum  upon  the  right  side. 
The  caecum  is  the  most  dilated  portion  of  the  large  intestines. 

The  colon  is  divided  into  ascending,  transverse,  and  descending. 
The  ascending  colon  passes  upwards  from  the  right  iliac  fossa, 
through  the  right  lumbar  region,  to  the  under  surface  of  the 
liver.  It  then  bends  inwards  (hepatic  flexure),  and  crosses  the 
upper  part  of  the  umbilical  region,  under  the  name  of  transverse 
colon;  and,  on  the  left  side  (splenic  flexure),  descends  (descending 
colon)  through  the  left  lumbar  region  to  the  left  iliac  fossa, 
where  it  makes  a  remarkable  curve  upon  itself,  which  is  called 
the  sigmoid flexure. 

The  ascending  colon,  the  most  dilated  portion  of  the  large  in- 
testine, next  to  the  caecum,  is  retained  in  its  position  in  the 
abdomen  either  .by  the  peritoneum  passing  simply  in  front  of  it, 
or  by  a  narrow  mesocolon.  It  is  in  relation,  in  front,  with  the 
small  intestine  and  abdominal  parietes;  behind,  with  the  quad- 
ratus  lumborum  muscle  and  right  kidney;  internally,  with  the 
small  intestine  and  the  perpendicular  portion  of  the  duodenum ; 


LARGE   INTESTINE.  63 

and,  by  its  upper  extremity,  with  the  under  surface  of  the  liver 
and  gall-bladder.  The  transverse  colon,  the  longest  portion  of 
the  large  intestine,  forms  a  curve  across  the  cavity  of  the  abdo- 
men, the  convexity  of  which  looks  forwards  and  sometimes  down- 
wards. It  is  in  relation,  by  its  upper  surface,  with  the  liver, 
gall-bladder,  stomach,  and  lower  extremity  of  the  spleen  ;  by  its 
lower  surface,  with  the  small  intestine ;  by  its  anterior  surface, 
with  the  anterior  layers  of  the  great  omentum  and  the  abdominal 
parietes;  and,  by  its  posterior  surface,  with  the  transverse  meso- 
colon.  The  descending  colon  is  smaller  in  calibre,  and  is  situated 
more  deeply  than  the  ascending  colon :  its  relations  are  precisely 
similar.  The  sigmoid flexure  is  the  narrowest  part  of  the  colon; 
it  curves  in  the  first  place  upwards  and  then  downwards,  and  to 
one  or  the  other  side,  and  is  retained  in  its  place  by  a  mesocolon. 
It  is  in  relation,  in  front,  with  the  small  intestine  and  abdominal 
parietes;  behind,  with  the  iliac  fossa;  and,  on  either  side,  with 
the  small  intestine. 

The  rectum,  the  termination  of  the  large  intestine,  is  seven  or 
eight  inches  in  length.  It  has  received  its  name,  not  so  much 
from  the  direction  of  its  course,  as  from  the  straightness  of  its 
form  in  comparison  with  the  colon.  It  descends,  from  opposite 
the  left  sacro-iliac  symphysis,  in  front  of  the  sacrum,  forming  a 
gentle  curve  to  the  right  side,  and  then  returning  to  the  middle 
line ;  opposite  the  extremity  of  the  coccyx  it  curves  backwards 
to  terminate  at  the  anus  at  about  an  inch  in  front  of  the  apex  of 
that  bone.  The  rectum,  therefore,  forms  a  double  flexure  in  its 
course,  the  one  being  directed  from  side  to  side,  the  other  from 
before  backwards.  It  is  smaller  in  calibre  at  its  upper  part  than 
the  sigmoid  flexure,  but  becomes  gradually  larger  as  it  descends, 
and  at  its  lower  extremity,  previously  to  its  termination  at  the 
anus,  forms  a  dilatation  of  considerable  but  variable  magni- 
tude. 

With  reference  to  its  relations,  the  rectum  is  divided  into 
three  portions ;  the  first,  including  half  its  length,  extends  to 
about  the  middle  of  the  sacrum,  is  completely  surrounded  by 
peritoneum,  and  connected  to  the  sacrum  by  means  of  the  meso- 
rectum.  It  is  in  relation,  above,  with  the  left  sacro-iliac  sym- 
physis ;  and,  below,  with  the  branches  of  the  internal  iliac  artery, 
sacral  plexus  of  nerves,  and  left  ureter;  one  or  two  convolutions 
of  the  small  intestine  are  interposed  between  the  front  of  the 
rectum  and  the  bladder,  in  the  male;  and  between  the  rectum 
and  the  uterus  with  its  appendages  in  the  female.  The  second 
portion,  about  three  inches  in  length,  is  closely  attached  to  the 
surface  of  the  sacrum,  and  covered  by  peritoneum  only  in  front; 
it  is  in  relation  by  its  lower  part  with  the  base  of  the  bladder, 
vesicuhe  seminales,  and  prostate  gland,  and  in  the  female  with 


64 


THE   DISSECTOR. 


Fig.  19. 


the  vagina.  The  third  portion  curves  backwards  from  opposite 
the  prostate  gland  and  tip  of  the  coccyx,  to  terminate  at  the 
anus;  it  is  embraced  by  the  levatores  ani,  and  is  about  one  inch 
and  a  half  in  length.  It  is  separated  from  the  membranous  por- 
tion of  the  urethra  by  a  triangular  space ;  in  the  female,  this 

space  intervenes  between 
the  vagina  and  the  rec- 
tum, and  constitutes  by 
its  base  the  perineum. 

The  anus  is  situated 
at  a  little  more  than  an 
inch  in  front  of  the  ex- 
tremity, of  the  coccyx. 
The  integument  around 
it  is  covered  with  hairs, 
and  is  thrown  into  nu- 
merous radiated  plaits, 
which  are  obliterated 
during  the  passage  of 
feces.  The  margin  of 
the  anus  is  provided 
with  an  abundance  of 
sebaceous  glands,  and 
the  epiderma  may  be 
seen  terminating  by  a 
fringed  and  scalloped 
border  at  a  few  lines 
above  the  extremity  of 
the  opening. 

Structure. — The  aliment- 
ary canal  within  the  abdo- 
men possesses  four  coats  ; 
serous,  muscular,  cellular, 
and  mucous. 

The  serous  coat  is  derived 
from  the  peritoneum.  The 
stomach  is  completely  sur- 
rounded by  peritoneum,  ex^" 
cepting  along  the  line  of 
attachment  of  the  great  and 
lesser  omentum.  The  first 
or  oblique  portion  of  the  duo- 
denum is  also  completely  in- 
cluded by  the  serous  mera- 

DlAGRAM   OF    THE    STOMACH    AND    INTESTINES,    TO    SHOW    THEIR    COURSE. — 

1.  Stomach.  2.  (Esophagus.  3.  Left,  and  4.  Right  end  of  the  stomach 
5.  6.  Duodenum.  7.  Convolutions  of  jejunum.  8.  Those  of  ileum.  9.  Cae- 
cum. 10.  Vermiform  appendix.  11.  Ascending.  12.  Transverse  ;  and  13.  De- 
scending colon.  14.  Commencement  of  sigmoid  flexure.  15.  Rectum. 


STRUCTURE   OP   THE  INTESTINES.  65 

brane,  with  the  exception  of  the  points  of  attachment  of  the  omenta.  The 
descending  portion  has  merely  a  partial  covering  on  its  anterior  surface. 
The  transverse  portion  is  also  behind  the  peritoneum,  being  situated  between 
the  two  layers  of  the  transverse  mesocolon,  and  has  but  a  partial  cover- 
ing. The  rest  of  the  small  intestine  is  completely  invested  by  it,  excepting 
along  the  concave  border  to  which  the  mesentery  is  attached.  The 
caecum  is  more  or  less  invested  by  the  peritoneum,  the  more  frequent 
disposition  being  that  in  which  the  intestine  is  surrounded  for  three- 
fourths  only  of  its  circumference.  The  ascending  and  the  descending 
colon  are  covered  by  the  serous  membrane  only  in  front.  The  transverse 
colon  is  invested  completely,  with  the  exception  of  the  lines  of  attach- 
ment of  the  greater  omentum  and  transverse  mesocolon.  And  the  sig- 
moid  flexure  is  entirely  surrounded,  with  the  exception  of  the  part  corre- 
sponding with  the  junction  of  the  left  mesocolon.  The  upper  third  of 
the  rectum  is  completely  inclosed  by  the  peritoneum ;  the  middle  third 
has  an  anterior  covering  only,  and  the  inferior  third  none  whatsoever. 

The  muscular  coat  is  composed  of  two  planes  of  fibres,  an  external  lon- 
gitudinal and  an  internal  circular. 

On  the  stomach,  the  longitudinal  fibres  are  most  apparent  along  the 
lesser  curve,  and  the  circular  at  the  smaller  end.  At  the  pylorus  the 
latter  are  aggregated  into  a  thick  circular  ring,  which,  with  the  spiral 
fold  of  mucous  membrane  found  in  this  situation,  constitutes  the  pyloric 
valve.  At  the  great  end  of  the  stomach  a  new  order  of  fibres  is  intro- 
duced, having  for  their  object  to  strengthen  and  compress  that  extremity 
of  the  organ.  They  are  directed  more  or  less  horizontally  from  the  great 
end  towards  the  lesser  end,  and  are  generally  lost  upon  the  sides  of  the 
stomach  at  about  its  middle;  these  are  the  oblique  fibres.  They  are 
most  numerous  at  the  upper  part  of  the  cul-de-sac,  near  the  cardiac 
orifice. 

The  small  intestine  is  provided  with  both  layers  of  fibres,  pretty  equally 
distributed  over  the  entire  surface  ;  the  longitudinal  fibres  being  best 
marked  along  the  free  border.  At  the  termination  of  the  ileum  the  cir- 
cular fibres  are  continued  into  the  two  folds  of  the  ileo-caecal  valve, 
while  the  longitudinal  fibres  pass  onwards  to  the  large  intestine.  In  the 
large  intestine,  the  longitudinal  fibres  commence  at  the  appendix  vermi- 
forruis,  and  are  collected  into  three  bands,  an  anterior,  broad,  and  two 
posterior  and  narrower  bands.  These  bands  are  nearly  one-half  shorter 
than  the  intestine,  and  serve  to  maintain  the  sacculated  structure  which 
is  characteristic  of  the  caecum  and  colon.  In  the  descending  colon,  the 
posterior  bands  usually  unite  and  form  a  single  band.  From  this  point 
the  bands  are  continued  downwards  upon  the  sigmoid  flexure  to  the  rec- 
tum, around  which  they  spread  out  and  form  a  thick  and  very  muscular 
longitudinal  layer.  The  circular  fibres  in  the  caecum  and  colon  are  ex- 
ceedingly thin ;  in  the  rectum  they  are  thicker,  and  near  its  lower 
extremity  they  are  aggregated  into  the  thick  muscular  band  which  is 
known  as  the  internal  sphincter  ani.  Between  the  latter  and  the  mu- 
cous membrane  are  several  narrow  fasciculi  of  longitudinal  muscular 
fibres,  somewhat  more  than  an  inch  in  length,  which  have  been  described 
by  Horner,  of  Philadelphia. 

The  cellular  coat  (submuoous,  nervous)  is  a  moderately  thick  stratum 
of  fibro-cellular  tissue  which  serves  as  the  bond  of  connection  between 
the  muscular  and  mucous  coat.  It  gives  support  to  the  mucous  mem- 
brane, and  affords  a  nidus  to  the  vessels  and  nerves  previously  to  their 
distribution  to  that  membrane.  It  is  firmly  adherent  to  the  mucous 
layer,  but  more  loosely  to  the  muscular  coat. 

6* 


66  THE   DISSECTOR. 

The  mucous  coat  in  the  stomach,  is  thin  at  the  great  extremity,  and 
thicker  towards  the  pyloric  extremity.  It  is  of  a  pinkish  color,  the  depth 
of  color  being  greater  in  infancy  than  in  the  adult,  and  less  in  old  age  ; 
and  being  increased  under  the  excitement  of  digestion.  It  is,  moreover, 
formed  into  plaits  or  rugce,  which  are  disposed  for  the  most  part  in  a  lon- 
gitudinal direction.  The  rugae  are  most  numerous  towards  the  lesser 
end  of  the  stomach;  while  around  the  cardiac  orifice  they  assume  a 
radiated  arrangement.  At  the  pylorus  the  mucous  membrane  forms  a 
circular  or  spiral  fold  which  constitutes  a  part  of  the  apparatus  of  the 
pyloric  valve.  In  the  lower  half  of  the  duodenum,  the  whole  length  of 
the  jejunum,  and  the  upper  part  of  the  ileum,  it  forms  valvular  folds 
called  valvular  conniventes,  which  are  several  lines  in  breadth  in  the  lower 
part  of  the  duodenum  and  upper  portion  of  the  jejunum,  and  diminish 
gradually  in  size  towards  each  extremity.  These  folds  do  not  entirely 
surround  the  cylinder  of  the  intestine,  but  extend  for  about  one  half  or 
three-fourths  of  its  circumference.  In  the  lower  half  of  the  ileum  the 
mucous  lining  is  without  folds ;  hence  the  thinness  of  the  coats  of  this 
intestine  as  compared  with  the  jejunum  and  duodenum.  At  the  termi- 
nation of  the  ileum  in  the  caecum,  the  mucous  membrane  forms  two 
folds,  which  are  strengthened  by  the  muscular  coat,  and  project  into  the 
caecum.  These  are  the  ileo-ccBcal  valve  (valvula  Bauhini).  In  the  cae- 
cum and  colon  the  mucous  membrane  is  raised  into  crescentic  folds, 
which  correspond  with  the  sharp  edges  of  the  sacculi ;  and,  in  the  rec- 
tum, it  forms  three  valvular  folds,1  one  of  which  is  situated  near  the 
commencement  of  the  intestine ;  the  second,  extending  from  the  side  of 
the  tube,  is  placed  opposite  the  middle  of  the  sacrum ;  and  the  third, 
which  is  the  largest  and  most  constant,  projects  from  the  anterior  wall 
of  the  intestine  opposite  the  base  of  the  bladder.  Besides  these  folds,  the 
membrane  in  the  empty  state  of  the  intestine  is  thrown  into  longitudinal 
plaits,  somewhat  similar  to  those  of  the  oesophagus ;  these  have  been 
named  the  columns  of  the  rectum.  The  mucous  membrane  of  the  rectum 
is  connected  to  the  muscular  coat  by  a  very  loose  cellular  tissue,  as  in 
the  oesophagus. 

Structure  of  Mucous  Membrane. — Mucous  membrane  is  analogous  to  the 
cutaneous  covering  of  the  exterior  of  the  body,  and  resembles  that  tissue 
very  closely  in  its  structure.  It  is  composed  of  two  layers,  epithelium 
and  corium. 

The  epithelium  is  the  epiderma  of  the  mucous  membrane.  Throughout 
the  pharynx  and  oesophagus  it  resembles  the  epiderma,  both  in  appear- 
ance and  character.  It  is  continuous  with  the  epiderma  of  the  skin  at 
the  margin  of  the  lips,  and  terminates  by  an  irregular  border  at  the 
cardiac  orifice  of  the  stomach.  At  the  opposite  extremity  of  the  canal  it 
terminates  by  a  scalloped  border  just  within  .the  verge  of  the  anus.  In 
the  mouth  it  is  composed  of  laminae  of  cytoblasts,  cells,  and  polyhedral 
scales.  Each  cell  and  each  scale  possesses  a  central  nucleus,  and  within 
the  nucleus  are  one  or  more  nucleus-corpuscles.  According  to  Mr. 
Nasmyth,2  the  deepest  lamina  of  the  epithelium  appears  to  consist  of 


1  Mr.  Houston,  ('  On  the  Mucous  Membrane  of  the  Rectum."    Dublin 
Hospital  Reports,  vol.  v. 

2  "Investigations  into  the  Structure  of  the  Epithelium,"  presented  to 
the  medical  section  of  the  British  Medical  Association,  in  1839,  published 
in  a  work  entitled  "  Three  Memoirs  ou  the  Development  of  the  Teeth  and 
Epithelium,"  }841. 


STRUCTURE   OF   THE   INTESTINES.  67 

nuclei  (cytoblasts)  only ;  in  the  next,  the  investing  vesicle  or  cell  is  deve- 
loped ;  the  cells  by  degrees  enlarge  and  become  flattened,  and  in  the 
superficial  laminae  are  converted  into  thin  scales.  The  nuclei,  the  cells, 
and  the  scales  are  connected  together  by  a  glutinous  fluid  of  the  consist- 
ence of  jelly,  which  contains  an  abundance  of  minute  opaque  granules. 
The  scales  of  the  superficial  layer  overlap  each  other  by  their  margins. 
During  the  natural  functions  of  the  mucous  membrane  the  superficial 
scales  exfoliate  continually  and  give  place  to  the  deeper  layers.  In  ihe 
upper  part  of  the  pharynx  near  the  posterior  nares,  and  around  the 
apertures  of  the  Eustachian  tubes,  the  epithelium  is  cilated ;  in  the 
pharynx  and  oesophagus  it  is  squamous,  and  in  the  latter  remarkable  for 
its  thickness.  In  the  stomach  and  intestines  the  epithelial  bodies  are 
pyriform  in  shape,  and  have  a  columnar  arrangement,  the  apices  being 
applied  to  the  papillary  surface  of  the  membrane",  and  the  bases  forming, 
by  their  approximation,  the  free  intestinal  surface.  Each  column  is 
provided  with  a  central  nucleus  and  nucleus-corpuscle,  which  gives  its 
middle  a  swollen  appearance  ;  and,  from  the  transparency  of  its  structure, 
the  nucleus  may  be  seen  through  the  base  of  the  column,  when  examined 
from  the  surface.  Around  the  circular  villi,  the  columns,  from  being 
placed  perpendicularly  to  the  surface,  have  a  radiated  arrangement.  The 
columnar  epithelium  is  produced,  in  the  same  manner  with  the  lami- 
nated epithelium,  in  cytoblasts,  cells,  and  columns,  and  the  latter  are 
continually  thrown  off  to  give  place  to  successive  layers. 

The  corium  is  analogous  to  the  corium  of  the  skin,  and,  like  it,  is  the 
formative  structure  by  which  the  epithelium  is  produced.  Its  surface 
presents  several  varieties  of  appearance  when  examined  in  different  parts 
of  its  extent.  In  the  stomach  it  forms  minute  polyhedral  cells  (alveoli), 
into  the  floor  of  which  the  gastric  follicles  open,  and  upon  their  margins 
at  the  pyloric  end  of  the  stomach  are  numerous  small  flat  villi.  In  the 
small  intestine  it  presents  numerous  minute,  projecting  papillae,  called 
villi.  The  villi  are  of  two  kinds,  cylindrical  and  laminated,  and  so  abund- 
ant, as  to  give  to  the  entire  surface  a  beautiful  velvety  appearance.1  In 
the  large  intestine,  the  surface  is  composed  of  a  fine  network  of  minute 
polyhedral  cells,  more  numerous  and  minute  than  those  of  the  stomach. 
The  deeper  layer  of  the  corium  is  a  cellulo-fibrous  structure,  in  which  the 
vessels  and  nerves  ramify  previously  to  their  termination  in  the  super- 
ficial layer. 

Glands. — In  the  loose  cellular  tissue  connecting  the  mucous  with  the 
fibrous  layer,  are  situated  the  glands  and  follicles  belonging  to  the 
mucous  membrane ;  these  are  the — 

Gastric  follicles, 

Duodenal  glands  (Brunner's), 

Glandulae  solitarise, 

Glandulae  aggregatae  (Peyer's), 

Simple  follicles  (Lieberkiihn's). 

The  gastric  follicles  are  long  tubular  follicular  glands,  situated  perpen- 
dicularly side  by  side  in  every  part  of  the  mucous  membrane  of  the 
stomach.  At  their  terminations  they  are  dilated  into  small  lateral 
pouches,  which  give  them  a  clustered  appearance.  This  character  is 


1  Krause  estimates  the  number  of  villi  in  a  square  line  in  the  upper 
part  of  the  small  intestine  at  fifty  to  ninety ;  and  lower  down,  forty  to 
seventy ;  the  total  for  the  whole  length  of  the  intestine  being  four  mil- 
lions. 


68  THE   DISSECTOR. 

more  clearly  exhibited  at  the  pyloric  than  at  the  cardiac  end  of  the 
stomach.  They  are  intended,  very  probably,  for  the  secretion  of  the 
gastric  fluid.1 

The  duodenal,  or  Brunner^s  glands,  are  small  flattened  granular  bodies, 
compared  collectively  by  Von  Brunn  to  a  second  pancreas.  They  re- 
semble in  structure  the  .small  salivary  glands,  so  abundant  beneath  the 
mucous  membrane  of  the  mouth  and  lips ;  and,  like  them,  they  open 
upon  the  surface  by  minute  excretory  ducts.  They  are  limited  to  the 
duodenum  and  commencement  of  the  jejunum. 

The  solitary  glands  are  of  two  kinds,  those  of  the  small  and  those  of 
the  large  intestine.  The  former  are  small  circular  whitish  and  slightly 
prominent  patches,  surrounded  by  a  zone  or  wreath  of  simple  follicles. 
When  opened,  they  are  seen  to  consist  of  a  small  flattened  saccular 
cavity,  containing  a  mucous  secretion,  but  having  no  excretory  duct. 
They  are  found  in  all  parts  of  the  small  intestines. 

The  solitary  glands  of  the  large  intestine  are  most  abundant  in  the 
caecum  and  appendix  cseci ;  they  are  small  circular  prominences,  flattened 
upon  the  surface,  and  perforated  in  the  centre  by  a  minute  excretory 
opening.2 

The  aggregate,  or  Peyer's  glands,  are  situated  in  the  lower  part  of  the 
jejunum  and  in  the  ileum,  but  chiefly  in  the  lower  part  of  the  latter. 
They  are  collected  into  patches,  which  are  small  and  circular,  and  few 
in  number,  in  the  upper  part  of  the  bowel,  and  large  and  oblong  or  oval 
below,  and  occupy  that  portion  of  the  intestine  which  is  opposite  the 
attachment  of  the  mesentery.  To  the  naked  eye  they  present  the  ap- 
pearance of  pale  disks,  covered  with  small  irregular  fissures ;  but  with 
the  aid  of  the  microscope  they  are  seen  to  be  composed  of  numerous 
small  circular  patches,  surrounded  by  simple  follicles,  like  the  solitary 
glands  of  the  small  intestine.  Each  patch  corresponds  with  a  flattened 
and  closed  sac,  situated  beneath  the  membrane,  but  having  no  excretory 
opening,  and  containing  a  small  quantity  of  a  whitish  pulp.  The  inter- 
space between  the  patches  is  occupied  by  villi. 

The  simple  follicles  or  crypts  of  Lieberkiihn,  are  small  csecal  pouches 
of  the  mucous  layer,  dispersed  in  immense  numbers  over  every  part  of 
the  mucous  membrane,  and  opening  on  the  surface  by  round  apertures. 
In  the  large  intestine,  they  are  longer  and  more  numerous  than  in  the 
small. 

Vessels  and  Nerves. — The  arteries  of  the  abdominal  portion  of 
the  alimentary  canal  form  a  chain  of  communications  along  the 
tube,  which  is  continued  upwards  to  the  pharynx  and  mouth  ; 
they  are,  the  gastric,  hepatic,  splenic,  superior  mesenteric,  and 
inferior  mesenteric.  The  veins  unite  to  form  the  vena  portae. 
The  lymphatics  and  lacteals  open  into  the  thoracic  duct. 

The  nerves  of  the  stomach  are  the  pneumogastric,  and  sym- 
pathetic branches  from  the  solar  plexus ;  those  of  the  intestinal 
canal  are  the  superior  and  inferior  mesenteric,  and  hypogastric 
plexuses.  The  extremity  of  the  rectum  is  supplied  by  the  inferior 
sacral  nerves  from  the  spinal  cord. 

1  John  Conrad  Peyer,  an  anatomist  of  Schaffhausen,  in  Switzerland. 
His  essay,  "  De  Glandulis  Intestinorum,"  was  published  in  1677. 

2  John  Conrad  von  Brunn ;  "  Gland ulse  Duodeni  seu  Pancreas  Secun- 
darium,"  1715. 


SUPERIOR   MESENTERIC   ARTERY. 


69 


Dissection. — The  student  should  now  raise  the  transverse  colon,  and 
pin  it  upwards  upon  the  chest.  He  should  then  draw  the  whole  of  the 
small  intestines  over  to  the  left  side.  Then  let  him  dissect  the  peritoneal 
l:m-r  from  the  middle  line,  opposite  the  third  lumbar  vertebra,  and  he 
will  expose  the  superior  mesenteric  artery,  and  by  its  side  the  superior 
mesenteric  vein.  The  branches  of  the  artery  should  be  carefully  cleared 
of  fat  and  cellular  tissue.  In  the  progress  of  the  dissection  nervous  fila- 
ments, lacteals,  and  lymphatic  glands  will  be  exposed. 

The  SUPERIOR  MESENTERIC  ARTERY,  the  second  of  the  single 
trunks  given  off  by  the  abdominal  aorta,  and  next  in  size  to  the 
cceliac  axis,  arises  from  the  aorta  immediately  below  the  latter 
vessel,  and  behind  the  pancreas.  It  passes  forwards  between  the 

Fig.  20. 


THE  COURSE  AND  DISTRIBUTION  OP  THE  SUPERIOR  MESENTERIC  ARTERT. — 
1.  The  descending  portion  of  the  duodenum.  2.  The  transverse  portion.  3. 
The  pancreas.  4.  The  jejunum.  5.  The  ileum.  6.  The  caecum,  from  which 
tin-  .'tppendix  veriniformis  is  seen  projecting.  7.  The  ascending  colon.  8.  The 
transverse  colon.  9.  The  commencement  of  the  descending  colon.  10.  The 
superior  mesenteric  artery.  11.  The  colica  media.  12.  The  branch  which 
inosculates  with  the  colica  sinistra.  13.  The  branch  of  the  superior  mesenterio 
artery,  which  inosculates  with  the  pancreatico-duodenalis.  14.  The  colica 
dextra.  15.  The  ileo-colica.  16,  16.  The  branches  from  the  convexity  of  the 
superior  mesenteric  to  the  email  intestines. 


70  THE   DISSECTOR. 

pancreas  and  transverse  duodenum,  and  descends  within  the 
layers  of  the  mesentery,  to  the  right  iliac  fossa,  where  it  termi- 
nates, very  much  diminished  in  size.  It  forms  a  curve  in  its 
course,  the  convexity  being  directed  towards  the  left,  and  the 
concavity  to  the  right.  It  is  in  relation  near  its  commencement 
with  the  portal  vein  ;  and  is  accompanied  by  two  veins,  and  the 
superior  mesenteriq  plexus  of  nerves. 

The  branches  of  the  superior  mesenteric  artery  are — 
Yasa  intestini  tenuis,  Colica  dextra, 

Ileo-colica,  Colica  media. 

The  vasa  intestini  tenuis  arise  from  the  convexity  of  the  supe- 
rior mesenteric  artery.  They  vary  from  fifteen  to  twenty  in 
number,  and  are  distributed  to  the  small  intestine,  from  the  duo- 
denum to  the  termination  of  the  ileum.  In  their  course  between 
the  layers  of  the  mesentery,  they  form  a  series  of  arches  by  the 
inosculation  of  their  larger  branches ;  from  these  are  developed 
secondary  arches,  and  from  the  latter  a  third  series  of  arches, 
from  which  the  branches  arise  which  are  distributed  to  the  coats 
of  the  intestine.  From  the  middle  branches  a  fourth,  and  some- 
times even  a  fifth  series  of  arches  is  produced.  By  means  of 
these  arches  a  direct  communication  is  established  between  all 
the  branches  given  off  from  the  convexity  of  the  superior  mesen- 
teric artery  ;  a  superior  branch  (inferior  pancreatico-duodenalis} 
supplies  the  pancreas  and  duodenum,  and  inosculates  with  the 
pancreatico-duodenalis,  and  the  inferior  unites  with  the  ileo- 
colica. 

The  ileO'Colic  artery  is  the  last  branch  given  off  from  the  con- 
cavity of  the  superior  mesenteric.  It  descends  to  the  right  iliac 
fossa,  and  divides  into  branches  which  communicate  and  form 
arches,  from  which  branches  are  distributed  to  the  termination 
of  the  ileum,  the  ca3cum,  and  the  commencement  of  the  colon. 
This  artery  inosculates  on  the  one  hand  with  the  termination  of 
the  mesenteric  trunk,  and  on  the  other  with  the  colica  dextra. 

The  colica  dextra  arises  from  about  the  middle  of  the  con- 
cavity of  the  superior  mesenteric,  and  passing  outwards  behind 
the  peritoneum,  divides  into  branches  which  form  arches,  and 
are  distributed  to  the  ascending  colon.  Its  descending  branches 
inosculate  with  the  ileo-colica,  and  the  ascending  with  the  colica 
media. 

The  colica  media  arises  from  the  upper  part  of  the  concavity 
of  the  superior  mesenteric,  and  passes  forward  between  the  layers 
of  the  transverse  mesocolon,  where  it  forms  arches,  and  is  distri- 
buted to  the  transverse  colon.  It  inosculates  on  the  right  with 
the  colica  dextra;  and  on  the  left  with  the  colica  sinistra,  a 
branch  of  the  inferior  mesenteric  artery. 


INFERIOR   ME6ENTERIC   ARTERY.  71 

The  SUPERIOR  MESENTERIC  VEIN  is  formed  by  branches  which 
collect  the  venous  blood  from  the  capillaries  of  the  superior  rae- 
senteric  artery ;  they  constitute,  by  their  junction,  a  large  trunk, 
which  ascends  by  the  side  of  the  artery,  crosses  the  transverse 
portion  of  the  duodenum,  and  unites  behind  the  pancreas  with 
the  splenic  in  the  formation  of  the  portal  vein. 

The  LYMPHATIC  VESSELS  and  GLANDS  of  the  small  intestine  are 
situated  between  the  layers  of  the  mesentery.  The  glands  occupy 
the  meshes  of  the  branches  of  the  artery,  and  are  named  mesen- 
teric  glands.  They  are  most  numerous  and  largest  superiorly, 
near  the  duodenum  ;  and  inferiorly,  near  the  termination  of  the 
ileum.  The  lymphatic  vessels  are  of  two  kinds :  those  of  the 
structure  of  the  intestines,  which  run  upon  its  surface  previously 
to  entering  the  mesenteric  glands ;  and  those  which  commence 
in  the  villi,  in  the  substance  of  the  mucous  membrane,  and  are 
named  lacteals. 

The  lacteals,  according  to  Henle,  commence  in  the  centre  of 
each  villus  as  a  caecal  tubulus,  which  opens  into  a  fine  network, 
situated  in  the  submucous  tissue.  From  this  areolar  network 
the  lacteal  vessels  proceed  to  the  mesenteric  glands,  and  from 
thence  to  the  thoracic  duct,  in  which  they  terminate. 

The  NERVES  of  the  small  intestines  are  the  mesenteric  plexus. 

Dissection. — The  small  intestines  should  now  be  removed  by  cutting 
through  the  mesentery  near  its  intestinal  border,  and  placing  a  ligature 
around  the  jejunum  at  its  commencement,  and  another  around  the  ileum 
near  its  termination.  They  may  then  be  set  aside  for  the  purpose  of  exa- 
mining their  interior,  and  the  arrangement  of  the  mucous  membrane,  at 
a  convenient  moment.  It  would  be  desirable  also  that  the  student  should 
innate  a  portion  of  the  upper  part  of  the  jejunum,  and  of  the  lower  part 
of  the  ileum,  that  he  may  observe  their  appearance  when  dry.  The  val- 
vulae  conniventes  will  thus  form  a  pretty  and  useful  preparation.  Then 
dissect  carefully  the  anterior  layer  of  the  left  mesocolon;  the  inferior 
mesenteric  artery,  with  its  branches,  will  be  brought  into  view. 

The  INFERIOR  MESENTERIC  ARTERY,  smaller  than  the  superior, 
arises  from  the  abdominal  aorta,  about  two  inches  below  the 
origin  of  that  vessel,  and  descends  between  the  layers  of  the  left 
mesocolon,  to  the  left  iliac  fossa,  where  it  divides  into  three 
branches : — 

Colica  sinistra,  Sigmoid, 

Superior  hemorrhoidal. 

The  colica  sinistra  is  distributed  to  the  descending  colon ;  it 
passes  upwards  and  outwards  behind  the  peritoneum,  and  divides 
into  two  branches,  one  of  which  ascends  to  inosculate  with  the 
colica  media,  while  the  other  descends  to  communicate  with  the 
sigmoid  branch.  The  inosculation  of  the  colica  sinistra  with 
the  colica  media  is  the  largest  arterial  anastomosis  in  the  body. 


THE   DISSECTOR. 


The  sigmoid  artery  passes  obliquely  outwards  behind  the  peri- 
toneum, and  divides  into  branches  which  form  arches,  and  are 
distributed  to  the  sigmoid  flexure  of  the  colon.  The  superior 

Fig.  21. 


THE  DISTRIBUTION  AND  BRANCHES  OF  THE  INFERIOR  MESENTERIC  ARTERY. — 
1,  1.  The  superior  mesenteric  artery,  with  its  branches  and  the  small  intestines 
turned  over  to  the  right  side.  2.  The  caecum  and  appendix  caeci.  3.  The 
ascending  colon.  4.  The  transverse  colon  raised  upwards.  5.  The  descending 
colon.  6.  Its  sigmoid  flexure.  7.  The  rectum.  8.  The  aorta.  9.  The  infe- 
rior mesenteric  artery.  10.  The  colica  sinistra,  inosculating  with  11,  the  colica 
media,  a  branch  of  the  superior  mesenteric  artery.  12,  12.  Sigmoid  branches. 
13.  The  superior  hemorrhoidal  artery.  14.  The  pancreas.  15.  The  descend- 
ing portion  of  the  duodenum. 

branch  inosculates  with  the  colica  sinistra,  the  inferior  with  the 
superior  hemorrhoidal  artery. 

The  superior  hemorrhoidal  artery  is  the  continuation   of  the 
inferior  mesenteric.     It  crosses  the  ureter  and  common  iliac  ar- 


MESENTERIC   VEIN  —  HEPATIC   ARTERY.  73 

tery  of  the  left  side,  and  descends  between  the  two  layers  of  the 
mesorectum  as  far  as  the  middle  of  the  rectum  to  which  it  is 
distributed,  anastomosing  with  the  middle  and  external  heinor- 
rhoidal  arteries. 

The  INFERIOR  MESENTERIC  VEIN  receives  its  blood  from  the  rec- 
tum by  means  of  the  hemorrhoidal  veins,  and  from  the  sigmoid 
flexure  and  descending  colon,  and  ascends  behind  the  transverse 
duodenum  and  pancreas,  to  terminate  in  the  splenic  vein.  Its 
hemorrhoidal  branches  inosculate  with  branches  of  the  internal 
iliac  vein,  and  thus  establish  a  communication  between  the  portal 
and  general  venous  system. 

The  LYMPHATIC  GLANDS  of  the  large  intestines  (mesocolic)  are 
situated  along  the  attached  margin  of  the  intestine,  in  the  meshes 
formed  by  the  colic  and  hemorrhoidal  arteries  previously  to  their 
distribution.  The  lymphatic  vessels  take  their  course  in  two 
different  directions ;  those  of  the  caecum,  ascending  and  transverse 
colon,  after  traversing  their  proper  glands,  proceed  to  the  mesen- 
teric ;  and  those  of  the  descending  colon  and  rectum,  to  the 
lumbar  glands. 

The  NERVES  of  the  descending  colon,  sigmoid  flexure  and  rec- 
tum are  derived  from  the  inferior  mesenteric  plexus,  which  pro- 
ceeds chiefly  from  the  aortic  plexus. 

/tixsrrtion. — The  large  intestines  should  now  be  removed  altogether, 
and  a  ligature  placed  around  the  upper  part  of  the  rectum.  The  student 
should  then  pin  up  the  liver  and  innate  the  duodenum  and  stomach  with 
a  small  quantity  of  air.  The  blowpipe  may  be  inserted  for  this  purpose 
into  the  upper  part  of  the  jejunum,  which  was  left  on  the  removal  of  the 
small  intestines.  Next  remove  the  middle  portion  of  the  lesser  omentum, 
and  feel  for  the  coeliac  axis.  The  branches  of  the  coeliac  axis  should  then 
be  dissected  and  followed  to  their  distribution.  It  would  be  well  to  avoid 
disturbing  the  coeliac  axis  itself  at  present,  as  it  is  surrounded  by  the 
solar  plexus,  which  must  be  afterwards  examined. 

The  cxETJAC  AXIS  (xotxi'a,  ventricnlus)  is  the  first  single  trunk 
given  off  from  the  abdominal  aorta.  It  arises  opposite  the  upper 
border  of  the  first  lumbar  vertebra,  is  about  half  an  inch  in  length, 
and  divides  into  three  large  branches,  gastric,  hepatic,  and  splenic. 

The  GASTRIC  ARTERY  (coroiiaria  ventriculi),  the  smallest  of  the 
three  branches  of  the  cceliac  axis,  ascends  between  the  two  layers  of 
the  lesser  omentum  to  the  cardiac  orifice  of  the  stomach,  then  runs 
along  the  lesser  curvature  to  the  pylorus,  and  inosculates  with 
the  pyloric  branch  of  the  hepatic.  It  is  distributed  to  the  lower 
extremity  of  the  oesophagus  and  lesser  curve  of  the  stomach,  and 
anastomoses  with  the  oesophageal  arteries,  and  vasa  brevia  of  the 
splenic  artery. 

The  HEPATIC  ARTERY  curves  forward,  and  ascends  along  the 
right  border  of  the  lesser  omentum  to  the  liver,  where  it  divides 
into  two  branches  (right  and  left),  which  enter  the  transverse 
7 


THE   DISSECTOR. 


fissure,  and  are  distributed  along  the  portal  canals  to  the  right 
and  left  lobes.     It  is  in  relation,  in  the  right  border  of  the  lesser 

Fig.  22. 


THE  DISTRIBUTION  OF  THE  BRANCHES  OF  THE  CCELIAC  Axis. — 1.  The  liver. 
2.  Its  transverse  fissure.  3.  The  gall-bladder.  4.  The  stomach.  5.  The  entrance 
of  the  oesophagus.  6.  The  pylorus.  7.  The  duodenum,  its  descending  portion. 
8.  The  transverse  portion  of  the  duodenum.  9.  The  pancreas.  10.  The  spleen. 
11.  The  aorta.  12.  The  cceliac  axis.  13.  The  gastric  artery.  14.  The 
hepatic  artery.  15.  Its  pyloric  branch.  16.  The  gastro-duodenalis.  17.  The 
gastro-epiploica  dextra.  18.  The  pancreatico-duodenalis,  inosculating  with  a 
branch  of  the  superior  mesenteric  artery.  19.  The  division  of  the  hepatic 
artery  into  its  right  and  left  branches  ;  the  right  giving  off  the  cystic  branch. 

20.  The  splenic  artery,  traced  by  dotted  lines  behind  the  stomach  to  the  spleen. 

21.  The  gastro-epiploica  sinistra,  inosculating  along  the  great  curvature  of  the 
stomach  with  the  gastro-epiploica  dextra.    22.  The  pancreatica  magna.    23.  The 
vasa  brevia  to  the  great  end  of  the  stomach,  inosculating  with  branches  of  the 
gastric  artery.     24.  The  superior  mesenteric  artery,  emerging  from  between  the 
pancreas  and  transverse  portion  of  the  duodenum. 

omentum,  with  the  duetus  communis  choledochus  and  portal  vein, 
and  is  surrounded  by  the  hepatic  plexus  of  nerves  and  numerous 
lymphatics.     There  are  sometimes  two  hepatic  arteries,  in  which 
case  one  is  derived  from  the  superior  mesenteric  artery. 
The  branches  of  the  hepatic  artery  are,  the — • 
Pyloric, 

Gastro-duodenalis,  j  Gastro-epiploica  dextra, 
'    (Pancreatico-duodenalis, 
Cystic. 


SPLENIC  ARTERY.  75 

The  pyloric  branch,  given  off  from  the  hepatic  near  the  pylorus, 
is  distributed  to  the  commencement  of  the  duodenum  and  to  the 
lesser  curve  of  the  stomach,  where  it  inosculates  with  the  gastric 
artery. 

The  gastro-duodenalis  artery  is  a  short  but  large  trunk,  which 
descends  behind  the  pylorus,  and  divides  into  two  branches,  the 
gastro-epiploica  dextra,  and  pancreatico-duodenalis.  Previously 
to  its  division,  it  gives  off  some  inferior  pyloric  branches  to  the 
small  end  of  the  stomach. 

The  gastro-epiploica  dextra  runs  along  the  great  curve  of  the 
stomach  lying  between  the  two  layers  of  the  great  omentura,  and 
inosculates  at  about  its  middle  with  the  gastro-epiploica  sinistra, 
a  branch  of  the  splenic  artery.  It  supplies  the  great  curve  of 
the  stomach,  and  great  omentum ;  hence  its  name. 

The  pancreatico-duodenalis  curves  along  the  fixed  border  of 
the  duodenum,  partly  concealed  by  the  attachment  of  the  pancreas, 
and  is  distributed  to  the  pancreas  and  duodenum.  It  inosculates 
below  with  the  inferior  pancreatico-duodenalis  and  pancreatic 
branches  of  the  superior  mesenteric  artery. 

The  cystic  artery,  generally  a  branch  of  the  right  hepatic,  is  of 
small  size,  and  ramifies  between  the  coats  of  the  gall-bladder, 
previously  to  its  distribution  to  the  mucous  membrane. 

The  SPLENIC  ARTERY,  the  largest  of  the  three  branches  of  the 
cooliac  axis,  passes  horizontally  to  the  left  along  the  upper  border 
of  the  pancreas,  and  divides  into  five  or  six  large  branches,  which 
enter  the  hilus  of  the  spleen,  and  are  distributed  to  its  structure. 
In  its  course  it  is  tortuous  and  serpentine,  and  frequently  makes 
a  complete  turn  upon  itself.  It  lies  in  a  narrow  groove  in  the 
upper  border  of  the  pancreas,  and  is  accompanied  by  the  splenic 
vein,  which  lies  beneath  it,  and  by  the  splenic  plexus  of  nerves. 

The  branches  of  the  splenic  artery  are,  the — 
Pancreaticae  parva),  Yasa  brevia, 

Pancreatica  magna,  Gastro-epiploica  sinistra. 

The  pancreaticce  parvce  are  numerous  small  branches  distri- 
buted to  the  pancreas,  as  the  splenic  artery  runs  along  its  upper 
border.  One  of  these,  larger  than  the  rest,  follows  the  course  of 
the  pancreatic  duct,  and  is  called  pancreatica  magna. 

The  vasa  brevia  are  five  or  six  branches  of  small  size  which 
pass  from  the  extremity  of  the  splenic  artery  and  its  terminal 
branches,  between  the  layers  of  the  gastro-splenic  omentum,  to 
the  <rreat  end  of  the  stomach,  to  which  they  are  distributed,  inos- 
culating with  branches  of  the  gastric  artery  and  gastro-epiploica 
sinistra. 

The  gastro-epiploica  sinistra  appears  to  be  the  continuation  of 
the  splenic  artery ;  it  passes  forwards  from  left  to  right,  along 


76  THE   DISSECTOR. 

the  great  curve  of  the  stomach,  lying  between  the  layers  of  the 
great  omentum,  and  inosculates  with  the  gastro-epiploica  dextra. 
It  is  distributed  to  the  greater  curve  of  the  stomach  and  to  the 
great  omentum. 

The  GASTRIC  VEINS,  corresponding  with  the  gastric,  gastro- 
epiploic,  and  vasa  brevia  arteries,  terminate  in  the  splenic  vein; 

The  SPLENIC  VEIN  commences  in  the  structure  of  the  spleen, 
and  quits  that  organ  by  several  large  veins ;  it  is  larger  than 
the  splenic  artery,  and  perfectly  straight  in  its  course.  It  passes 
horizontally  inwards  behind  the  pancreas,  and  terminates  near  its 
greater  end  by  uniting  with  the  superior  mesenteric  and  forming 
the  portal  vein.  It  receives  in  its  course  the  gastric  and  pan- 
creatic veins,  and  near  its  termination  the  inferior  mesenteric 
vein. 

The  NERVES  which  accompany  the  branches  of  the  coeliac  axis 
are  derived  from  the  solar  plexus,  and  constitute  the  gastric, 
hepatic,  and  splenic  plexus. 

The  relations  of  the  vessels  situated  in  the  right  border  of  the  lesser 
omentum  should  now  be  examined  more  particularly.  The  hepatic 
artery  will  be  found  to  the  left,  the  ductus  communis  choledochus  to  the 
right,  and  the  portal  vein  behind  and  between  them.  The  student  will 
also  perceive  how  the  lower  boundary  of  the  foramen  of  Wiiislow  is 
formed  by  the  hepatic  artery. 

The  ductus  communis  choledochus  (xo^,  bilis,  &E£O/UU,  recipio) 
is  the  common  excretory  duct  of  the  liver  and  gall-bladder.  It 
is  about  three  inches  in  length,  and  is  formed  by  the  junction  of 
the  hepatic  with  the  cystic  duct.  It  descends  through  the  right 
border  of  the  lesser  omentum,  and  behind  the  descending  por- 
tion of  the  duodenum  to  the  inner  side  of  that  intestine,  where  it 
terminates  by  passing  obliquely  between  the  muscular  and  mu- 
cous coat,  and  opening  on  the  summit  of  a  papilla  which  is  com- 
mon to  it  and  the  pancreatic  duct.  The  papilla  is  situated  near 
the  lower  part  of  the  descending  portion  of  the  duodenum  on  its 
inner  side  ;  and  the  duct  is  constricted  in  size  during  its  passage 
between  the  coats  of  the  intestine. 

The  ductus  communis  choledochus,  hepatic  artery,  and  portal  vein  are 
surrounded  and  held  together,  while  in  the  right  border  of  the  lesser 
omentum,  by  loose  cellular  tissue,  which  is  continued  with  the  vessels 
into  the  substance  of  the  liver,  and  is  termed  Glisson's  capsule.  In  this 
Glisson's  capsule  are  also  contained  a  number  of  large  lymphatic  vessels 
which  are  taking  their  course  from  the  liver  and  gall-bladder  to  the 
lumbar  glands. 

If  the  hepatic  artery  and  ductus  communis  choledochus  be  drawn 
aside,  and  the  connecting  cellular  tissue  removed,  the  portal  vein  will  be 
brought  into  view,  lying  between  and  behind  the  duct  and  artery. 

The  VENA  PORT^E,  formed  by  the  union  of  the  splenic  and 
superior  mesenteric  vein  behind  the  pancreas,  is  about  three 


THE   LIVER.  IT 

inches  in  length.  It  ascends  through  the  right  border  of  the 
lesser  omentura  to  the  transverse  fissure  of  the  liver,  where  it 
divides  into  two  branches,  one  for  each  lateral  lobe.  In  the  right 
border  of  the  lesser  omentum  it  is  situated  behind  and  between 
the  hepatic  artery  and  ductus  communis  choledochus,  and  is  sur- 
rounded by  the  hepatic  plexus  of  nerves  and  lymphatics.  At  the 
transverse  fissure  each  primary  branch  divides  into  numerous 
secondary  branches  which  ramify  through  the  portal  canals,  and 
give  off  vaginal  and  interlobular  veins,  and  the  latter  terminate 
in  the  lobular  venous  plexus  of  the  lobules  of  the  liver.  The 
portal  vein  within  the  liver  receives  the  venous  blood  from  the 
capillaries  of  the  hepatic  artery. 

The  student  may  now  proceed  to  examine  the  liver ;  firstly  in  situ, 
with  a  view  to  its  connections  and  relations,  afterwards  on  its  removal 
from  the  body.  In  effecting  its  removal  he  will  have  to  cut  through  the 
ligaments  which  connect  it  to  the  abdominal  parietes  and  diaphragm 
above  and  in  front,  and  the  parts  contained  in  the  right  border  of  the 
lesser  omentum  and  inferior  vena  cava  below  and  behind. 

THE   LIVER. 

The  liver  is  a  conglomerate  gland  of  large  size,  appended  to 
the  alimentary  canal,  and  performing  the  double  office  of  sepa- 
rating impurities  from  the  venous  blood  of  the  chylopoietic  vis- 
Fig.  23. 


A  VIEW  OF  THE  LIVER  IN  SITU,  TOGETHER  WITH  THE  PARTS  ADJOINING,  IN 
A  XKW-BOHX  INFANT. — 1,  1.  The  integuments  of  the  abdomen  turned  back. 
2,  2.  The  thoracic  surface  of  a  section  of  the  diaphragm.  3.  Anterior  face 
of  the  right  lobe  of  the  liver.  4.  The  left  lobe.  5.  The  suspensory  ligament. 
6.  The  round  ligament.  7.  Point  of  origin  of  the  coronary  ligament.  8.  The 
spleen.  9.  Section  of  the  stomach.  10.  Upper  portion  of  the  colon. 

cera  previously  to  its  return  into  the  general  venous  circulation, 
and  of  secreting  a  fluid  necessary  to  chyljfication,  tjie  bile.     It 

7* 


78  THE   DISSECTOR. 

is  the  largest  organ  in  the  body,  weighing  about  four  pounds, 
and  measuring  through  its  longest  diameter  about  twelve  inches. 
It  is  situated  in  the  right  hypochondriac  region,  and  extends 
across  the  epigastrium  into  the  left  hypochondrium,  frequently 
reaching,  by  its  left  extremity,  the  upper  end  of  the  spleen.  It 
is  placed  obliquely  in  the  abdomen ;  its  convex  surface  looking 
upwards  and  forwards,  the  concave  downwards  and  backwards. 
The  anterior  border  is  sharp  and  free,  and  marked  by  a  deep 
notch,  the  posterior  rounded  and  broad.  It  is  in  relation,  supe- 
riorly and  posteriorly,  with  the  diaphragm ;  inferiorly,  with  the 
stomach,  ascending  portion  of  the  duodenum,  transverse  colon, 
right  supra-renal  capsule,  and  right  kidney;  and  corresponds, 
by  its  free  border,  with  the  lower  margin  of  the  ribs. 

Ligaments. — The  liver  is  retained  in  its  place  by  five  liga- 
ments ;  four  of  which  are  duplicatures  of  the  peritoneum,  situated 
on  the  convex  surface  of  the  organ  ;  the  fifth  is  a  fibrous  cord 
which  passes  through  a  fissure  in  its  under  surface,  from  the  um- 
bilicus to  the  inferior  vena  cava.  They  are,  the — 
Longitudinal,  Coronary, 

Two  lateral,  Round. 

The  longitudinal  ligament  (broad,  ligamentum  suspensorium 
hepatis),  is  an  antero-posterior  fold  of  peritoneum,  extending 
from  the  notch  on  the  anterior  margin  of  the  liver  to  its  poste- 
rior border.  Between  its  two  layers,  in  the  anterior  and  free 
margin,  is  the  round  ligament. 

The  lateral  ligaments  are  formed  by  the  two  layers  of  perito- 
neum, which  pass  from  the  under  surface  of  the  diaphragm  to 
the  posterior  border  of  the  liver;  they  correspond  with  its  lateral 
lobes. 

The  coronary  ligament  is  formed  by  the  separation  of  the  two 
layers  forming  the  lateral  ligaments  near  their  point  of  con- 
vergence. The  posterior  layer  is  continued  unbroken  from  one 
lateral  ligament  into  the  other ;  but  the  anterior  quits  the  pos- 
terior at  each  side,  and  is  continuous  with  the  corresponding 
layer  of  the  longitudinal  ligament.  In  this  way  a  large  oval 
surface  on  the  posterior  border  of  the  liver  is  left  uncovered  by 
peritoneum,  and  is  connected  to  the  diaphragm  by  cellular  tissue. 
This  space  is  formed  principally  by  the  right  lateral  ligament, 
and  is  pierced  near  its  left  extremity  by  the  inferior  vena  cava, 
previously  to  the  passage  of  that  vessel  through  the  tendinous 
opening  in  the  diaphragm. 

The  round  ligament  is  a  fibrous  cord  resulting  from  the  oblite- 
ration of  the  umbilical  vein,  and  situated  between  the  two  layers 
of  peritoneum  in  the  anterior  border  of  the  longitudinal  ligament. 
It  may  be  traced  from  the  umbilicus,  through  the  longitudinal 


THE   LIVER. 


79 


fissure  of  the  under  surface  of  the  liver  to  the  inferior  vena  cava, 
to  which  it  is  connected. 

Fig.  24. 

THE  UNDER  SURFACE 
OP  THE  LIVER. — 1.  The 
right  lobe.  2.  The  left 
lobe.  3.  The  lobus 
- 1  MM  '1  ni  t  us.  4.  The  lobus 
Spigelii.  5.  The  lobus 
caudatus.  6.  The  longi- 
tudinal fissure  ;  the  nu- 
meral is  placed  on  the 
rounded  cord,  the  re- 
mains of  the  umbilical 
veins.  7.  The  pons  he- 
patis.  8.  The  fissure  for 
the  ductus  venosus  ;  the 
obliterated  cord  of  the 
ductus  is  seen  passing 
backwards  to  be  at- 
tached to  the  coats  of 

the  inferior  vena  cava  (9).  10.  The  gall-bladder  lodged  in  its  fossa.  11.  The 
transverse  fissure,  containing,  from  before  backwards,  the  hepatic  duct,  hepatic 
artery,  and  portal  vein.  12.  The  vena  cava.  13.  A  depression  corresponding 
with  the  curve  of  the  colon.  14.  A  double  depression  produced  by  the  right 
kidney  and  its  supra-renal  capsule.  15.  The  rough  surface  on  the  posterior 
border  of  the  liver  left  uncovered  by  peritoneum  ;  the  cut  edge  of  peritoneum 
surrounding  this  surface  forms  part  of  the  coronary  ligament.  16.  The  notch 
on  the  anterior  border,  separating  the  two  lobes.  17.  The  notch  on  the  poste- 
rior border,  corresponding  with  the  vertebral  column. 

Fissures. — The  under  surface  of  the  liver  is  marked  by  five 
fissures,  which  divide  its  surface  into  five  compartments  or  lobes, 
two  principal  and  three  minor  lobes  ;  they  are,  the — 

Fissures. 

Transverse  fissure, 

Fissure  for  the  gall-bladder, 

Longitudinal  fissure, 

Fissure  of  the  ductus  venosus, 

Fissure  for  the  vena  cava. 

Lobes. 

Right  lobe,  Lobus  quadratus, 

Left  lobe,  Lobus  Spigelii, 

Lobus  caudatus. 

The  longitudinal  fssure  is  a  deep  groove  running  from  the 
notch  upon  the  anterior  margin  of  the  liver,  to  the  posterior 
border  of  the  organ.  At  about  one-third  from  its  posterior  ex- 
tremity it  is  joined  by  a  short  but  deep  fissure,  the  transverse, 
which  meets  it  transversely  from  the  under  part  of  the  right 
lobe. 

The  longitudinal  fissure  in  front  of  this  junction  lodges  the 


80  THE   DISSECTOR. 

fibrous  cord  of  the  umbilical  vein,  and  is  generally  crossed  by  a 
band  of  hepatic  substance  called  the  pons  hepatis. 

The  fissure  for  the  ductus  venosus  is  the  shorter  portion  of  the 
longitudinal  fissure,  extending  from  the  junctional  termination  of 
the  transverse  fissure  to  the  posterior  border  of  the  liver,  and 
containing  a  small  fibrous  cord,  the  remains  of  the  ductus  veno- 
sus. This  fissure  is,  therefore,  but  a  part  of  the  longitudinal 
fissure. 

The  transverse  fissure  is  the  short  and  deep  fissure,  about  two 
inches  in  length,  through  which  the  hepatic  ducts  quit,  and  the 
hepatic  artery  and  portal  vein  enter  the  liver.  Hence  this  fissure 
was  considered  by  the  older  anatomists  as  the  gate  (porta)  of  the 
liver;  and  the  large  vein  entering  the  organ  at  this  point,  the 
portal  vein.  At  their  entrance  into  the  transverse  fissure  the 
branches  of  the  hepatic  duct  are  the  most  anterior,  next  those  of 
the  artery,  and  most  posteriorly  the  portal  vein. 

The  fissure  for  the  gall-bladder  is  a  shallow  fossa  extending 
forwards,  parallel  with  the  longitudinal  fissure,  from  the  right 
extremity  of  the  transverse  fissure  to  the  free  border  of  the  liver, 
where  it  frequently  forms  a  notch. 

The  fissure  for  the  vena  cava  is  a  deep  and  short  fissure,  occa- 
sionally a  circular  tunnel,  which  proceeds  from  a  little  behind  the 
right  extremity  of  the  transverse  fissure  to  the  posterior  border 
of  the  liver,  and  lodges  the  inferior  vena  cava. 

These  five  fissures  taken  collectively  resemble  an  inverted  y,  the  base 
corresponding  with  the  free  margin  of  the  liver,  and  the  apex  with  its 
posterior  border.  Viewing  them  in  this  way,  the  two  anterior  branches 
represent  the  longitudinal  fissure  on  the  left,  and  the  fissure  for  the  gall- 
bladder on  the  right'side ;  the  two  posterior,  the  fissure  for  the  ductus 
venosus  on  the  left,  and  the  fissure  for  the  vena  cava  on  the  right  side ; 
and  the  connecting  bar,  the  transverse  fissure. 

Lobes. — The  right  lobe  is  four  or  six  times  larger  than  the  left, 
from  which  it  is  separated  on  the  concave  surface,  by  the  longi- 
tudinal fissure,  and,  on  the  convex,  by  the  longitudinal  ligament. 
It  is  marked  upon  its  under  surface  by  the  transverse  fissure,  and 
by  the  fissures  for  the  gall-bladder  and  vena  cava ;  and  presents 
three  depressions,  one,  in  front,  for  the  curve  of  the  ascending 
colon  (impressio  colica),  and  two,  behind,  for  the  right  supra- 
renal capsule  and  kidney  (impressio  renalis). 

The  left  lobe  is  small  and  flattened,  convex  upon  its  upper  sur- 
face, and  concave  below,  where  it  lies  in  contact  with  the  ante- 
rior surface  of  the  stomach.  It  is  sometimes  in  contact  by  its 
extremity  with  the  upper  end  of  the  spleen,  and  is  in  relation, 
by  its  posterior  border,  with  the  cardiac  orifice  of  the  stomach 
and  left  pneumogastric  nerve. 

The  lobus  quadratas  is  a  quadrilateral  lobe  situated  on  the 


THE   LIVER.  81 

under  surface  of  the  right  lobe :  it  is  bounded,  in  front,  by  the 
free  border  of  the  liver ;  behind,  by  the  transverse  fissure  ;  to  the 
right,  by  the  gall-bladder ;  and  to  the  left,  by  the  longitudinal 
fissure. 

The  lobus  Spigelii1  is  a  small  triangular  lobe,  also  situated  on 
the  under  surface  of  the  right  lobe:  it  is  bounded,  in  front,  by 
the  transverse  fissure ;  and,  on  the  sides,  by  the  fissures  for  the 
ductus  venosus  and  vena  cava. 

The  lobus  caudatus  is  a  small  tail-like  appendage  of  the  lobus 
Spigelii,  from  which  it  runs  outwards  like  a  crest  into  the  right 
lobe,  and  serves  to  separate  the  right  extremity  of  the  transverse 
fissure  from  the  commencement  of  the  fissure  for  the  vena  cava. 
In  some  persons  this  lobe  is  well  marked,  in  others  it  is  small 
and  ill-defined. 

Reverting  to  the  comparison  of  the  fissures  with  an  inverted  y,  it  will 
be  observed  that  the  quadrilateral  interval  in  front  of  the  transverse  bar 
represents  the  lobus  quadratus ;  the  triangular  space  behind  the  bar,  the 
lolms  Spigelii ;  and  the  apex  of  the  letter  the  point  of  union  between  the 
inferior  vena  cava  and  the  remains  of  the  ductus  venosus. 

Vessels  and  Nerves. — The  vessels  entering  into  the  structure  of  the  liver 
are  also^ire  in  number;  they  are,  the — 

Hepatic  artery,  Hepatic  veins,  Lymphatics. 

Portal  vein,  Hepatic  ducts, 

The  hepatic  artery,  portal  vein,  and  hepatic  duct  enter  the  liver  at  the 
transverse  fissure,  and  ramify  through  portal  canals  to  every  part  of  the 
organ ;  so  that  their  general  direction  is  from  below  upwards,  and  from 
the  centre  towards  the  circumference. 

The  hepatic  veins  commence  at  the  circumference,  and  proceed  from 
before  backwards,  to  open  into  the  vena  cava,  on  the  posterior  border  of 
the  liver.  Hence  the  branches  of  the  two  veins  cross  each  other  in  their 
course. 

The  portal  vein,  hepatic  artery,  and  hepatic  duct  are  moreover  enveloped 
in  a  loose  cellular  tissue  (the  capsule  of  Glisson),  which  permits  them  to 
contract  upon  themselves  when  emptied  of  their  contents ;  the  hepatic 
v.'ins,  on  the  contrary,  are  closely  adherent  by  their  parietes  to  the  surface 
of  the  canals  in  which  they  run,  and  are  unable  to  contract.  By  these 
characters  the  anatomist  is  enabled,  in  any  section  of  the  liver,  to  distin- 
guish at  once  the  most  minute  branch  of  the  portal  vein  from  an  hepatic 
vein  :  the  former  will  be  found  more  or  less  collapsed,  and  always  accom- 
panied by  an  artery  and  duct,  and  the  latter  widely  open  and  solitary. 

The  lymphatics  of  the  liver  are  divisible  into  the  deep  and  superficial. 
The  former  take  their  course  through  the  portal  canals  and  right  border 
of  the  lesser  omentum  to  the  lymphatic  glands  situated  in  the  course  of 
the  hepatic  artery,  and  along  the  lesser  curve  of  the  stomach.  The  super- 
ficial lymphatics  are  situated  in  the  cellular  structure  of  the  proper  capsule, 
over  the  whole  surface  of  the  liver.  Those  of  the  convex  surface  are  di- 


1  Adrian  Spigel,  a  Belgian  physician,  professor  at  Padua  after  Casserius 
in  ItJlG.  He  assigned  considerable  importance  to  this  little  lobe,  but  it 
was  described  by  Sylvius  full  sixty  years  before  him. 


82  THE   DISSECTOE. 

Tided  into  two  sets,  one  passing  from  before  backwards,  and  one  from, 
behind  forwards  ;  the  former  enter  the  lateral  and  coronary  ligaments, 
pierce  the  diaphragm,  and  join  the  posterior  niediastinal  glands,  or  proceed 
to  the  glands  situated  around  the  inferior  cava ;  the  latter  also  consists  of 
two  groups,  one  which  ascends  in  the  broad  ligament,  and  perforates  the 
diaphragm,  to  terminate  in  the  anterior  niediastinal  glands,  while  the  other 
curves  around  the  anterior  margin  of  the  liver  to  its  concave  surface,  and 
pursues  its  course  to  the  glands  in  the  right  border  of  the  lesser  omentum. 
The  lymphatics  of  the  concave  surface  of  the  liver  are  variously  dis- 
tributed ;  those  from  the  right  lobe  terminate  in  the  lumbar  glands  ;  those 
from  the  gall-bladder,  which  are  large,  enter  the  glands  in  the  right  bor- 
der of  the  lesser  omentum ;  and  those  from  the  left  lobe  converge  to  the 
glands  situated  along  the  lesser  curve  of  the  stomach. 

The  nerves  of  the  liver  are  derived  from  the  systems  both  of  animal  and 
organic  life  ;  the  former  proceed  from  the  right  phrenic  and  right  pneu- 
mogastric  nerve,  the  latter  from  the  hepatic  plexus. 

Structure  and  Minute  Anatomy  of  the  Liver. 

The  liver  is  composed  of  lobules,  of  a  connecting  medium  called  Glisson^s 
capsule,  of  the  ramifications  of  the  portal  vein,  hepatic  duct,  hepatic  artery, 
hepatic  veins,  lymphatics,  and  nerves,  and  is  inclosed  and  retained  in  its 
situation  by  the  peritoneum. 

The  lobules  are  small  granular  bodies  of  about  the  size  of  a  millet-seed, 
of  irregular  form,  and  presenting  a  number  of  rounded  prominences  on 
their  surface.  When  divided  longitudinally,  they  have  a  foliated  ap- 
pearance, and  transversely,  a  polygonal  outline,  with  sharp  or  rounded 
angles,  according  to  the  smaller  or  greater  quantity  of  Glisson's  capsule 
contained  in  the  liver.  Each  lobule  is  divided  upon  its  exterior  into  a 
base  and  a  capsular  surface.  The  base  corresponds  with  one  extremity 
of  the  lobule,  is  flattened,  and  rests  upon  an  hepatic  vein,  which  is  thence 
named  sublobular.  The  capsular  surface  includes  the  rest  of  the  periphery 
of  the  lobule,  and  has  received  its  designation  from  being  inclosed  in  a 
cellular  capsule  derived  from  the  capsule  of  Glisson.  In  the  centre  of 
each  lobule  is  a  small  vein,  the  intralobular,  which  is  formed  by  the  con- 
vergence of  six  or  eight  minute  veiiules  from  the  rounded  prominences  of 
the  periphery.  The  intralobular  vein  thus  constituted  takes  its  course 
through  the  centre  of  the  longitudinal  axis  of  the  lobule,  pierces  the  middle 
of  its  base,  and  opens  into  the  sublobular  vein.  The  periphery  of  the 
lobule,  with  the  exception  of  its  base,  which  is  always  closely  attached  to 
a  sublobular  vein,  is  connected  by  means  of  its  cellular  capsule  with  the 
capsular  surfaces  of  surrounding  lobules.  The  interval  between  the  lo- 
bules is  the  interlobular  fissure,  and  the  angular  interstices  formed  by  the 
apposition  of  several  lobules  are  the  interlobular  spaces. 

The  lobules  of  the  centre  of  the  liver  are  angular,  and  somewhat  smaller 
than  those  of  the  surface,  from  the  greater  compression  to  which  they  are 
submitted.  The  superficial  lobules  are  incomplete,  and  give  to  the  sur- 
face of  the  organ  the  appearance  and  all  the  advantages  resulting  from 
an  examination  of  a  transverse  section. 

"  Each  lobule  is  composed  of  a  plexus  of  biliary  ducts,  of  a  venous  plexus, 
formed  by  branches  of  the  portal  vein,  of  a  branch  (intra-lobular)  of  an 
hepatic  vein,  and  of  minute  arteries  ;  nerves  and  absorbents,  it  is  to  be 
presumed,  also  enter  into  their  formation,  but  cannot  be  traced  into  them." 
"  Examined  with  the  microscope,  a  lobule  is  apparently  composed  of  nu- 
merous minute  bodies  of  a  yellowish  color  and  of  various  forms,  connected 


STRUCTURE   OF   THE   LIVER.  83 

with  each  other  by  vessels.  These  minute  bodies  are  the  acini  of  Mal- 
pighi."  "If  an  uninjected  lobule  be  examined  and  contrasted  with  an 
injected  lobule,  it  will  be  found  that  the  acini  of  Malpighi  in  the  former 
are  identical  with  the  injected  lobular  biliary  plexus  in  the  latter,  and 
the  bloodvessels  in  both  will  be  easily  distinguished  from  the  ducts.'" 

TRANSVERSE    SECTION    OF    A  SMALL  Fig.  25. 

PORTAL  CAXAL  AND  ITS  VESSELS. — 1. 
Transverse  sections  of  the  lobules  of  the 
liver.  2.  Intra-lobular  hepatic  veins  in 
the  centres  of  the  lobules.  3.  Interlobu- 
lar  fissures,  in  which  ramify  branches  of 
the  portal  vein,  hepatic  artery,  and  hepatic 
ducts.  4.  The  portal  vein,  from  which 
pass  off  on  all  sides  interlobular  veins 
(5,  5)  which  ramify  in  the  interlobular 
fissures.  6.  The  hepatic  artery.  7.  The 
hepatic  duct.  8.  A  branch  from  each  of 
the  three  vessels  seen  entering  one  of  the 
interlobular  fissures.  9.  The  cellular  tis- 
sue, Glisscn's  capsule,  by  which  they  are 
all  surrounded.  It  will  be  observed  that 
the  boundaries  of  the  canal  in  which  the 
portal  vein  is  lodged,  are  formed  by  the 
sides  of  the  lobules  and  interlobular  fis- 
sures, and  not  by  the  bases  of  the  lobules, 
as  are  those  of  the  sub-lobular  veins. 

10.  A  lobule  in  the  state  of  "passive  congestion,"  or  "hepatic  venous  conges- 
tion." 11.  A  lobule  in  the  state  of  portal  venous  congestion.  12.  The  patches 
indicating  the  existence  of  "  active  congestion." 

Glisson's  capsule  is  the  cellulo-fibrous  tissue  which  envelops  the  hepatic 
artery,  portal  vein,  and  hepatic  duct,  during  their  passage  through  the 
right  border  of  the  lesser  omentum,  and  which  continues  to  surround 
them  to  their  ultimate  distribution  in  the  substance  of  the  lobules.  It 
forms  for  each  lobule  a  distinct  capsule,  which  invests  it  on  all  sides 
with  the  exception  of  its  base,  connects  all  the  lobules  together,  and  con- 
stitutes the  proper  capsule  of  the  entire  organ.  But  Grlisson's  capsule  is 
not  mere  cellular  tissue  ;  "  it  is  to  the  liver  what  the  pia  mater  is  to  the 
brain  ;  it  is  a  cellulo-vascular  membrane,  in  which  the  vessels  divide  and 
subdivide  to  an  extreme  degree  of  minuteness ;  which  lines  the  portal 
canals,  forming  sheaths  for  the  larger  vessels  contained  in  them,  and  a 
web  in  which  the  smaller  vessels  ramify ;  which  enters  the  interlobular 
lissures,  and  with  the  vessels  forms  the  capsules  of  the  lobules  ;  and 
\vhich  finally  enters  the  lobules,  and  with  the  bloodvessels  expands  itself 
over  the  secreting  biliary  ducts."  Hence  arises  a  natural  division  of  the 
capsule  into  three  portions,  vaginal,  interlobular,  and  lobular. 

The  vaginal  portion  is  that  which  invests  the  hepatic  artery,  hepatic 
duct,  and  portal  vein,  in  the  portal  canals ;  in  the  large  canals  it  com- 
pletely surrounds  these  vessels,  but  in  the  smaller  is  situated  only  on 
that  side  which  is  occupied  by  the  artery  and  duct.  The  interlobular 


1  The  Anatomy  and  Physiology  of  the  Liver,  by  Mr.  Kiernan,  Phil. 
Trans.,  1833,  from  which  this  and  the  other  paragraphs  within  inverted 
commas,  on  the  structure  of  the  liver,  are  quoted. 


84  THE   DISSECTOR. 

portion  occupies  the  interlobular  fissures  and  spaces,  and  the  lobular 
portion  forms  the  supporting  tissue  of  the  substance  of  the  lobules. 

The  portal  vein,  entering  the  liver  at  the  transverse  fissure,  ramifies 
through  its  structure  in  canals,  which  resemble,  by  their  surfaces,  the 
external  superficies  of  the  liver,  and  are  formed  by  the  capsular  surfaces 
of  the  lobules.  These  are  the  portal  canals,  and  contain,  besides  the 
portal  vein,  with  its  ramifications,  the  artery  and  duct  with  their  branches. 

In  the  larger  canals,  the  vessels  are  separated  from  the  parietes  by  a 
web  of  Glisson's  capsule ;  but,  in  the  smaller,  the  portal  vein  is  in  con- 
tact with  the  surface  of  the  canal  for  about  two-thirds  of  its  cylinder,  the 
opposite  third  being  in  relation  with  the  artery  and  duct  and  their  invest- 
ing capsule.  If,  therefore,  the  portal  vein  were  laid  open  by  a  longitudinal 
incision  in  one  of  these  smaller  canals,  the  coats  being  transparent,  the 
outline  of  the  lobules,  bounded  by  their  interlobular  fissures,  would  be  as 
distinctly  seen  as  upon  the  external  surface  of  the  liver,  and  the  smaller 
venous  branches  would  be  observed  entering  the  interlobular  spaces. 

The  branches  of  the  portal  vein  are,  the  vaginal,  interlobular,  and 
lobular.  The  vaginal  branches  are  those  which,  being  given  off  in  the 
portal  canals,  have  to  pass  through  the  sheath  (vagina)  of  Glisson's  cap- 
sule, previously  to  entering  the  interlobular  spaces.  In  this  course  they 
form  an  intricate  plexus,  the  vaginal  plexus,  which,  depending  for  its 
existence  on  the  capsule  of  Glisson,  necessarily  surrounds  the  vessels,  as 
does  that  capsule  in  the  larger  canals,  and  occupies  the  capsular  side  only 
in  the  smaller  canals.  The  interlobular  branches  are  given  off  from  the 
vaginal  portal  plexus  where  it  exists,  and  directly  from  the  portal  veins, 
in  that  part  of  the  smaller  canals  where  the  coats  of  the  vein  are  in  con- 
tact with  the  walls  of  the  canal.  They  then  enter  the  interlobular  spaces 
and  divide  into  branches,  which  cover  with  their  ramifications  every  part 
of  the  surface  of  the  lobules,  with  the  exception  of  their  bases  and  those 
extremities  of  the  superficial  lobules  which  appear  upon  the  surfaces  of 
the  liver.  The  interlobular  veins  communicate  freely  with  each  other, 
and  with  the  corresponding  veins  of  adjoining  fissures,  and  establish  a 
general  portal  anastomosis  throughout  the  entire  liver.  The  lobular 
branches  are  derived  from  the  interlobular  veins  ;  they  form  a  plexus 
within  each  lobule,  and  converge  from  the  circumference  towards  the 
centre,  where  they  terminate  in  the  minute  radicles  of  the  intralobular 
vein.  "  This  plexus,  interposed  between  the  interlobular  portal  veins 
and  the  intralobular  hepatic  vein,  constitutes  the  venous  part  of  the 
lobule,  and  maybe  called  the  lobular  venous  plexus."  The  irregular  islets 
of  the  substance  of  the  lobules,  seen  between  the  meshes  of  this  plexus 
by  means  of  the  microscope,  are  the  acini  of  Malpighi,  and  are  portions 
of  the  lobular  biliary  plexus. 

The  portal  vein  returns  the  venous  blood  from  the  chylopoietic  vis- 
cera, to  be  circulated  through  the  lobules ;  it  also  receives  the  venous 
blood,  which  results  from  the  distribution  of  the  hepatic  artery. 

The  hepatic  duct,  entering  the  liver  at  the  transverse  fissure,  divides 
into  branches,  which  ramify  through  the  portal  canals,  with  the  portal 
vein  and  hepatic  artery,  to  terminate  in  the  substance  of  the  lobules. 
Its  branches,  like  those  of  the  portal  vein,  are  vaginal,  interlobular,  and 
lobular. 

The  vaginal,  branches  ramify  through  the  capsule  of  Glisson,  and  form  a 
vaginal  biliari/  plexus,  which,  like  the  vaginal  portal  plexus,  surrounds  the 
vessels  in  the  large  canals,  but  is  deficient  on  that  side  of  the  smaller 
canals  near  which  the  duct  is  placed.  The  branches  given  off  by  the 
vaginal  biliary  plexus  are  interlobular  and  lobular.  The  interlobular 


STRUCTURE   OF   THE   LIVER.  85 

branches  proceed  from  the  vaginal  biliary  plexus  where  it  exists,  and 
directly  from  the  hepatic  duct  on  that  side  of  the  smaller  canals  against 
which  the  duct  is  placed.  They  enter  the  interlobular  spaces,  and  ramify 
upon  the  capsular  surface  of  the  lobules  in  the  interlobular  fissures,  where 
they  communicate  freely  with  each  other.  The  lobular  ducts  are  derived 
chiefly  from  the  interlobular ;  but  to  those  lobules  forming  the  walls  of 
the  portal  canals,  they  pass  directly  from  the  vaginal  plexus.  They  enter 
the  lobule,  and  form  a  plexus  in  its  interior,  the  lobular  biliary  plexus, 
which  constitutes  the  principal  part  of  the  substance  of  the  lobule.  The 
ducts  terminate  either  in  loops  or  in  csecal  extremities. 

The  coats  of  the  duct  are  very  vascular,  and  are  supplied  with  a  num- 
ber of  mucous  follicles,  which  are  distributed  irregularly  in  the  larger, 
but  are  arranged  in  two  parallel  longitudinal  rows  in  the  smaller  ducts. 

The  hepatic  artery  enters  the  liver  with  the  portal  veins  and  hepatic 
duct,  and  ramifies  with  those  vessels  through  the  portal  canals.  Its 
branches  are  the  vaginal,  interlobular,  and  lobular.  The  vaginal  branches, 
like  those  of  the  portal  vein  and  hepatic  duct,  form  a  vaginal  plexus, 
which  exists  throughout  the  whole  extent  of  the  portal  canals,  with  the 
exception  of  that  side  of  the  smaller  canals  which  corresponds  with  the 
artery.  The  interlobular  branches,  arising  from  the  vaginal  plexus  and 
from  the  parietal  side  of  the  artery  (in  the  smaller  canals),  ramify  through 
the  interlobular  fissures,  and  are  principally  distributed  to  the  coats  of 
the  interlobular  ducts. 

"  From  the  superficial  interlobular  fissures  small  arteries  emerge,  and 
ramify  in  the  proper  capsule,  on  the  convex  and  concave  surface  of  the 
liver,  and  in  the  ligaments.  These  are  the  capsular  arteries."  Where 
the  capsule  is  well  developed,  "  these  vessels  cover  the  surfaces  of  the 
liver  with  a  beautiful  plexus,"  and  "  anastomose  with  branches  of  the 
phrenic,  internal  mammary,  and  supra-renal  arteries,"  and  with  the  epi- 
gastrio. 

Tim  lobular  branches,  extremely  minute  and  few  in  number,  are  the 
nutrient  vessels  of  the  lobules,  and  terminate  in  the  lobular  venous 
plexus. 

All  the  venous  blood  resulting  from  the  distribution  of  the  hepatic 
artery,  even  that  from  the  vasa  vasorum  of  the  hepatic  veins,  is  returned 
into  the  portal  vein. 

The  hepatic  veins  commence  in  the  substance  of  each  lobule  by  minute 
venules,  which  receive  the  blood  from  the  lobular  venous  plexus,  and 
converge  to  form  the  intralobular  vein.  The  intralobular  vein  passes 
through  the  central  axis  of  the  lobule,  and  through  the  middle  of  its 
base,  to  terminate  in  a  sublobular  vein ;  and  the  union  of  the  sublobular 
veins  constitutes  the  hepatic  trunks,  which  open  into  the  inferior  vena 
cava.  The  hepatic  venous  system  consists,  therefore,  of  three  sets  of 
vi-<els;  intralobular  veins,  sublobular  veins,  and  hepatic  trunks. 

The  sublobular  veins  are  contained  in  canals  formed  solely  by  the  bases 
of  the  lobules,  with  which,  from  the  absence  of  Glisson's  capsule,  they 
are  in  immediate  contact.  Their  coats  are  thin  and  transparent;  and,  if 
they  be  laid  open  by  a  longitudinal  incision,  the  bases  of  the  lobules  will 
be  distinctly  seen,  separated  by  interlobular  fissures,  and  perforated 
through  the  centre  by  the  opening  of  the  intralobular  vein. 

The  hepatic  trunks  are  formed   by  the  union  of  the  sublobular  veins ; 

they  are  contained  in  canals  (hepatic-venous),  similar  in  structure  to  the 

portal  canals,  ami  lined  by  a  prolongation  of  the  proper  capsule.     They 

proceed  from  before  backwards,  and  terminate,  by  two  large  openings 

8 


86 


THE   DISSECTOR. 


(corresponding  with  the  right  and  left  lobes  of  the  liver)  and  several 
smaller  apertures,  in  the  inferior  vena  cava. 

Summary. — The  liver  has  been  shown  to  be  composed  of  lobules ;  the 
lobules  (excepting  at  their  bases)  are  invested  and  connected  together, 
the  vessels  supported,  and  the  whole  organ  inclosed,  by  Glisson's  capsule; 
and  they  are  so  arranged,  that  the  base  of  every  lobule  in  the  liver  is  in 
contact  with  an  hepatic  vein  (sublobular) . 


THE  DISTRIBUTION  OF  THE  HEPATIC 
VEINS,  ACCORDING  TO  MR.  KlERNAN. 
FROM  MR.  KIERNAN'S  PAPER  IN  THE 
PHILOSOPHICAL  TRANSACTIONS  FOR 
1833. — 1.  A  section  of  a  sub-lobular 
vein.  2.  Longitudinal  sections  of  the 
lobules,  presenting  a  foliated  appear- 
ance. 3,  3.  Intra-lobular  veins.  4. 
"  The  bases  of  other  lobules  seen 
through  the  coats  of  the  vein,  and 
forming  the  canal  in  which  the  vein 
is  contained."  5.  The  openings  of 
intra-lobular  veins,  which  issue  from 
the  centre  of  the  base  of  each  lobule. 
6.  The  interlobular  fissures  separating 
the  bases  of  the  lobules. 


The  portal  vein  distributes  its  numberless  branches  through  portal 
canals,  which  are  channelled  through  every  part  of  the  organ ;  it  brings 
the  returning  blood  from  the  chylopoietic  viscera ;  it  collects  also  the  ve- 
nous blood  from  the  ultimate  ramifications  of  the  hepatic  artery  in  the 
liver  itself.  It  gives  off  branches  in  the  canals,  which  are  called  vaginal, 
and  form  a  venous  vaginal  plexus;  these  give  off  interlobular  branches, 
and  the  latter  enter  the  lobules  and  form  lobular  venous  plexuses,  from  the 
blood  circulating  in  which,  the  bile  is  secreted. 

The  bile  in  the  lobule  is  received  by  a  network  of  minute  ducts,  the 
lobular  biliary  plexus ;  it  is  conveyed  from  the  lobule  into  the  interlobu- 
lar ducts;  it  is  thence  poured  into  the  biliary  vaginal  plexus  of  the  portal 
canals,  and  thence  into  the  excreting  ducts,  by  which  it  is  carried  to  the 
duodenum  and  gall-bladder,  after  being  mingled  in  its  course  with  the 
mucous  secretion  from  the  numberless  muciparous  follicles  in  the  walls 
of  the  ducts. 

The  hepatic  artery  distributes  branches  through  every  portal  canal ; 
gives  off  vaginal  branches,  which  form  a  vaginal  hepatic  plexus,  from 
which  the  interlobular  branches  arise,  and  these  latter  terminate  ultimately 
in  the  lobular  venous  plexuses  of  the  portal  vein.  The  artery  ramifies 
abundantly  in  the  coats  of  the  hepatic  ducts,  enabling  them  to  provide 
their  mucous  secretion ;  and  supplies  the  vasa  vasorum  of  the  portal  and 
hepatic  veins,  and  the  nutrient  vessels  of  the  entire  organ. 

The  hepatic  veins  commence  in  the  centre  of  each  lobule  by  minute 
radicles,  which  collect  the  impure  blood  from  the  lobular  venous  plexus 
and  convey  it  into  the  intralobular  veins ;  these  open  into  the  sublobular 
veins,  and  the  sublobular  veins  unite  to  form  the  large  hepatic  trunks  by 
which  the  blood  is  conveyed  into  the  vena  cava. 

Physiological  and  pathological  Deductions. — The  physiological  deduction 
arising  out  of  this  anatomical  arrangement  is,  that  the  bile  is  wholly  se- 
creted from  venous  blood,  and  not  from  a  mixed  venous  and  arterial  blood, 


GALL-BLADDER.  87 

as  stated  by  Muller ;  for  although  the  portal  vein  receives  its  blood  from 
two  sources,  viz :  from  the  chylopoietic  viscera,  and  from  the  capillaries 
of  the  hepatic  artery,  yet  the  very  fact  of  the  blood  of  the  latter  vessel 
having  passed  through  its  capillaries  into  the  portal  vein,  or  in  extremely 
small  quantity  into  the  capillary  network  of  the  lobular  venous  plexus, 
is  sufficient  to  establish  its  venous  character.1 

The  pathological  deductions  depend  upon  the  following  facts  :  Each 
lobule  is  a  perfect  gland ;  of  uniform  structure,  of  uniform  color,  and  pos- 
sessing the  same  degree  of  vascularity  throughout.  It  is  the  seat  of  a 
double  venous  circulation,  the  vessels  of  the  one  (hepatic)  being  situated 
in  the  centre  of  the  lobule,  and  those  of  the  other  (portal)  in  the  cir- 
cumference. Now  the  color  of  the  lobule,  as  of  the  entire  liver,  depends 
chiefly  upon  the  proportion  of  blood  contained  within  these  two  sets  of 
vessels  ;  and  so  long  as  the  circulation  is  natural,  the  color  will  be  uni- 
form. But  the  instant  that  any  cause  is  developed  which  shall  interfere 
with  the  free  circulation  of  either,  there  will  be  an  immediate  diversity 
in  the  color  of  the  lobule. 

Thus,  if  there  be  any  impediment  to  the  free  circulation  of  the  venous 
blood  through  the  heart  or  lungs,  the  circulation  in  the  hepatic  veins 
will  be  retarded,  and  the  sublobular  and  the  intralobular  veins  will  be- 
come congested,  giving  rise  to  a  more  or  less  extensive  redness  in  the 
centre  of  each  of  the  lobules,  while  the  marginal  or  non-congested  por- 
tion presents  a  distinct  border  of  a  yellowish  white,  yellow,  or  green 
color,  according  to  the  quantity  and  quality  of  the  bile  it  may  contain. 
"  This  is  'passive  congestion'  of  the  liver,  the  usual  and  natural  state  of 
the  organ  after  death ;"  and,  as  it  commences  with  the  hepatic  vein,  it 
may  be  called  the  first  stage  of  hepatic  venous  congestion. 

But  if  the  causes  which  produced  this  state  of  congestion  continue,  or 
be  from  the  beginning  of  a  more  active  kind,  the  congestion  will  extend 
through  the  lobular  venous  plexuses  "  into  those  branches  of  the  portal 
vein  situated  in  the  interlobular  Jissures,  but  not  to  those  in  the  spaces, 
which,  being  larger,  and  giving  origin  to  those  in  the  fissures,  are  the  last 
to  be  congested."  In  this  second  stage  the. liver  has  a  mottled  appear- 
ance, the  non-congested  substance  is  arranged  in  isolated,  circular,  and 
ramose  patches,  in  the  centres  of  which  the  spaces  and  parts  of  the 
fissures  are  seen.  This  is  an  extended  degree  of  hepatic  venous  conges- 
tion ;  it  is  "  active  congestion"  of  the  liver,  and  very  commonly  attends 
disease  of  the  heart  and  lungs. 

These  are  instances  of  partial  congestion,  but  there  is  sometimes  general 
congestion  of  the  organ.  "In  general  congestion  the  whole  liver  is  of  a 
red  color,  but  the  central  portions  of  the  lobules  are  usually  of  a  deeper 
hue  than  the  marginal  portions." 

GALL-BLADDER. 

The  gall-bladder  is  the  reservoir  of  the  bile ;  it  is  a  pyriform 
sac,  situated  in  a  fossa  on  the  under  surface  of  the  right  lobe  of 
the  liver,  and  extending  from  the  right  extremity  of  the  trans- 
verse fissure  to  the  free  margin.  It  is  divided  into  a  body, 
fundus,  and  neck :  the  fundus  or  broad  extremity  in  the  natural 
position  of  the  liver  is  placed  downwards,  and  frequently  pro- 

1  For  arguments  on  this  contested  question,  see  the  article  LIVEB,  in 
the  "  Cyclopaedia  of  Anatomy  and  Physiology." 


88  THE   DISSECTOR. 

jects  beyond  the  free  margin  of  the  liver,  while  the  neck,  small 
and  constricted,  is  directed  upwards.  This  sac  is  composed  of 
three  coats,  serous,  fibrous  and  mucous.  The  serous  coat  is  par- 
tial, is  derived  from  the  peritoneum,  and  covers  that  side  only 
which  is  unattached  to  the  liver.  The  middle  or  jibrous  coat  is 
a  thin  but  strong  fibrous  layer,  connected  on  one  side  to  the 
liver,  and  on  the  other  to  the  peritoneum.  The  internal  or  mu- 
cous coat  is  but  loosely  attached  to  the  fibrous  layer;  it  is  every- 
where raised  into  minute  ruga?,  which  give  it  a  beautifully  reti- 
culated appearance,  and  forms,  at  the  neck  of  the  sac,  a  spiral 
valve.  It  is  continuous  through  the  hepatic  duct  with  the  mu- 
cous membrane  lining  all  the  ducts  of  the  liver,  and  through  the 
ductus  communis  choledochus  with  the  mucous  membrane  of  the 
alimentary  canal. 

The  Hilary  ducts  are,  the  hepatic,  cystic,  and  ductus  communis 
choledochus. 

The  hepatic  duct,  nearly  two  inches  long,  is  formed  in  the 
transverse  fissure  of  the  liver  by  the  junction  of  two  ducts  which 
proceed  from  the  right  and  left  lobes.  It  joins  the  cystic  duct 
at  an  acute  angle,  and  the  common  duct  resulting  from  their 
union  is  the  ductus  communis  choledochus. 

The  cystic  duct,  about  an  inch  in  length,  passes  inwards  from 
the  neck  of  the  gall-bladder,  and  unites  at  an  acute  angle  with 
the  preceding. 

The  ductus  communis  choledochus  descends  through  the  right 
border  of  the  lesser  omentum  to  the  duodenum  (page  76). 

The  coats  of  the  hepatic  duct  are  an  external  or  fibrous,  and  an  internal 
or  mucous  coat.  The  externnl  coat  is  composed  of  a  contractile  fibrous 
tissue,  which  is  probably  muscular ;  but  its  muscularity  has  not  yet  been 
demonstrated  in  the  human  subject.  The  mucous  coat  is  continuous  on 
the  one  hand  with  the  lining  membrane  of  the  hepatic  ducts  and  gall- 
bladder, and  on  the  other  with  that  of  the  duodenum. 

Vessels  and  Nerves. — The  gall-bladder  is  supplied  with  blood  by  the 
cystic  artery,  a  branch  of  the  hepatic.  Its  veins  return  their  blood  into 
the  portal  vein.  The  nerves  are  derived  from  the  hepatic  plexus. 

The  stomach  having  been  examined  in  situ,  may  now  be  removed,  after 
placing  a  ligature  around  the  cardiac  and  pyloric  orifices,  and  dividing 
the  extremity  of  the  oesophagus  on  the  one  hand,  and  the  commencement 
of  the  duodenum  on  the  other.  The  gastro-splenic  omentum  must  also 
be  divided,  and  any  other  connections  which  may  impede  the  observation 
of  the  parts  situated  behind  it.  The  duodenum  should  then  be  distended 
with  air,  and  the  student  may  proceed  to  examine  the  pancreas  with  the 
splenic  artery  and  vein  lying  on  its  upper  border,  the  superior  mesenteric 
artery  and  vein  and  portal  vein  issuing  from  behind  it,  and  the  spleen 
lying  at  its  small  extremity  and  connected  to  it  by  the  splenic  artery  and 


THE   PANCREAS.  89 


THE  PANCREAS. 

The  pancreas  is  a  long,  flattened,  conglomerate  gland,  analo- 
gous to  the  salivary  glands.     It  is  about  six  inches  in  length, 

Fig.  27. 


IN    THIS    FIGURE,    WHICH    IS    ALTERED    FROM    TlEDEMANN,    THE    LlVER    AN 

STOMACH  ARE  TURNED  UP,  TO  SHOW  THE  DUODENUM,  THE  PANCREAS,  AND  THE 
SPLEEN.  I.  The  under  surface  of  the  liver,  g.  Gall-bladder.  /.  The  com- 
mon bile-duct,  formed  by  the  union  of  a  duct  from  the  gall-bladder,  called  the 
cystic  duct,  and  of  the  hepatic  duct  coming  from  the  liver,  o.  The  cardiac  end 
of  the  stomach,  where  the  oesophagus  enters,  s.  Under  surface  of  the  stomach. 
p.  Pyloric  end  of  stomach,  d.  Duodenum,  h.  Head  of  pancreas ;  t,  tail;  and 
i,  body  of  that  gland.  The  substance  of  the  pancreas  is  removed  in  front,  to 
show  the  pancreatic  duct  (e)  and  its  branches,  r.  The  spleen,  v.  The  hilus, 
at  which  the  bloodvessels  enter,  c.  Crura  of  diaphragm,  n.  Superior  mesen- 
teric  artery,  a.  Aorta. 

and  between  three  and  four  ounces  in  weight ;  it  is  situated 
transversely  across  the  posterior  wall  of  the  abdomen,  behind  the 
stomach  ;  and  rests  on  the  aorta,  vena  port«,  inferior  vena  cava, 
the  origin  of  the  superior  mesenteric  artery,  and  the  left  kidney 
and  supra-renal  capsule ;  opposite  the  first  and  second  lumbar 
vertebras.  It  is  divided  into  a  body,  a  greater  and  a  smaller 
extremity :  the  great  end  or  head  is  placed  towards  the  right,  and 
is  surrounded  by  the  curve  of  the  duodenum  ;  the  lesser  end 
extends  to  the  left  as  far  as  the  spleen.  The  anterior  surface  of 
the  body  of  the  pancreas  is  covered  by  the  ascending  posterior 
layer  of  peritoneum,  and  is  in  relation  with  the  stomach,  the  first 
portion  of  the  duodenum,  and  the  commencement  of  the  trans- 
verse arch  of  the  colon.  The  posterior  surface  is  grooved  for  the 

8* 


90  THE   DISSECTOE. 

splenic  vein,  and  tunnelled  by  a  complete  canal  for  the  superior 
mesenteric  and  portal  vein,  and  superior  mesenteric  artery.  The 
upper  border  presents  a  deep  groove,  sometimes  a  canal,  for  the 
splenic  artery  and  vein,  and  is  in  relation  with  the  oblique  por- 
tion of  the  duodenum,  the  lobus  Spigelii,  and  coeliac  axis.  And 
the  lower  border  is  separated  from  the  transverse  portion  of  the 
duodenum  by  the  superior  mesenteric  artery  and  vein.  Upon 
the  posterior  part  of  the  head  of  the  pancreas  is  a  lobular  fold  of 
the  gland  which  completes  the  canal  of  the  superior  mesenteric 
vessels,  and  is  called  the  lesser  pancreas. 

In  structure,  the  pancreas  is  composed  of  reddish-yellow  polyhedral 
lobules  ;  these  consist  of  small  lobules,  and  the  latter  are  made  up  of  the 
arborescent  ramifications  of  minute  ducts,  terminating  in  csecal  pouches. 

The  pancreatic  duct  commences  at  the  small  extremity  of  the 
organ  by  two  branches,  which  converge  and  unite  after  a  course 
of  about  one-third  the  length  of  the  gland.  The  duct  is  then 
continued  onwards  from  left  to  right,  gradually  increasing  in 
size,  and  lying  nearer  the  anterior  than  the  posterior  surface  of 
the  organ,  to  the  lower  part  of  the  descending  duodenum,  where 
it  terminates  on  the  papilla  of  mucous  membrane,  common  to  it, 
and  the  ductus  communis  choledochus.  The  duct  receives  nume- 
rous branches  which  open  into  it  on  all  sides  from  the  lobules  of 
the  gland,  and  at  its  termination  is  slightly  dilated,  and  passes 
obliquely  between  the  muscular  and  mucous  coat  of  the  intestine 
to  reach  the  papilla.  The  duct  which  receives  the  secretion 
from  the  lesser  pancreas  is  called  the  ductus  pancreaticus  minor; 
it  opens  into  the  principal  duct  near  the  duodenum,  and  some- 
times passes  separately  into  that  intestine.  As  a  variety,  two 
pancreatic  ducts  are  occasionally  met  with. 

Vessels  and  Nerves. — The  arteries  of  the  pancreas  are  branches  of  the 
splenic,  hepatic,  and  superior  mesenteric  ;  the  veins  open  into  the  splenic 
vein  ;  the  lymphatics  terminate  in  the  lumbar  glands.  The  nerves. are 
filaments  of  the  splenic  plexus. 

THE  SPLEEN. 

The  spleen  (Fig.  21)  is  an  oblong  flattened  organ,  of  a  dark 
bluish-red  color,  situated  in  the  left  hypochondriac  region.  It  is 
variable  in  size  and  weight,1  spongy  and  vascular  in  texture,  and 
exceedingly  friable.  The  external  surface  is  convex,  the  internal 
slightly  concave,  indented  along  the  middle  line,  and  pierced  by 
several  large  and  irregular  openings  for  the  entrance  and  exit  of 
vessels  ;  this  is  the  hilum  lienis.  The  upper  extremity  is  somewhat 
larger  than  the  lower,  and  rounded  ;  the  inferior  is  flattened ;  the 
posterior  border  is  obtuse,  the  anterior  sharp,  and  marked  by 

1  Its  ordinary  length  is  about  five  inches ;  and  its  weight,  six  ounces. 


THE   SUPRA-RENAL   CAPSULES.  91 

several  notches.  The  spleen  is  in  relation  by  its  external  or  con- 
vex surface  with  the  diaphragm,  which  separates  it  from  the  ninth, 
tenth,  and  eleventh  ribs ;  by  its  concave  surface,  with  the  great 
end  of  the  stomach,  the  extremity  of  the  pancreas,  the  gastro- 
splenic  omentum  and  its  vessels,  the  left  kidney  and  supra-renal 
capsule,  and  the  left  crus  of  the  diaphragm  ;  by  its  upper  end  with 
the  diaphragm,  and  sometimes  with  the  extremity  of  the  left  lobe 
of  the  liver ;  and,  by  its  lower  end,  with  the  left  extremity  of  the 
transverse  arch  of  the  colon.  It  is  connected  to  the  stomach  by 
the  gastro-splenic  omentum,  and  to  the  diaphragm  by  a  fold  of 
the  peritoneum  called  the  suspensory  ligament. 

A  second  spleen  (lien  succenturiatus)  is  sometimes  found  appended  to 
one  of  the  branches  of  the  splenic  artery,  near  the  great  end  of  the  sto- 
mach ;  when  it  exists,  it  is  round  and  of  small  size,  rarely  larger  than  a 
hazel-nut.  I  have  seen  two,  and  even  three  of  these  bodies ;  there  may 
be  more. 

The  spleen  is  invested  by  the  peritoneum  and  by  a  tunica  propria  of 
elastic  tissue,  which  enables  it  to  yield  to  the  greater  or  less  distension 
of  its  vessels.  The  elastic  tunic  forms  sheaths  for  the  vessels  in  their 
ramifications  through  the  organ,  and  from  these  sheaths  small  fibrous 
bands  (train-cube)  are  given  off  in  all  directions,  which  become  attached 
to  the  internal  surface  of  the  elastic  tunic,  and  constitute  the  areolar 
framework  of  the  spleen.  The  substance  occupying  the  interspaces  of 
this  tissue  is  soft,  granular,  and  of  a  bright  red  color,  interspersed  with 
small,  white,  soft  corpuscles  (Malpighian  bodies).  These  corpuscles,  ac- 
cording to  the  researches  of  Oesterlen  and  Simon,  are  aggregations  of 
c\  toblasts  inclosed  in  a  kind  of  capsule  of  capillary  vessels.  There  are, 
besides,  separate  cytoblasts  abundantly  scattered  through  the  red  sub- 
stance. 

Vessels  and  Nerves. — The  splenic  artery  is  of  very  large  size  in  proportion 
to  the  bulk  of  the  spleen  ;  it  is  a  division  of  the  coeliac  axis.  The  branches 
which  enter  the  spleen  are  distributed  to  distinct  sections  of  the  organ, 
and  anastomose  very  sparingly  with  each  other.  The  veins,  by  their 
numerous  dilatations,  constitute  the  principal  part  of  the  bulk  of  the 
spleen  ;  they  pour  their  blood  into  the  splenic  vein,  which  is  one  of  the 
two  great  formative  trunks  of  the  portal  vein.  The  lymphatics  are  re- 
markable for  their  number  and  large  size  ;  they  terminate  in  the  lumbar 
glands.  The  nerves  are,  the  splenic  plexus,  derived  from  the  solar  plexus. 

THE  SUPRA-RENAL  CAPSULES. 

The  supra-renal  capsules  are  two  small  yellowish  and  flattened 
bodies  surmounting  the  kidneys,  and  inclining  inwards  towards 
the  vertebral  column.  The  right  is  somewhat  three-cornered  in 
shape,  the  left  semilunar;  they  are  connected  to  the  kidneys  by 
the  common  investing  cellular  tissue,  and  each  capsule  is  marked 
on  its  anterior  surface  by  a  fissure  which  appears  to  divide  it  into 
two  lobes.  The  right  supra-renal  capsule  is  closely  adherent  to 
the  posterior  and  under  surface  of  the  liver,  the  left  lies  in  contact 
with  the  pancreas  and  spleen.  Both  capsules  rest  agaiust  the 


92  THE   DISSECTOR. 

crura  of  the  diaphragm  on  a  level  with  the  tenth  dorsal  vertebra, 
and,  by  their  inner  border,  are  in  relation  with  the  great  splanchnic 
nerve  and  semilunar  ganglion.  They  are  larger  in  the  foetus  than 
in  the  adult,  and  appear  to  perform  some  office  connected  with 
embryonic  life.  The  anatomy  of  these  organs  in  the  foetus  will 
be  found  in  a  subsequent  chapter. 

In  structure  they  are  composed  of  two  substances,  cortical  and  medul- 
lary. The  cortical  substance  is  of  a  yellowish  color,  and  consists  of  straight 
parallel  columns  placed  perpendicularly  side  by  side.  The  medullary 
substance  is  generally  of  a  dark  brown  color,  double  the  quantity  of  the 
yellow  substance,  soft  and  spongy  in  texture,  and  contains  within  its 
centre  the  trunk  of  a  large  vein,  the  vena  supra-renalis.  It  is  the  large 
size  of  this  vein  that  gives  to  the  fresh  supra-renal  capsule  the  appearance 
of  a  central  cavity :  the  dark-colored  pulpy  or  fluid  contents  of  the  cap- 
sule, at  a  certain  period  after  death,  are  produced  by  softening  of  the 
medullary  substance.  Dr.  Nagel1  has  shown,  by  his  injections  and  mi- 
croscopic examinations,  that  the  appearance  of  columns  in  the  cortical 
substance  is  caused  by  the  direction  of  a  plexus  of  capillary  vessels.  Of 
the  numerous  minute  arteries,  supplying  the  supra-renal  capsule,  he  says, 
the  greater  number  enter  the  cortical  substance  at  every  point  of  its  sur- 
face, and,  after  proceeding  for  scarcely  half  a  line,  divide  into  a  plexus 
of  straight  capillary  vessels.  Some  few  of  the  small  arteries  traverse  the 
cortical  layer,  and  give  off,  in  the  medullary  substance,  several  branches 
which  proceed  in  different  directions,  and  re-enter  the  cortical  layer,  to 
divide  into  a  capillary  plexus  in  a  similar  manner  with  the  first  described. 
From  the  capillary  plexus,  composing  the  cortical  layer,  the  blood  is  re- 
ceived by  numerous  small  veins,  which  form  a  venous  plexus  in  the 
medullary  substance,  and  terminate  at  acute  angles  in  the  large  central 
vein. 

According  to  the  more  recent  researches  of  Oesterlen  and  Simon,  the 
appearance  of  columns  is  due  to  groups  of  small  corpuscles  or  cytoblasts 
associated  with  elementary  granules  and  fat-cells  collected  together  in 
the  form  of  parallel  cylinders  or  cones,  each  group  being  inclosed  in  a 
tube  of  delicate  membrane  (limitary  membrane).  The  medullary  sub- 
stance and  intercolumnar  spaces  contain  cytoblasts  uniformly  scattered 
and  interspersed  with  granules  and  fat-cells.  Oesterlen  found  also,  occa- 
sionally, in  the  medullary  substance,  elongated  spaces  without  lining 
membrane  containing  a  thick  grayish-white  fluid. 

Vessels  and  Nerves. — The  supra-renal  arteries  are  derived  from  the 
aorta,  from  the  renal,  and  from  the  phrenic  arteries  ;  they  are  remarkable 
for  the  innumerable  minute  twigs  into  which  they  divide,  previously  to 
entering  the  capsule.  The  supra-renal  vein  collecting  the  blood  from  the 
medullary  venous  plexus,  and  receiving  several  branches  which  pierce 
the  cortical  layer,  opens  directly  into  the  vena  cava  on  the  right  side,  and 
into  the  renal  vein  on  the  left. 

The  lymphatics  are  large  and  very  numerous ;  they  terminate  in  the 
lumbar  glands.  The  nerves  are  derived  from  the  renal  and  from  the 
phrenic  plexus. 

1  Miiller's  Archiv.,  1836. 


THE   KIDNEYS. 


93 


THE   KIDNEYS. 

The  kidneys,  the  secreting  organs  of  the  urine,  are  situated  in 
the  lumbar  regions,  behind  the  peritoneum,  and  on  each  side  of  the 
vertebral  column,  extending  from 
the  eleventh  rib  to  near  the  crest  g* 

of  the  ilium,  and  approaching  the 
vertebral  column  by  their  upper 
ends.  Each  kidney  is  between 
four  and  five  inches  in  length, 
about  two  inches  and  a  half  in 
breadth,  somewhat  more  than  one 
inch  in  thickness,  and  weighs  be- 
tween three  and  four  ounces.  The 
kidneys  are  usually  surrounded  by 
fat ;  they  rest  on  the  crura  of  the 
diaphragm,  on  the  anterior  lamella 
of  the  aponeurosis  of  the  trans- 
versalis  muscle,  which  separates 
them  from  the  quadratus  lum- 
borum,  and  on  the  psoas  magnus. 
The  right  kidney  is  somewhat 
lower  than  the  left,  from  the  posi- 
tion of  the  liver;  it  is  in  relation, 
by  its  anterior  surface,  with  the 
liver  and  descending  portion  of 
the  duodenum,  which  rest  against 


A  SECTION  OF  THE  KIDNEY,  STTK- 
MOUNTED  BY  THE  SUPRA-RENAL 
CAPSULE  ;  THE  SWELLINGS  UPON 
THE  SURFACE  MARK  THE  ORIGINAL 


it ;  and  is  covered  in  by  the  as- 


nal capsule.  2.  The  vascular  por- 
tion of  the  kidney.  3,  3.  Its  tubular 
portion,  consisting  of  cones.  4,  4. 
Two  of  the  papillae  projecting  into 
thin  corresponding  calices.  5,  5,  5. 
The  three  infundibula ;  the  middle 


cending  colon.  The  left  kidney, 
higher  than  the  right,  is  covered, 
in  front,  by  the  great  end  of  the 
stomach,  by  the  spleen  and  de- 
scending colon.  The  anterior  sur- 
face of  the  kidney  is  convex,  while  the  posterior  is  flat ;  the  su- 
perior extremity  is  in  relation  with  the  supra-renal  capsule;  the 
convex  border  is  turned  outwards  towards  the  parietes  of  the  ab- 
domen; the  concave  border  looks  inwards  towards  the  vertebral 
column,  and  presents  a  deep  notch  (hilum  renale),  which  leads 
to  a  cavity,  or  sinus,  within  the  organ.  In  the  sinus  renalis  are 
situated  the  vessels  and  nerves  of  the  kidney,  and  the  expansion 
of  the  excretory  duct  called  pelvis  renalis.  At  the  hilum  these 
vessels  are  so  placed  that  the  renal  vein  is  in  front  of  the  artery, 
and  the  pelvis  and  ureter  behind. 

The  kidney  is  dense  and  fragile  in  texture,  and  invested  by  a  proper 
fibrous  capsule,  which  is  easily  torn  from  its  surface.  When  divided  by 
a  longitudinal  incision,  carried  from  the  convex  to  the  concave  border, 


94  THE   DISSECTOR. 

it  is  found  to  present  in  its  interior  two  structures,  an  external  or  vascu- 
lar (cortical),  and  an  internal  or  tubular  (medullary)  substance.  The 
tubular  portion  is  formed  of  pale  reddish-colored  conical  masses,  corre- 
sponding by  their  bases  with  the  vascular  structure,  and  by  their  apices 
with  the  hilum  of  the  organ ;  these  bodies  are  named  cones  (pyramids  of 
Malpighi),  and  are  from  eight  to  fifteen  in  number.  The  vascular  portion, 
about  two  lines  in  thickness,  is  composed  of  bloodvessels  and  the  plexi- 
form  convolutions  of  uriniferous  tubuli,  and  not  only  constitutes  the  sur- 
face of  the  kidney,  but  dips  between  the  cones  and  surrounds  them  nearly 
to  their  apices  (septula  renmn). 

The  cones  or  pyramids  of  the  tubular  portion  of  the  kidney  are  com- 
posed of  minute  straight  tubuli  uriniferi,  of  about  the  diameter  of  a  fine 
hair.  The  tubuli  commence  at  the  apices  of  the  cones,  and  pursue  a  pa- 
rallel course  towards  the  periphery  of  the  organ,  bifurcating  from  point 
to  point,  and  separated  only  by  minute  straight  bloodvessels,  and  a  small 
quantity  of  parenchymatous  substance.  At  the  bases  of  the  pyramids 
the  tubuli  collect  into  smaller  conical  fasciculi  (pyramids  of  Ferrein), 
which  are  prolonged  into  the  substance  of  the  cortical  portion  of  the  kid- 
ney, and  have  interposed  between  them  processes  of  the  vascular  struc- 
ture. In  the  smaller  pyramids  the  fasciculi  separate  into  their  component 
tubules,  which,  after  a  course  marked  by  "  tortuosities,  plexuses,  convo- 
lutions, and  dilatations,"  terminate,  according  to  Mr.  Bowman,'  in  small 
round  bodies,  the  corpora  Malpighiana,  or,  according  to  Krause,  and  the 
recent  investigations  of  Mr.  Toynbee,2  by  anastomoses  and  caecal  extre- 
mities. The  average  diameter  of  the  tubuli  uriniferi  in  the  cortical  por- 
tion of  the  kidney  is  l-480th  of  an  inch,  of  which  about  two-thirds  are 
occupied  by  a  nucleated  epithelium,  the  remaining  third  representing  the 
area  of  the  tube.  According  to  Mr.  Bowman,  the  epithelium  is  ciliated 
in  that  part  of  the  tubule  which  is  near  the  Malpighian  body,  the  tubule 
itself  being  very  much  constricted. 

In  the  cortical  portion  of  the  kidney  are  contained  a  multitude  of 
minute,  red,  globular  bodies,  the  corpora  Malpighiana,  or  glomeruli. 
Each  Malpighian  body,  about  l-100th  of  an  inch  in  diameter,  is  com- 
posed of  a  plexus  of  capillary  vessels,  and  in  addition,  according  to  Mr. 
Toynbee,  of  a  coil  of  an  uriniferous  tubule ;  the  tuft  of  capillaries  and  the 
coil  of  the  tubule  being  both  inclosed  in  a  thin  membranous  capsule. 
According  to  Mr.  Bowman,  the  capsule  of  the  Malpighian  body  is  the 
origin  of  the  uriniferous  tubule  expanded  into  a  globular  form  for  the 
reception  of  the  capillary  tuft.  The  capillary  vessels  of  the  vascular  tuft 
are  arranged  in  loops  closely  packed  together,  and  surrounded  by  an 
epithelium,  which  is  continuous  with  a  similar  structure  lining  the  inner 
surface  of  the  capsule.  They  are  derived  from  a  small  artery,  which, 
after  piercing  the  capsule,  immediately  divides  in  a  radiated  manner  into 
several  branches.  From  the  interior  of  this  little  vascular  ball  a  vein 
proceeds,  smaller  than  the  corresponding  artery,  and  pierces  the  capsule 
close  by  the  artery,  to  communicate  with  the  efferent  vessels  of  other 
Malpighian  bodies  and  constitute  a  venous  plexus. 

The  cones  or  mamillary  processes  of  the  interior  of  the  kidney  are  in- 
vested by  mucous  membrane,  which  is  continuous  at  their  apices  with 


1  On  the  Structure  and  Use  of  the  Malpighian  Bodies  of  the  Kidney. 
Philosophical  Transactions,  1842. 

2  On  the  intimate  Structure  of  the  Human  Kidney,  &n,     Medico-Chi- 
rurgical  Transactions,  vol.  xxix.  1846. 


THE   URETER.  95 

the  uriniferous  tubuli,  and  is  reflected  from  their  sides  so  as  to  form 
around  each  a  cup-like  pouch,  or  calyx.  The  calices  communicate  with 
a  common  cavity  of  larger  size,  situated  at  each  extremity,  and  in  the 
middle  of  the  organ;  and  these  three  cavities,  the  infundibula,  constitute 
by  their  union  the  large  membranous  sac,  which  emerges  through  the 
hilum  renale,  the  pelvis  of  the  kidney. 

The  kidney  in  the  embryo  and  foetus  consists  of  lobules.  See  the  ana- 
tomy of  the  foetus  in  a  succeeding  chapter. 

The  ureter  (ovpov,  urine,  t^riv,  to  keep),  the  excretory  duct  of 
the  kidney,  is  a  membranous  tube  of  about  the  diameter  of  a 
goose-quill,  and  nearly  eighteen  inches  in  length;  it  is  con- 
tinuous, superiorly,  with  the  pelvis  of  the  kidney,  and  is  con- 
stricted inferiorly,  where  it  lies  in  an  oblique  direction  between 
the  muscular  and  mucous  coat  of  the  base  of  the  bladder,  and 
opens  upon  its  mucous  surface.  Lying  along  the  posterior  wall 
of  the  abdomen,  it  is  situated  behind  the  peritoneum,  and  is 
crossed  by  the  spermatic  vessels;  in  its  course  downwards  it  rests 
against  the  anterior  surface  of  the  psoas,  and  crosses  the  com- 
mon iliac  artery  and.  vein,  and  then  the  external  iliac  vessels. 
Within  the  pelvis  it  crosses  the  hypogastric  cord  and  vas  deferens 
in  the  male,  and  runs  by  the  side  of  the  cervix  uteri  and  upper 
part  of  the  vagina  in  the  female.  There  are  sometimes  two 
ureters  to  one  kidney.  The  ureter,  the  pelvis,  the  infundibula, 
and  the  calices  are  composed  of  two  coats,  an  external  or  fibro- 
cellular  coat,  the  tunica  propria,  and  an  internal  mucous  coat, 
which  is  continuous  with  the  mucous  membrane  of  the  bladder 
inferierly,  and  with  that  of  the  tubuli  uriniferi  above.  The  cells 
of  the  epithelium  are  spheroidal. 

Vessels  and  Nerves. — The  renal  artery  is  derived  from  the  aorta ;  it 
divides  into  several  large  branches  before  entering  the  hilum,  and  within 
the  organ  ramifies  in  an  arborescent  manner,  terminating  in  nutrient 
twigs,  and  the  small  inferent  vessels  of  the  corpora  Malpighiana.  In  the 
Malpighian  bodies  the  inferent  vessels  divide  into  several  primary  twigs, 
which  subdivide  into  capillaries,  and  the  capillaries,  after  forming  loops, 
converge  to  the  efferent  vein,  which  is  generally  smaller  than  the  corre- 
sponding artery.  The  efferent  veins  proceed  to,  and  form  a  capillary 
venous  plexus,  which  surrounds  the  tortuous  tubuli  uriniferi,  and  from 
this  venous  plexus  the  blood  is  conveyed,  by  converging  branches,  into 
the  renal  vein. 

"Thus,"  remarks  Mr.  Bowman,  "there  are  in  the  kidrtey  two  perfectly 
distinct  systems  of  capillary  vessels,  through  both  of  which  the  blood 
passes  in  its  course  from  the  arteries  into  the  veins ;  the  first,  that " 
which  forms  the  vascular  tuft  in  the  Malpighian  bodies,  and  is  "in  im- 
mediate connection  with  the  arteries ;  the  second,  that  enveloping  the 
convolutions  of  the  tubes,  and  communicating  directly  with  the  veins. 
The  efferent  vessels  of  the  Malpighian  bodies,  that  carry  the  blood  be- 
tween these  two  systems,  may  collectively  be  termed  the  portal  system 
of  the  kidney."  The  inferences  drawn  by  Mr.  Bowman  from  his  inves- 
tigations are  interesting ;  they  are,  that  the  capillary  tufts  of  the  Mal- 
pighiau  bodies  are  the  part  of  the  kidney  specially  acted  on  by  diuretics ; 


96  THE   DISSECTOR. 

that  they  are  the  medium  by  which  water,  certain  salts,  and  other  sub- 
stances, pass  out  of  the  system ;  that  they  are,  moreover,  the  means  of 
escape  of  certain  morbid  products,  such  as  sugar,  albumen,  and  the  red 
particles  of  the  blood.  Respecting  the  capillary  venous  plexus,  we  have 
proof  that  the  principal  proximate  constituents  of  urine,  such  as  urea, 
lithic  acid,  &o.,  are,  like  the  bile,  derived  from  venous  (portal)  blood. 

The  veins  of  the  kidney  commence  at  the  surface  by  minute  con- 
verging venules,  the  stellated  vessels,  and  proceed  inwards,  receiving  in 
their  course  the  veins  of  the  cortical  and  tabular  portions  of  the  organ. 
On  arriving  at  the  pelvis,  they  unite  to  form  the  branches  of  the  renal 
vein,  which  terminates  in  the  vena  cava  by  a  single  large  trunk  on  each 
side ;  the  left  renal  vein  receiving  the  left  spermatic  vein.  Injections 
thrown  into  the  renal  artery,  and  returning  by  the  tubuli  uriniferi,  make 
their  way  into  those  tubes  by  rupture.  The  lymphatic  vessels  terminate 
in  the  lumbar  glands. 

The  nerves  are  derived  from  the  renal  plexus,  which  is  formed  partly 
by  the  solar  plexus,  and  partly  by  the  lesser  splanchnic  nerve.  The 
renal  plexus  gives  branches  to  the  spermatic  plexus,  and  branches  which 
accompany  the  ureters :  hence  the  morbid  sympathies  which  exist  .be- 
tween the  kidney,  the  ureter,  and  the  testicle ;  and  by  the  communica- 
tions with  the  solar  plexus,  with  the  stomach  and  diaphragm,  and  indeed 
with  the  whole  system.  In  the  intimate  structure  of  the  kidney,  the 
nerve-fibres  are,  according  to  Mr.  Toynbee,  continuous  with  the  nucleated 
cells  of  the  parenchyma  of  the  organ. 

DEEP  VESSELS  AND  -NERVES  OF  THE  ABDOMEN. 

The  deep  vessels  and  nerves  of  the  abdomen  are  the  abdominal 
aorta,  inferior  vena  cava,  thoracic  duct,  and  sympathetic  nerve. 

The  duodenum  and  pancreas  may  now  be  removed,  together  with  any 
cellular  tissue,  membrane,  or  organ  which  may  impede  the  view  of  the 
great  vessels  lying  upon  the  vertebral  column.  In  following  the  branches 
of  the  arteries  and  veins,  care  should  be  taken  to  avoid  destroying  the 
nerves  which  lie  upon  the  vessels  and  their  numerous  plexuses. 

The  ABDOMINAL  AORTA  enters  the  abdomen  through  the  aortic 
opening  of  the  diaphragm,  and  between  the  two  pillars  of  that 
muscle.  In  its  course  downwards,  it  lies  on  the  left  of  the  ver- 
tebral column,  and  terminates  on  the  fourth  lumbar  vertebra  by 
dividing  into  the  two  common  iliac  arteries.  It  is  crossed  by 
the  left  renal  vein,  pancreas,  transverse  duodenum,  and  mesen- 
tery, and  is  in  relation  behind  with  the  thoracic  duct,  recepta- 
culum  chyli,  and  left  lumbar  veins.  On  its  left  side  is  situated 
the  left  semilunar  ganglion  and  sympathetic  nerve,  and  on  its 
right,  the  inferior  vena  cava,  right  semilunar  ganglion,  and  the 
commencement  of  the  vena  azygos. 

The  branches  of  the  abdominal  aorta  are,  the — 
Phrenic,  Spermatic, 

(  Gastric,  Inferior  mesenteric, 

Cceliac  axis  -I  Hepatic,  Supra-renal, 

(^  Splenic,  Renal, 

Superior  mesenteric,  Lumbar, 

Sacra  media. 


PHRENIC   ARTERIE*S. 


Fig.  29. 


The  PHRENIC  ARTERIES  are  given  off  (frequently  by  a  common 
trunk),  from  the  anterior  part  of  the  aorta,  as  soon  as  that  vessel 
has  passed  through  the  aortic  opening.  Passing  obliquely  out- 
wards upon  the  under  surface  of  the  diaphragm,  each  artery 
divides  into  two  branches:  an  internal  branch,  which  runs  for- 
ward and  inosculates  with  its  fellow  of  the  opposite  side  in  front 
of  the  cesophageal  opening;  and  an  external  branch,  which 
proceeds  outwards  to- 
wards the  great  circum- 
ference of  the  muscle, 
and  sends  branches  to 
the  supra- renal  cap- 
sules. The  phrenic  ar- 
teries inosculate  with 
branches  of  the  internal 
mammary,  intercostal, 
epigastric,  cesophageal, 
gastric,  hepatic,  and  su- 
pra-renal arteries.  They 
are  not  unfrequently  de- 
rived from  the  cceliac 
axis,  or  from  one  of  its 
divisions  ;  and  some- 
times they  give  off  the 
supra-renal  arteries. 

The  COSLIAC  AXIS  is 
so  named  from  giving 
off  the  three  large  ar- 
teries, gastric,  hepatic, 
and  splenic,  which  pass 
off  from  its  summit  as 
from  a  centre.  The 
trunk  of  the  coeliac  axis 
is  surrounded  by  a  plex- 
us of  nerves,  which  has 
received  the  name  of 
solar  plexus ;  and  in 
the  substance  of  the 

THE  ABDOMINAL  AORTA  WITH  ITS  BRANCHES. — 1.  The  phrenic  arteries.  2. 
The  coeliac  axis.  3.  The  gastric  artery.  4.  The  hepatic  artery,  dividing  into 
the  right  and  left  hepatic  branches.  5.  The  splenic  artery,  passing  outwards 
to  the  spleen.  6.  The  supra-renal  artery  of  the  right  side.  7.  The  right  renal 
artery,  which  is  longer  than  the  left,  passing  outwards  to  the  right  kidney.  8. 
The  lumbar  arteries.  9.  The  superior  mesenteric  artery.  10.  The  two  sper- 
matic arteries.  11.  The  inferior  mesenteric  artery.  12.  The  sacra  media.  13. 
The  common  iliacs.  14.  The  internal  iliac  of  the  right  side.  15.  The  exter- 
nal iliac  artery.  16.  The  epigastric  artery.  17.  The  circumflexa  ilii  artery. 
18.  The  femoral  artery. 

9 


98  THE   DISSECTOR. 

solar  plexus  on  each  side  is  the  semilnnar  ganglion.     The  ar- 
tery cannot  be  cleaned  without  destroying  these  nerves. 

The  branches  of  the  coeliac  axis  have  been  already  described  (page  73)  ; 
as  have  the  superior  and  inferior  inesenteric  arteries  (pages  69,  71). 

The  SPERMATIC  ARTERIES  are  two  small  vessels  which  arise  from 
the  front  of  the  aorta,  below  the  superior  mesenteric.  From  this 
origin  each  artery  passes  obliquely  outwards,  and  accompanies 
the  corresponding  ureter  along  the  front  of  the  psoas  muscle  to 
the  border  of  the  pelvis,  where  it  is  in  relation  with  the  external 
iliac  artery.  It  is  then  directed  outwards  to  the  internal  abdo- 
minal ring,  and  follows  the  course  of  the  spermatic  cord,  along 
the  spermatic  canal  and  through  the  scrotum  to  the  testicle,  to 
which  it  is  distributed.  The  right  spermatic  artery  lies  in  front 
of  the  vena  cava ;  and  both  vessels  are  accompanied  by  their  cor- 
responding veins  and  by  the  spermatic  plexuses  of  nerves. 

The  spermatic  arteries  in  the  female  (ovarian)  descend  into 
the  pelvis,  and  pass  between  the  two  layers  of  the  broad  ligaments 
of  the  uterus,  to  be  distributed  to  the  ovaries,  Fallopian  tubes, 
and  round  ligaments.  Along  the  latter  they  are  continued  to 
the  inguinal  canal  and  labium  at  each  side.  They  inosculate 
with  the  uterine  arteries. 

The  SUPRA-RENAL  ARTERIES  (capsular)  are  two  small  vessels 
which  arise  from  the  aorta  immediately  above  the  renal  arteries, 
and  are  distributed  to  the  supra-renal  capsules.  They  are  some- 
times branches  of  the  phrenic  or  of  the  renal  arteries. 

The  RENAL  ARTERIES  (emulgent)  are  two  large  trunks  given 
off  from  the  sides  of  the  aorta,  immediately  below  the  superior 
mesenteric  artery.  The  right  is  longer  than  the  left,  on  account 
of  the  position  of  the  aorta,  and  passes  behind  the  vena  cava  to 
the  kidney  of  that  side.  The  left  is  somewhat  higher  than  the 
right.  They  divide  into  several  large  branches  previously  to 
entering  the  kidney,  and  ramify  very  minutely  in  its  vascular 
portion.  The  renal  arteries  supply  several  small  branches  to  the 
supra-renal  capsules,  and  one  to  the  ureter. 

The  LUMBAR  ARTERIES  correspond  with  the  intercostals  in  the 
chest.  They  are  four  or  five  in  number  on  each  side,  curve  around 
the  bodies  of  the  lumbar  vertebrae  beneath  the  psoas  muscles,  and 
divide  into  two  branches  ;  one  of  which  passes  backwards  between 
the  transverse  processes,  and  is  distributed  to  the  vertebrae,  spinal 
cord  and  muscles  of  the  back,  whilst  the  other,  taking  its  course 
behind  the  quadratus  lumborum,  supplies  the  abdominal  muscles, 
and  inosculates  with  branches  of  the  internal  mammary  and  epi- 
gastric arteries.  The  first  lumbar  artery  runs  along  the  lower 
border  of  the  last  rib ;  and  the  last,  along  the  crest  of  the  ilium. 
In  passing  between  the  psoas  muscle  and  the  vertebrae,  they  are 
protected  by  a  series  of  tendinous  arches,  which  defend  them  and 


EXTERNAL  ILIAC  ARTERY.  99 

the  communicating  branches  of  the  sympathetic  nerve  from  pres- 
sure during  the  action  of  the  muscle. 

The  SACRA  MEDIA  arises  from  the  posterior  part  of  the  aorta 
at  its  bifurcation,  and  descends  along  the  middle  of  the  anterior 
surface  of  the  sacrum  to  the  first  piece  of  the  coccyx,  where  it 
terminates  by  inosculating  with  the  lateral  sacral  arteries.  It 
distributes  branches  to  the  rectum  and  anterior  sacral  nerves,  and 
inosculates  on  each  side  with  the  lateral  sacral  arteries. 

Varieties  in  the  Branches  of  the  Abdominal  Aorta. — The  phrenic  arteries 
are  very  rarely  botli  derived  from  the  aorta.  One  or  both  may  be  branches 
of  the  cceliac  axis  ;  one  may  proceed  from  the  gastric  artery,  from  the  renal, 
or  from  the  upper  lumbar  artery.  There  are  occasionally  three  or  more 
phrenic  arteries.  The  cceliac  axis  is  very  variable  in  length,  and  gives 
off  its  branches  irregularly.  There  are  sometimes  two  or  even  three  he- 
patic arteries,  one  of  which  may  be  derived  from  the  gastric  or  even  from 
the  superior  mesenteric. 

The  colica  media  is  sometimes  derived  from  the  hepatic  artery.  The 
spermatic  arteries  are  very  variable  both  in  origin  and  number.  The  right 
spermatic  may  be  a  branch  of  the  renal  artery,  and  the  left  a  branch  of 
the  inferior  mesenteric.  The  supra-renal  arteries  may  be  derived  from 
the  phrenic  or  renal  arteries.  The  renal  arteries  present  several  varieties 
in  number  ;  there  may  be  three  or  even  four  arteries  on  one  side,  and  one 
only  on  the  other.  When  there  are  several  renal  arteries  on  one  side, 
one  may  arise  from  the  common  iliac  artery,  from  the  front  of  the  aorta 
near  its  lower  part,  or  from  the  internal  iliac. ' 

COMMON  ILIAC  ARTERIES. — The  bifurcation  of  the  aorta  usually 
takes  place  on  the  fourth  lumbar  vertebra.  Sometimes  it  occurs 
as  high  as  the  third,  and  occasionally  as  low  as  the  fifth.  The 
common  iliac  arteries  are  about  two  inches  in  length.  They  di- 
verge from  the  termination  of  the  aorta,  and  pass  downwards  and 
outwards  on  each  side  to  the  margin  of  the  pelvis  opposite  the 
sacro-iliac  symphysis,  where  they  divide  into  the  external  and 
internal  iliac  arteries.  In  old  persons,  the  common  iliacs  are  more 
or  less  dilated  and  curved  in  their  course. 

The  right  artery  is  somewhat  longer  than  the  left,  and  forms  a 
more  obtuse  angle  with  the  termination  of  the  aorta.  The  angle 
of  bifurcation  is  greater  in  the  female  than  in  the  male. 

Both  arteries  are  covered  by  peritoneum,  and  are  crossed  at 
their  point  of  bifurcation  by  the  ureter.  The  left  is  furthermore 
crossed  by  the  rectum  and  superior  hemorrhoidal  artery.  Both 
are  in  relation,  externally,  with  thepsoas  muscle,  and  behind  with 
the  common  iliac  vein,  the  right  artery  being  also  in  relation  with 
the  left  common  iliac  vein,  which  crosses  behind  it,  to  terminate 
in  the  inferior  vena  cava. 

The  EXTERNAL  ILIAC  ARTERY  passes  obliquely  downwards  along 
the  inner  border  of  the  psoas  muscle,  from  opposite  the  sacro- 
iliac  symphysis  to  the  femoral  arch,  whereat  becomes  the  femoral 
artery.  It  is  covered  in  by  the  peritoneum  and  by  a  thin  layer  of 


100 


THE  DISSECTOR. 


fascia  derived  from  the  iliac  fascia,  has  lying  upon  it  the  spermatic 
vessels,  and  is  crossed  near  its  termination  hy  the  crural  branch 
of  the  genito-crural  nerve,  and  by  the  circumflexa  ilii  vein.  Ex- 
ternally it  is  in  relation  with  the  psoas  muscle,  the  iliac  fascia 
being  interposed  ;  and  posteriorly  it  has  the  external  iliac  vein, 
which  at  Poupart's  ligament  is  placed  to  its  inner  side.  The 

artery  is  surrounded  by  lymphatic 
Fig.  30.  vessels  and  several  lymphatic  glands. 

The  branches  of  the  external  iliac 
artery  are  two  or  three  small  twigs 
to  the  psoas  muscle  and  lymphatic 
glands,  the  epigastric  and  circum- 
flexa ilii  artery;  the  two  latter  are 
given  off  close  to  Poupart's  liga- 
ment. 

The  epigastric  artery  may  now  be  seen 
taking  its  course  beneath  the  peritoneum 
to  the  sheath  of  the  rectus,  and  forming 
the  prominence  of  the  internal  wall  of 
the  abdomen,  which  determines  the  po- 
sition of  the  two  fossae  through  which 
the  two  forms  of  inguinal  hernia  proceed. 
The  relation  of  the  artery  to  the  two  ab- 
dominal rings,  internal  and  external, 
should  be  noted,  and  also  its  relation  to 
the  femoral  ring  above  which  it  takes 
its  course.  It  is  crossed  by  the  vas 
deferens ;  and,  in  the  female,  by  the  round 
ligament  of  the  uterus. 

The  course  and  distribution  of  the  ar- 
tery have  been  already  given  (page  40), 
as  well  as  that  of  the  circumflexa  ilii. 

The  internal  iliac  artery  will  be  de- 
scribed with  the  anatomy  of  the  pelvis. 

INFERIOR  YENA  CAVA. — The  in- 
ferior vena  cava  is  formed  by  the 
union  of  the  two  common  iliac 
veins,  upon  the  intervertebral  sub- 
stance of  the  fourth  and  fifth  lumbar 
vertebras.  It  ascends  along  the 
front  of  the  vertebral  column,  on 

A  VIEW  OF  THE  VEINS  OF  THE  TRUNK  AND  NECK. — 1.  The  descending  vena 
cava.  2.  The  left  vena  innominata.  3.  The  right  vena  innominata.  4.  The 
right  subclavian  vein.  5.  The  internal  jugular  vein.  6.  The  external  jugular. 
7.  The  anterior  jugular.  8.  The  inferior  vena  cava.  9.  The  external  iliac  vein. 
10.  The  internal  iliac  vein.  11.  The  primitive  iliac  veins.  12,  12.  Lumbar 
veins.  13.  The  right  spermatic  vein.  14.  The  left  spermatic  vein.  15.  The 
right  emulgent  vein.  16.  The  trunk  of  the  hepatic  veins.  17.  The  vena  azygos. 
18.  The  hemi-azygos.  19.  A  branch  communicating  with  the  left  renal  vein. 
20.  The  termination  of  the  hemi-azygos  in  the  vena  azygos.  21.  The  superior 
intercostal  vein. 


INFERIOR  VENA   CAVA.  101 

the  right  of  the  abdominal  aorta ;  and  passing  through  the  fissure 
in  the  posterior  border  of  the  liver,  and  the  quadrilateral  opening 
in  the  tendinous  centre  of  the  diaphragm,  terminates  in  the  infe- 
rior and  posterior  part  of  the  right  auricle.  There  are  no  valves 
in  this  vein. 

It  is  in  relation  from  below  upwards,  in  front  with  the  mesen- 
tery, transverse  duodenum,  portal  vein,  pancreas,  and  liver,  which 
latter  nearly  and  sometimes  completely  surrounds  it ;  behind  it 
rests  on  the  vertebral  column  and  right  crus  of  the  diaphragm, 
from  which  it  is  separated  by  the  right  renal  and  right  lumbar 
arteries ;  to  the  right  it  has  the  peritoneum  and  sympathetic  nerve  ; 
and  to  the  left,  the  aorta. 

The  branches  which  the  inferior  cava  receives  in  its  course  are, 
the— 

Lumbar,  Supra-renal, 

Right  spermatic,  Phrenic, 

Renal,  Hepatic. 

The  lumbar  veins,  three  or  four  in  number  on  each  side,  col- 
lect the  venous  blood  from  the  muscles  and  integument  of  the 
loins  and  spinal  veins ;  the  left  are  longer  than  the  right,  on 
account  of  the  position  of  the  vena  cava. 

The  right  spermatic  vein  is  formed  by  the  two  veins  which 
return  the  blood  from  the  venous  plexus  of  the  spermatic  cord. 
These  veins  follow  the  course  of  the  spermatic  artery,  and  unite 
to  form  the  single  trunk  which  opens  into  the  inferk>r  vena  cava. 
The  left  spermatic  vein  terminates  in  the  left  renal  vein. 

The  ovarian  veins  represent  the  spermatic  veins  of  the  male, 
and  collect  the  venous  blood  from  the  ovaries,  round  ligaments, 
Fallopian  tubes,  and  communicate  with  the  uterine  sinuses. 
They  terminate  as  in  the  male. 

The  renal  or  emulgent  veins  return  the  blood  from  the  kidneys ; 
their  branches  are  situated  in  front  of  the  divisions  of  the  renal 
arteries,  and  the  left  opens  into  the  vena  cava  somewhat  higher 
than  the  right.  The  left  is  longer  than  the  right  in  consequence 
of  the  position  of  the  vena  cava,  and  crosses  the  aorta  immedi- 
ately below  the  origin  of  the  superior  ^mesenteric  artery.  It 
receives  the  left  spermatic  vein,  which  terminates  in  it  at  right 
angles  ;  hence  the  more  frequent  occurrence  of  varicocele  on  the 
left  than  on  the  right  side. 

The  supra-renal  veins  terminate  partly  in  the  renal  veins,  and 
partly  in  the  inferior  vena  cava. 

The  phrenic  veins  return  the  blood  from  the  ramifications  of 
the  phrenic  arteries  ;  they  open  into  the  inferior  cava. 

The  EXTERNAL  ILIAC  VEIN  lies  to  the  inner  side  of  the  corre- 
sponding artery  at  the  os  pubis ;  but  gradually  gets  behind  it  as 

9* 


102  THE   DISSECTOR. 

it  passes  upwards  along  the  brim  of  the  pelvis,  and  terminates 
opposite  the  sacro-iliac  symphysis,  by  uniting  with  the  internal 
iliac,  to  form  the  common  iliac  vein.  Immediately  above  Pou- 
part's  ligament  it  receives  the  epigastric  and  circumflexa  ilii 
vein  ;  it  has  no  valves. 

The  INTERNAL  ILIAC  VEIN  is  formed  by  vessels  which  corre- 
spond with  the  branches  of  the  internal  iliac  artery  ;  it  lies  to  the 
inner  side  of  the  internal  iliac  artery,  and  terminates  by  uniting 
with  the  external  iliac  vein,  to  form  the  common  iliac. 

The  COMMON  ILIAC  VEINS  are  formed  by  the  union  of  the  external 
and  internal  iliac  vein  on  each  side  of  the  pelvis.  The  right  com- 
mon iliac,  shorter  than  the  left,  ascends  obliquely  behind  the  cor- 
responding artery  ;  and  upon  the  intervertebral  substance  of  the 
fourth  and  fifth  lumbar  vertebra,  unites  with  the  vein  of  the 
opposite  side,  to  form  the  inferior  cava.  The  left  common  iliac, 
longer  and  more  oblique  than  the  right,  ascends  behind  and  a 
little  internally  to  the  corresponding  artery,  and  passes  beneath 
the  right  common  iliac  artery,  near  its  origin,  to  unite  with  the 
right  vein  in  the  formation  of  the  inferior  vena  cava.  The  right 
common  iliac  vein  has  no  branch  opening  into  it ;  the  left 
receives  the  vena  sacra  media.  These  veins  have  no  valves. 

The  SYMPATHETIC  NERVE,  within  the  abdomen,  consists  of  a 
prevertebral  portion  which  is  distributed  to  the  viscera,  and  a 
vertebral  portion  which  is  the  proper  continuation  of  the  nerve 
on  the  vertebral  column. 

The  prevertebral  portion  consists  of  the  epigastric  or  solar, 
and  the  hypogastric  plexus,  with  the  numerous  secondary  plex- 
uses to  which  the  former  gives  origin. 

The  epigastric,  or  solar  plexus,  is  an  intricate  interlacement 
of  nervous  cords  and  branches,  situated  around  the  coeliac  axis 
and  origin  of  the  superior  mesenteric  artery,  and  resting  upon 
the  aorta  and  crura  of  the  diaphragm.  Laterally  it  extends  on 
each  side  to  the  supra-renal  capsules,  and  is  covered  in  by  the 
stomach,  and  on  the  right  side  by  the  inferior  vena  cava.  Besides 
the  nerves,  the  epigastric  plexus  has  entering  into  its  structure 
several  nervous  ganglia,  and  especially  two  of  large  size,  the 
semilunar  ganglia. 

The  semilunar  ganglion  is  a  large  irregular  gangliform  body, 
pierced  by  numerous  openings,  and  appearing  like  the  aggrega- 
tion of  a  number  of  smaller  ganglia,  having  spaces  between  them. 
It  is  situated  by  the  side  of  the  coeliac  axis  and  root  of  the  supe- 
rior mesenteric  artery,  and  extends  outwards  to  the  supra-renal 
capsules.  The  ganglia  communicate  both  above  and  below  the 
coeliac  axis,  and  constitute  a  gangliform  circle  from  which  branches 
pass  off  in  all  directions,  like  rays  from  a  centre.  Hence  the  ap- 
pellation solar  plexus. 


HYPOGASTRIC   PLEXUS.  103 

The  epigastric  plexus  receives  the  great  splanchnic  nerves  ;  part 
of  the  lesser  splanchnic  nerves  ;  the  termination  of  the  right  pneu- 
mogastric  nerve  ;  some  branches  from  the  right  phrenic  nerve ; 
and  sometimes  one  or  two  filaments  from  the  left.  It  sends  forth 
numerous  filaments  which  accompany,  under  the  name  of  plexuses, 
all  the  branches  given  off  by  the  abdominal  aorta.  Thus  we  have, 
derived  from  this  plexus,  the — 

Phrenic,    or    diaphragmatic     Supra-renal  plexuses,      _ 
plexuses,  Renal  plexuses, 

Gastric  plexus,  Superior  mesenteric  plexus, 

Hepatic  plexus,  Aortic  plexus, 

Splenic  plexus,  Spermatic  plexuses, 

Inferior  mesenteric  plexuses. 

In  connection  with  the  phrenic  plexus  of  the  right  side  there  is 
described  a  small  ganglion  diaphragmaticum,  which  is  situated 
near  the  supra-renal  capsule.  In  this  ganglion  branches  of  the 
right  phrenic  nerve  communicate  with  those  of  the  sympathetic. 

The  supra-renal  plexuses  are  remarkable  for  their  large  size, 
and  for  a  ganglion,  which  has  received  the  name  of  ganglion 
supra-renale. 

The  renal  plexuses  are  also  large,  and  receive  the  third  splanchnic 
nerve. 

The  superior  mesenteric  plexus  has  several  small  ganglia  at  the 
root  of  the  artery  and  its  nerves,  which  are  whiter  than  those  of 
the  other  plexuses,  form  a  kind  of  nervous  sheath  to  the  artery 
and  its  branches. 

The  aortic  plexus  is  a  continuation  of  the  solar  plexus  down- 
wards on  the  aorta,  for  the  supply  of  the  inferior  branches  of  that 
trunk  ;  it  receives  also  branches  from  the  renal  plexuses  and  from 
the  lumbar  ganglia.  It  is  the  source  or  origin  of  the  inferior 
mesenteric  plexus,  and  part  of  the  spermatic  plexus,  and  it  ter- 
minates below  in  the  hypogastric  plexus.  It  likewise  distributes 
branches  on  the  inferior  vena  cava. 

The  spermatic  plexus  is  derived  from  the  renal  plexus,  but  re- 
ceives filaments  from  the  aortic  plexus. 

The  inferior  mesenteric  plexus  is  derived  chiefly  from  the  aortic 
plexus. 

The  HYPOGASTRIC  PLEXUS  is  formed  by  the  termination  of  the 
aortic  plexus,  and  by  the  union  of  branches  from  the  lower  lumbar 
ganglia.  It  is  situated  over  the  promontory  of  the  sacrum,  between 
the  two  common  iliac  arteries,  and  bifurcates  inferiorly  into  two 
lateral  portions,  inferior  hypogastric  plexuses,  which  communicate 
with  branches  from  the  third  and  fourth  sacral  nerves.  It  dis- 
tributes branches  to  all  the  viscera  of  the  pelvis,  and  sends  fila- 
ments which  accompany  the  branches  of  the  internal  iliac  artery. 


104  THE   DISSECTOR. 

The  VERTEBRAL  portion,  or  trunk  of  the  sympathetic,  is  situated 
on  the  vertebral  column,  close  to  the  anterior  border  of  the  psoas 
magnus  muscle.  It  is  continuous  above,  under  the  edge  of  the 
diaphragm,  with  the  thoracic  portion  of  the  nerve,  and  below  it 
descends  upon  the  sacrum,  in  front  of  the  anterior  sacral  foramina, 
to  the  coccyx.  It  presents  four  small  lumbar  ganglia  which  are 
fusiform  in  shape  and  of  a  pearly  gray  color. 

The  branches  given  off  by  the  ganglia  are  branches  of  commu- 
nication and  branches  of  distribution. 

The  branches  of  communication  are  ascending  and  descending 
to  the  ganglion  above  and  below. 

The  branches  of  distribution  are  external  and  internal.  The 
external  branches,  two  or  three  in  number,  and  longer  than  in  the 
other  regions,  communicate  with  the  lumbar  nerves. 

The  internal  branches  consist  of  two  sets ;  of  which  the  upper 
pass  inwards  in  front  of  the  abdominal  aorta,  and  join  the  aortic 
plexus ;  the  lower  branches  cross  the  common  iliac  arteries,  and 
unite  over  the  promontory  of  the  sacrum,  to  form  the  hypogastric 
plexus. 

LYMPHATIC  VESSELS  AND  GLANDS. — The  deep  lymphatic  glands 
of  the  abdomen  are  the  lumbar  glands;  they  are  very  numerous, 
and  are  seated  around  the  common  iliac  vessels,  the  aorta  and 
vena  cava. 

The  deep  lymphatic  glands  of  the  pelvis  are  the  external  iliac, 
internal  iliac,  and  sacral. 

The  external  iliac  are  placed  around  the  external  iliac  vessels, 
being  in  continuation  by  one  extremity  with  the  femoral  lymph- 
atics, and  by  the  other  with  the  lumbar  glands. 

The  internal  iliac  glands  are  situated  in  the  course  of  the  in- 
ternal iliac  vessels,  and  the  sacral  glands  are  supported  by  the 
concave  surface  of  the  sacrum. 

The  deep  lymphatic  vessels  are  continued  upwards  from  the 
thigh,  beneath  Poupart's  ligament,  and  along  the  external  iliac 
vessels  to  the  lumbar  glands,  receiving  in  their  course  the  epi- 
gastric, circumflexa  ilii,  and  ilio-lumbar  lymphatic  vessels.  Those 
from  the  parietes  of  the  pelvis,  and  from  the  gluteal,  ischiatic, 
and  obturator  vessels  follow  the  course  of  the  internal  iliac  arteries, 
and  unite  with  the  lumbar  lymphatics.  And  the  lumbar  lymph- 
atic vessels,  after  receiving  all  the  lymphatics  from  the  lower 
extremities,  pelvis,  and  loins,  terminate  by  several  large  trunks 
in  the  receptaculum  chyli. 

To  see  the  receptaculum  chyli  and  commencement  of  the  thoracic  duct, 
the  inferior  vena  cava  which  was  divided  on  the  removal  of  the  liver,  and 
drawn  aside  for  the  examination  of  the  right  semilunar  ganglion,  should 
now  he  further  drawn  aside  or  turned  down  to  reach  the  vertebral  column. 
Any  cellular  tissue  and  fat  which  may  impede  the  view,  should  be  removed. 


DIAPHRAGM.  105 

The  receptaculum  cihyli  is  a  triangular  oblong  sac,  the  reservoir 
of  the  lymphatics  of  the  lower  half  of  the  body ;  it  is  situated  on 
the  front  of  the  body  of  the  second  lumbar  vertebra,  behind  and 
between  the  aorta  and  inferior  vena  cava,  and  close  to  the  tendon 
of  the  right  crus  of  the  diaphragm.  It  receives,  by  its  lower  part, 
four  or  live  large  lymphatic  trunks,  and  above,  where  it  becomes 
narrowed,  in  order  to  constitute  the  thoracic  duct,  it  is  joined  by 
the  trunks  of  the  lacteals.  The  upper  part  of  the  receptaculum 
chyli  contracts  its  dimensions  to  the  size  of  a  small  quill,  and  be- 
comes the  thoracic  duct,  which  ascends  through  the  aortic  opening 
in  the  diaphragm,  to  terminate  in  the  root  of  the  neck  at  the 
junction  of  the  left  internal  jugular  with  the  left  subclavian  vein. 
In  the  aortic  opening,  and  between  the  two  crura  of  the  diaphragm, 
it  is  situated  between  the  aorta,  which  is  to  the  left,  and  the  vena 
azygos  major,  which  is  to  the  right. 

DEEP  MUSCLES  OF  THE  ABDOMEN. 

The  deep  muscles  of  the  abdomen  are,  the—- 
Diaphragm, Psoas  parvus, 
Psoas  magnus,  Iliacus  internus, 

Quadratus  lumborum. 

The  peritoneum  should  now  be  dissected  carefully  from  the  surface  of 
the  diaphragm,  and  any  cellular  tissue  or  fat  removed  which  may  in  any 
way  obscure  it.  Its  border  of  attachment  to  the  ribs,  and  particularly  its 
posterior  border  and  the  lesser  muscle,  should  also  be  carefully  made  out. 

The  DIAPHRAGM  is  the  muscular  septum  between  the  thorax 
and  abdomen,  and  is  composed  of  two  portions,  a  greater  and  a 
lesser  muscle.  The  greater  muscle  arises  from  the  eusiform  carti- 
lage ;  from  the  inner  surface  of  the  six  inferior  ribs,  indigitating 
with  the  transversalis ;  and  from  the  ligamentnm  arcuatum  ex- 
ternum  and  internum.  From  these  points,  which  form  the  internal 
circumference  of  the  trunk,  the  fibres  converge  and  are  inserted 
into  the  central  tendon. 

The  ligamentum  arcuatum  externum  is  the  upper  border  of  the 
anterior  lamella  of  the  aponeurosis  of  the  transversalis  ;  it  arches 
across  the  origin  of  the  quadratus  lumborum  muscle,  and  is 
attached,  by  one  extremity,  to  the  base  of  the  transverse  process 
of  the  first  lumbar  vertebra,  and  by  the  other,  to  the  apex  and 
lower  margin  of  the  last  rib. 

The  ligamentum  arcuatum  intemum,  OT  proprium,  is  a  tendinous 
arch  thrown  across  the  psoas  magnus  muscle  as  it  emerges  from 
the  chest.  It  is  attached  by  one  extremity  to  the  base  of  the 
transverse  process  of  the  first  lumbar  vertebra,  and  by  the  other 
is  continuous  with  the  tendon  of  the  lesser  muscle  opposite  the 
body  of  the  second. 


106  THE   DISSECTOR. 

The  tendinous  centre  of  the  diaphragm  is  shaped  like  a  trefoil 
leaf,  of  which  the  central  leaflet  points  to  the  ensiform  cartilage, 


THE  UNDER  OR  ABDOMINAL  SIDE  or  THE  DIAPHRAGM. — 1,  2,  3.  The  greater 
muscle  ;  the  figure  1  rests  upon  the  central  leaflet  of  the  tendinous  centre  ;  the 
number  2  on  the  left  or  smallest  leaflet ;  and  number  3  on  the  right  leaflet.  4. 
The  thin  fasciculus  which  arises  from  the  ensiform  cartilage  ;  a  small  triangular 
space  is  left  on  either  side  of  this  fasciculus,  which  is  closed  only  by  the  serous 
membrane  of  the  abdomen  and  chest.  5.  The  ligamentum  arcuatum  externum 
of  the  left  side.  6.  The  ligamentum  arcuatum  internum.  7.  A  small  arched 
opening  occasionally  found,  through  which  the  lesser  splanchnic  nerve  passes. 
8.  The  right  or  larger  tendon  of  the  lesser  muscle  ;  a  muscular  fasciculus  from 
this  tendon  curves  to  the  left  side  of  the  greater  muscle  between  the  oesophageal 
and  aortic  openings.  9.  The  fourth  lumbar  vertebra.  10.  The  left  or  shorter 
tendon  of  the  lesser  muscle.  11.  The  aortic  opening  occupied  by  the  aorta, 
which  is  cut  short  off.  12.  A  portion  of  the  oesophagus  issuing  through  the 
oesophageal  opening.  13.  The  opening  for  the  inferior  vena  cava,  in  the  ten- 
dinous centre  of  the  diaphragm.  14.  The  psoas  magnus  muscle  passing  beneath 
the.  ligamentum  arcuatum  internum  ;  it  has  been  removed  on  the  opposite  side 
to  show  the  arch  more  distinctly.  15.  The  quadratus  lumborum  passing  beneath 
the  ligamentum  arcuatum  externum  ;  this  muscle  has  also  been  removed  on  the 
left  side. 

and  is  the  largest ;  the  lateral  leaflets,  right  and  left,  occupy  the 
corresponding  portions  of  the  muscle;  the  right  being  the  larger 
and  more  rounded,  and  the  left  smaller  and  lengthened  in  its  form. 
Between  the  sides  of  the  ensiform  cartilage  and  the  cartilages 
of  the  adjoining  ribs,  is  a  small  triangular  space  where  the  mus- 
cular fibres  of  the  diaphragm  are  deficient.  This  space  is  closed 
only  by  peritoneum  on  the  side  of  the  abdomen,  and  by  pleura 


THE   DIAPHRAGM.  lOt 

within  the  chest.  It  is  therefore  a  weak  point,  and  a  portion  of 
the  contents  of  the  abdomen  might,  by  violent  exertion,  be  forced 
through  it,  producing  phrenic,  or  diaphragmatic  hernia. 

The  lesser  muscle  of  the  diaphragm  takes  its  origin  from  the 
bodies  of  the  lumbar  vertebrae,  by  two  tendons.  The  right,  larger 
and  longer  than  the  left,  arises  from  the  anterior  surface  of  the 
bodies  of  the  second,  third,  and  fourth  vertebrae ;  and  the  left, 
from  the  side  of  the  second  and  third.  The  tendons  form  two 
large  fleshy  bellies  (crura,  pillars),  which  ascend,  to  be  inserted 
into  the  central  tendon.  The  inner  fasciculi  of  the  two  crura 
cross  each  other  in  front  of  the  aorta,  and  again  diverge,  to  sur- 
round the  resophagus,  so  as  to  present  the  appearance  of  a  figure 
of  eight.  The  anterior  fasciculus  of  the  decussation  is  formed  by 
the  right  crus. 

The  openings  in  the  diaphragm  are  three :  one,  quadrilateral, 
in  the  tendinous  centre,  at  the  union  of  the  right  and  middle 
leaflets,  for  the  passage  of  the  inferior  vena  cava ;  a  muscular 
opening  of  an  elliptic  shape  formed  by  the  two  crura,  for  the 
transmission  of  the  oesophagus  and  pneumogastric  nerves  ;  and  a 
third,  the  aortic,  which  is  formed  by  a  tendinous  arch  thrown 
from  the  tendon  of  one  crus  to  that  of  the  other,  beneath  which 
pass  the  aorta,  the  right  vena  azygos,  and  the  thoracic  duct.  The 
great  splanchnic  nerves  pass  through  openings  in  the  lesser  muscle 
on  each  side ;  and  the  lesser  splanchnic  nerves,  between  the 
fibres  which  arise  from  the  ligamentum  arcuatum  internum. 

The  diaphragm,  being  interposed  between  the  viscera  of  the  chest  and 
abdomen,  is  important  in  its  relations  to  the  organs  contained  in  the  two 
cavities.  Above  it  is  in  contact  with  the  pleurae,  pericardium,  heart,  and 
lungs.  By  its  inferior  surface,  with  the  peritoneum ;  on  the  left,  with  the 
stomach  and  spleen  ;  on  the  right,  with  the  convexity  of  the  liver  ;  and 
behind,  with  the  kidneys,  supra-renal  capsules,  duodenum,  and  solar 
plexus.  By  its  circumference,  with  the  ribs,  intercostal  muscles,  and  ver- 
tebral column. 

To  see  the  next  muscle,  the  psoas  magnus,  a  thin  fascia  must  be  laid 
open  and  turned  aside.  This  fascia  is  a  prolongation  upwards  of  the  iliac 
fascia,  much  attenuated  in  substance.  It  is  attached  to  the  bodies  of  the 
vertebrae,  leaving  an  arched  space  corresponding  with  the  constricted  por- 
tion of  each  vertebra,  for  the  passage  of  the  lumbar  vessels  and  external 
branches  of  the  sympathetic  nerve.  Externally  it  is  connected  with  .the 
aponeurosis  of  the  transversalis  muscle  ;  and  above,  with  the  ligamentum 
arcuatum  internum.  Lower  down  it  is  attached  to  the  brim  of  the  pelvis. 
The  removal  of  the  fascia  brings  into  view  the  psoas  magnus  and  parvus, 
and  a  nerve  which  pierces  the  muscle  at  about  its  middle  and  lies  upon  its 
anterior  surface,  the  genito-crural ;  care  must  be  taken  not  to  injure  this 
nerve  in  the  dissection  of  the  fascia. 

The  PSOAS  MAGNUS  (^oa,  lumbus),  situated  by  the  side  of  the 
vertebral  column  in  the  loin,  is  a  long  fusiform  muscle.  It  arises 
from  the  sides  of  the  bodies  of  the  last  dorsal  and  all  the  lumbar 
vertebrae,  from  their  intervertebral  substances,  transverse  pro- 


108  THE   DISSECTOR. 

cesses,  and  the  tendinous  arches  which  are  thrown  across  the 
constricted  portion  of  the  vertebras,  to  protect  the  lumbar  arte- 
ries and  external  branches  of  the  sympathetic  nerve  from  pres- 
sure in  their  passage  beneath  the  muscle.  From  this  extensive 
origin  the  muscle  passes  along  the  brim  of  the  pelvis  and  beneath 
Poupart's  ligament  to  its  insertion  into  the  trochanter  minor  of 
the  femur. 

This  muscle  issues  from  beneath  the  ligamentum  arcuatum  internum 
above,  and  is  in  relation,  by  its  anterior  surface,  with  the  psoas  parvus, 
kidney,  and  genito-crural  nerve  which  pierces  it  at  about  its  middle  and 
then  lies  on  its  anterior  surface.  By  its  inner  border  and  surface  it  is  in 
relation  with  the  lumbar  vessels,  the  sympathetic  nerve  with  its  external 
branches,  and,  lower  down,  with  the  iliac  vessels.  Its  substance  is  tra- 
versed by  the  nerves  constituting  the  lumbar  plexus ;  and  in  the  iliac 
fossa  it  has,  escaping  from  beneath  it  and  then  lying  along  its  outer  border, 
the  anterior  crural  nerve. 

The  PSOAS  PARVUS  is  a  small  and  infrequent  muscle,  which 
arises  from  the  last  dorsal  and  first  lumbar  vertebra,  and  from  the 
intervertebral  substance  between  them ;  it  passes  beneath  the 
ligamentum  arcuatum  internum,  and  terminates  in  a  long  slender 
tendon  which  expands  inferiorly,  and  is  inserted  into  the  ilio-pec- 
tineal  line  and  eminence.  The  tendon  is  continuous,  by  its  outer 
border,  with  the  iliac  fascia. 

To  see  the  abdominal  or  pelvic  portion  of  the  iliacus  interims  muscle, 
the  iliac  fascia  must  be  removed,  and  care  must  be  taken  to  avoid  injury 
to  a  nerve  which  crosses  the  iliacus  muscle,  the  external  cutaneous,  and 
the  anterior  crural  nerve  which  lies  in  the  groove  between  the  psoas  and 
iliacus. 

The  iliac  fascia  is  a  thin  aponeurosis  which  covers  in  the 
iliacus  muscle,  and  is  continued  upwards  upon  the  front  of  the 
psoas  to  the  ligamentum  arcuatum  internum.  It  is  attached  to 
the  inner  lip  of  the  crest  of  the  ilium,  and  passing  behind  the 
iliac  vessels,  is  connected  with  the  brim  of  the  pelvis,  Inferiorly, 
at  Poupart's  ligament,  it  is  connected  with  the  fascia  transver- 
salis,  and  at  the  inner  third  of  that  ligament  forms  the  posterior 
part  of  the  femoral  sheath. 

The  ILIACUS  MUSCLE  arises  from  the  whole  extent  of  the  inner 
concave  surface  of  the  ilium ;  and  by  a  few  fibres  from  the  base 
of  the  sacrum.  This  muscle  passes  beneath  Poupart's  ligament, 
to  be  inserted  with  the  psoas  into  the  trochanter  minor  of  the 
femur. 

The  QUADRATUS  LUMBORUM  muscle  is  concealed  from  view  by 
the  anterior  lamella  of  the  aponeurosis  of  the  transversalis  muscle, 
which  is  inserted  into  the  bases  of  the  transverse  processes  of 
the  lumbar  vertebrae.  When  this  lamella  is  divided,  the  muscle 
will  be  seen  to  consist  of  two  portions:  one,  the  external,  arising 
from  the  ilio-lumbar  ligament  and  crest  of  the  ilium  for  two  inches 


LUMBAR   NERVES.  109 

in  extent,  and  inserted  into  the  apices  of  the  transverse  processes 
of  the  four  upper  lumbar  vertebrae  (sometimes  also  the  last 
dorsal),  and  last  rib  ;  the  other,  the  inner  and  anterior  portion, 
arises  by  tendinous  slips  from  the  transverse  processes  of  the 
three  or  four  lower  lumbar  vertebrae,  and  passes  upwards,  to  be 
inserted  into  the  lower  border  of  the  last  rib.  If  the  muscle  be 
cut  across  or  removed,  the  middle  lamella  of  the  transversalis  will 
be  seen  attached  to  the  apices  of  the  transverse  processes ; 
the  quadratus  being  inclosed  between  the  two  lamellae  as  in  a 
sheath. 

ACTIONS. — The  diaphragm  is  an  inspiratory  muscle,  the  contraction  of 
its  fibres  increasing  the  cavity  of  the  chest.  It  acts  also  as  a  muscle  of 
expulsion  by  pressing  upon  the  abdominal  viscera,  as  in  the  expulsion  of 
the  excretions,  of  the  foetus,  &c.  The  spasmodic  action  of  the  muscle  pro- 
duces hiccup,  sobbing,  &c. 

The  psoas  and  iliacus  muscles  flex  the  trunk  upon  the  lower  extremi- 
ties or  the  legs  upon  the  pelvis,  at  the  same  time  everting  the  foot.  The 
quadratus  lumborum  is  -an  expiratory  muscle,  and  assists  in  fixing  the 
chest. 

The  psoas  magnus,  if  not  previously  removed  for  the  examination  of 
the  quadratus  lumborum,  must  now  be  carefully  dissected  from  its  origin, 
for  the  purpose  of  bringing  into  view  the  lumbar  plexus  of  nerves,  which 
is  situated  in  the  substance  of  the  muscle. 

LUMBAR   NERVES. 

There  are  five  pairs  of  lumbar  nerves,  of  which  the  first  makes 
its  appearance  between  the  first  and  second  lumbar  vertebrae, 
and  the  last  between  the  fifth  lumbar  and  the  base  of  the  sacrum. 
The  anterior  branches  increase  in  size  from  above  downwards. 
At  their  exit  from  the  intervertebral  foramina  they  receive  the 
external  branch  of  the  lumbar  ganglia  of  the  sympathetic,  and 
pass  obliquely  outwards  behind  the  psoas  magnus,  or  through 
its  substance,  sending  twigs  to  that  muscle  and  to  the  quadratus 
lumborum.  In  this  situation  each  nerve  divides  into  two 
branches  :  a  superior  branch,  which  ascends,  to  form  a  loop  of 
communication  with  the  nerve  above  ;  and  an  inferior  branch, 
which  descends,  to  join  in  like  manner  the  nerve  below.  The 
communications  and  anastomoses  which  are  thus  established,  con- 
stitute the  lumbar  plexus. 

The  posterior  branches  diminish  in  size  from  above  downwards ; 
they  pass  backwards  between  the  transverse  processes  of  the 
corresponding  vertebrae,  and  each  nerve  divides  into  an  internal 
and  an  external  branch.  The  internal  branch,  the  smaller  of  the 
two,  passes  inwards,  to  be  distributed  to  the  multifidus  spinee 
and  interspinales ;  and  becoming  cutaneous,  supplies  the  integu- 
ment of  the  lumbar  region  on  the  middle  line.  The  external 
branches  communicate  with  each  other  by  several  loops  j  and 
10 


110 


THE  DISSECTOR. 


after  supplying:  the  deeper  muscles,  pierce  the  sacro-lumbalis,  to 
reach  the  integument  to  which  they  are  distributed.  The  exter- 
nal branches  of  the  three  lower  lumbar  nerves  (nervi  clunium 
superiores  postici),  descend  over  the  posterior  part  of  the  crest 
of  the  ilium,  and  are  distributed  to  the  integument  of  the  gluteal 
region. 

LUMBAR  PLEXUS. — The  lumbar  plexus  is  formed  by  the  com- 
munications and  anastomoses  which  take  place  between  the  an- 
terior branches  of  the  four  upper  lumbar  nerves,  and  between 
the  latter  and  the  last  dorsal.  It  is  narrow  above,  increases  in 
breadth  inferiorly,  and  is  situated  between  the  transverse  pro- 
cesses of  the  lumbar  ver- 
tebrae  and  quadratus  lura- 
borum  behind,  and  the 
psoas  magnus  muscle  in 
front. 

The  branches  of  the  lum- 
bar plexus  are,  the — 
Ilio-hypogastric, 
Ilio-ingumal, 
Genito-crural, 
External  cutaneous, 
Obturator, 
Anterior  crural. 

The       ILIO-HYPOGASTRIC 

NERVE  proceeds  from  the 
first  lumbar  nerve,  and 
passes  obliquely  outwards 
between  the  fibres  of  the 
psoas  magnus,  and  across 
the  quadratus  lumborum  to 
about  the  middle  of  the 
crest  of  the  ilium.  It  then 
pierces  the  transversalis 
muscle,  and  between  it  and 
the  internal  oblique  divides 
into  its  two  terminal 
branches,  iliac  and  hypo- 
gastric;  the  former  being 

THE  LUMBAR  PLEXUS  AND  ITS  BRANCHES  (slightly  altered  from  Schmidt). — 
a.  Last  rib.  b.  Quadratus  lumborum  muscle,  c.  Oblique  and  transverse  mus- 
cles, cut  near  the  crest  of  the  ilium,  d.  Os  pubis.  e.  Adductor  brevis  muscle. 
f.  Pectineus.  g.  Adductor  longus.  1.  Ilio-hypogastric  branch.  2.  Ilio-in- 
guinal.  3.  External  cutaneous  branch.  4.  Anterior  crural  nerve.  5.  Acces- 
sory obturator.  6.  Obturator  nerve.  7.  Genito-crural  nerve  divided  into  two 
at  its  origin  from  the  plexus.  8.  Gangliated  cord  of  the  sympathetic  nerve. 


ANTERIOR  CRURAL  NERVE.  Ill 

distributed  to  the  integument  of  the  hip  ;  and  the  latter,  to  that 
of  the  hypogastric  region  and  external  organs  of  generation 
(page  32). 

The  ILIO-INGUINAL  NERVE,  smaller  than  the  preceding,  also 
arises  from  the  first  lumbar  nerve.  It  passes  obliquely  down- 
wards and  outwards  below  the  ilio-hypogastric  nerve,  and  crosses 
the  quadratus  lumborum  and  iliacus  muscle  in  its  course  to  the 
anterior  part  of  the  crest  of  the  ilium  :  it  then  pierces  the  trans- 
versalis  muscle  ;  next,  the  internal  oblique ;  and  escaping  at  the 
external  abdominal  ring  with  the  spermatic  cord,  is  distributed 
to  the  scrotum  and  inner  part  of  the  thigh ;  in  the  female,  to  the 
pudendum  (page  32). 

The  GENITO-CRURAL  NERVE  proceeds  from  the  second  lumbar 
nerve,  and  by  a  few  fibres  from  the  loop  between  it  and  the  first. 
It  traverses  the  psoas  magnus  from  behind  forwards,  and  runs 
down  the  anterior  surface  of  that  muscle,  lying  beneath  its  fascia, 
to  near  Pou partis  ligament,  where  it  divides  into  a  genital  and  a 
crural  branch. 

The  genital  branch  (n.  spermaticus,  seu  pudendus  externus) 
crosses  the  external  iliac  artery  to  the  internal  abdominal  ring, 
and  descends  along  the  posterior  aspect  of  the  spermatic  cord  to 
the  scrotum.  It  is  distributed  to  the  cord  and  cremaster  muscle  ; 
and,  in  the  female,  to  the  round  ligament  and  labium  pudendi 
(page  45). 

The  crural  branch  (lumbo-inguinalis)  descends  along  the  outer 
side  of  the  external  iliac  artery,  and,  crossing  the  origin  of  the 
circumflexa  ilii  artery,  enters  the  femoral  sheath  in  front  of  the 
femoral  artery.  It  pierces  the  sheath  below  Poupart's  ligament, 
and  is  distributed  to  the  integument  of  the  upper  and  inner  part 
of  the  thigh. 

The  EXTERNAL  CUTANEOUS  NERVE  (inguino-cutaneous)  pro- 
ceeds from  the  second  lumbar,  and  from  the  loop  between  it  and 
the  third.  It  pierces  the  posterior  fibres  of  the  psoas  muscle ; 
and  crossing  the  iliacus  lying  upon  the  iliac  fascia,  to  the  anterior 
superior  spinous  process  of  the  ilium,  passes  into  the  thigh  be- 
neath Poupart's  ligament.  It  is  distributed  to  the  integument 
of  the  outer  aspect  of  the  thigh  as  far  as  the  knee. 

The  ANTERIOR  CRURAL  NERVE  is  the  largest  of  the  divisions  of 
the  lumbar  plexus  :  it  is  formed  by  the  union  of  cords  from  the 
second,  third,  and  fourth  lumbar  nerves.  Emerging  from  be- 
neath the  psoas  muscle,  it  passes  downwards  in  the  groove  be- 
tween the  psoas  and  iliacus,  and  beneath  Poupart's  ligament, 
into  the  thigh.  At  Poupart's  ligament  it  is  separated  from  the 
femoral  artery  by  the  breadth  of  the  psoas  muscle,  which  at  this 
point  is  scarcely  more  than  half  an  inch  in  diameter,  and  by  the 
iliac  fascia  beneath  which  it  lies. 


112       .  THE   DISSECTOR. 

Its  branches  within  the  pelvis  are  three  or  four  twigs  to  the 
iliaous  muscle,  and  a  long  filament  to  the  femoral  artery. 

The  OBTURATOR  NERVE  is  formed  by  a  branch  from  the  third, 
and  another  from  the  fourth  lumbar  nerve ;  it  takes  its  course 
among  the  fibres  of  the  psoas  muscle,  through  the  angle  of  bifur- 
cation of  the  common  iliac  vessels,  and  along  the  inner  border  of 
the  brim  of  the  pelvis,  to  the  obturator  foramen,  where  it  joins 
the  obturator  artery,  and  passes  into  the  thigh.  It  is  distributed 
to  the  muscles  of  the  inner  aspect  of  the  thigh,  and  to  the  hip 
and  knee-joint. 

A  small  nerve  is  sometimes  met  with  in  association  with  the 
obturator,  termed  the  accessory  obturator  nerve.  This  nerve  may 
be  a  high  division  of  the  obturator,  or  it  may  arise  separately 
from  the  third  and  fourth  lumbar  nerves.  It  passes  down  the 
inner  border  of  the  psoas  muscle,  and  crosses  the  os  pubis,  to 
enter  the  thigh. 

LUMBO-SACRAL  NERVE. — The  anterior  division  of  the  fifth 
lumbar  nerve,  conjoined  with  a  branch  from  the  fourth,  consti- 
tutes the  lumbo-sacral  nerve,  which  descends  over  the  base  of  the 
sacrum  into  the  pelvis,  and  assists  in  forming  the  sacral  plexus. 


CHAPTER   III. 

HEAD   AND   NECK. 

THE  head  may  be  considered  as  an  expansion  of  the  superior 
part  of  the  vertebral  column,  for  the  reception  of  the  brain  and 
the  principal  organs  of  sense. 

The  neck  is  the  medium  of  communication  and  connection  be- 
tween the  head  and  the  rest  of  the  body  :  communication,  by 
means  of  the  trachea  and  oasophagus,  with  the  internal  organs  ; 
connection,  by  means  of  the  muscles  and  vertebral  column,  with 
the  superficies  and  osseous  fabric  of  the  trunk. 

The  head  may  be  divided  into  the  cranium  and  face ;  the 
former  being  the  osseous  recipient  of  the  brain,  and  the  latter 
the  apparatus  for  the  development  and  protection  of  the  princi- 
pal organs  of  sense. 

The  exterior  of  the  cranium  presents  for  examination  its  con- 
vex surface,  and  on  its  sides  the  external  organs  of  hearing.  The 
face  is  more  varied,  comprehending,  the  orbits  for  the  organs  of 
vision  ;  the  nose  or  external  organ  of  smell ;  the  mouth,  con- 


MUSCLES   OP   THE   HEAD   AND   FACE. 


113 


taining  the  organ  of  taste  ;  and  the  jaws  or  apparatus  of  masti- 
cation. 

We  shall  commence  the  dissection  of  the  head  and  neck,  by 
devoting  one  side  to  the  examination  of  the  muscles,  reserving 
the  other  for  the  study  of  the  vessels  and  nerves. 

Fig.  33. 

THE  MUSCLES  OF  THE  HEAD  AND 
FACE. — 1.  The  frontal  portion  of  the 
occipito-frontalis.  2.  Its  occipital 
portion.  3.  Its  aponeurosis.  4.  The 
orbicularis  palpebrarum,  which  con- 
ceals the  corrugator  supercilii  and 
tensor  tarsi.  5.  The  pyrainidalis 
nasi.  6.  The  compressor  nasi.  7. 
The  orbicularis  oris.  8.  The  levator 
labii  superioris  alaeque  nasi.  The 
figure  is  placed  on  the  nasal  portion. 
9.  The  levator  labii  superioris  pro- 
prius  :  the  lower  part  of  the  levator 
anguli  oris  is  seen  between  the  mus- 
cles 10  and  11.  10.  The  zygomati- 
cus  minor.  11.  The  zygomaticua 
major.  12.  The  depressor  labii  in- 
ferioris.  13.  The  depressor  anguli 
oris.  14.  The  levator  labii  inferi- 
oris.  15.  The  superficial  portion  of 
the  masseter.  16.  Its  deep  portion. 
17.  The  attrahene  aurem.  18.  The 
buccinator.  19.  The  attollens aurem. 
20.  The  temporal  fascia  which  covers 
in  the  temporal  muscle.  21.  The 
retrahens  aurein.  22.  The  anterior  belly  of  the  digastricus  muscle  ;  the  tendon 
is  seen  passing  through  the  aponeurotic  pully.  23.  The  stylo-hyoid  muscle 
pierced  by  the  posterior  belly  of  the  digastricus.  24.  The  mylo-hyoideus 
muscle.  25.  The  upper  part  of  the  stern o-mastoid.  26.  The  upper  part  of  the 
trapezius.  The  muscle  between  25  and  26  is  the  splenius. 

into  certain  natural  groups,  which 
of  the  head  and  face  above  esta- 


The  MUSCLES  are  associated 
correspond  with  the  divisions 
blished  :  thus  we  find 

Cranial  group, 

Auricular  group, 

Orbital  group, 

Nasal  group, 

The  muscles  belonging  to  each  of  these  groups  may  be  thus 
arranged  : — 

1 .    Cranial  group. 
Occipito-frontalis. 


Superior  labial  group, 
Inferior  labial  group, 
Maxillary  group. 


2.  Auricular  group. 
Attollens  aurem, 
Attruhens  aurem, 
Retrahens  aurem. 


3.    Orbital  group. 
Orbicularis  palpebrarum, 
Corrugator  supercilii, 
Tensor  tarsi. 

4.  Nasal  group. 
Pyramidalis  nasi, 


10* 


114  THE   DISSECTOR. 

Compressor  nasi,  6.  Inferior  labial  group. 

Dilatator  naris,  (Orbicularis  oris),' 

Depressor  ala  nasi.  Depressor  labii  inferioris, 

5.   Superior  labial  group.  Depressor  anguli  oris, 

(Orbicularis  oris),1  Levator  labii  inferioris. 
Levator  labi  superioris  ateque  ^  jfaxOay  group. 

Levator    labi    superioris  pro-     Masseter, 

prius,  Buccinator, 

Levator  anguli  oris,  Temporalis, 

Zygomaticus  major,  Pterygoideus  externus, 

Zygomaticus  minor.  Pterygoideus  internus. 

The  surface  of  the  cranium  is  to  be  dissected  by  making  a  longitudinal 
incision  along  the  vertex  of  the  head  from  the  tubercle  on  the  occipital 
bone  to  the  root  of  the  nose,  and  a  second  incision  along  the  forehead 
and  around  the  side  of  the  head  to  join  the  two  extremities  of  the  pre- 
ceding. Dissect  the  integument  and  superficial  fascia  carefully  upwards 
and  outwards,  beginning  at  the  anterior  angle  of  the  flap,  where  the 
muscular  fibres  are  thickest.  Having  dissected  these  to  their  termina- 
tions in  the  aponeurosis,  it  will  now  be  best  to  proceed  to  the  posterior 
angle  made  by  the  above  incisions,  and  to  dissect  upwards,  taking  the 
posterior  fleshy  portion  of  the  muscle  as  a  guide ;  the  flap  can  then  care- 
fully be  raised  from  the  tendon,  and  the  muscle  fully  exposed.  This 
dissection  requires  care,  for  the  muscle  is  very  thin,  and  without  atten- 
tion would  be  raised  with  the  integument.  There  is  no  deep  fascia  on 
the  face  and  head,  nor  is  it  required,  for  here  the  muscles  are  closely 
applied  against  the  bones  upon  which  they  depend  for  support,  whilst  in 
the  extremities  the  support  is  derived  from  the  dense  layer  of  fascia  by 
which  they  are  invested,  and  which  forms  for  each  a  distinct  sheath. 

1.  Cranial  Group. — The  OCCIPITO-FRONTALIS  is  a  broad  mus- 
culo-aponeurotic  layer,  which  covers  the  whole  of  the  side  of  the 
vertex  of  the  skull,  from  the  occiput  to  the  eyebrow.  It  arises 
by  tendinous  fibres  from  the  outer  two-thirds  of  the  superior 
curved  line  of  the  occipital,  and  from  the  mastoid  portion  of  the 
temporal  bone.  Its  insertion  takes  place  by  means  of  the  blend- 
ing of  the  fibres  of  its  anterior  portion  with  those  of  the  orbicu- 
laris  palpebrarum,  corrugator  supercilii,  levator  labii  superioris 
alseque  nasi,  and  pyramidalis  nasi.  The  muscle  is  fleshy  in  front 
over  the  frontal  bone  and  behind  over  the  occipital,  the  two  por- 
tions being  connected  by  a  broad  aponeurosis.  The  two  muscles 
together  with  their  aponeurosis  cover  the  whole  of  the  vertex  of 
the  skull,  hence  their  designation  galea  capitis;  they  are  loosely 
adherent  to  the  pericranium,  but  very  closely  to  the  integument, 
particularly  over  the  forehead. 

1  The  Orbicularis,  from  encircling  the  mouth,  belongs  necessarily  to 
both  the  superior  and  inferior  labial  regions  ;  therefore,  to  prevent  mis- 
conception, we  have  inclosed  it  in  both  within  brackets. 


ATTOLLENS   AUREM — TEMPORAL   MUSCLE.  115 

The  action  of  the  occipito-frontalis  is  to  raise  the  eyebrows,  thereby 
throwing  the  integument  of  the  forehead  into  transverse  wrinkles. 
Some  persons  have  the  power  of  moving  the  entire  scalp  upon  the  peri- 
cranium by  means  of  these  muscles. 

2.  Auricular  Group. — Attollens  aurem, 
Attrahens  aurem, 
Retrahens  aurem. 

The  dissection  of  these  three  small  and  superficial  muscles  requires 
the  careful  removal  of  the  integument  from  around  the  pinna  ;  their 
exact  position  is  shown  by  drawing  the  pinna  from  the  side  of  the  head, 
and  they  may  be  conveniently  dissected  by  taking  the  prominent  lines 
which  they  thus  form  as  a  guide  for  the  incision. 

The  ATTOLLENS  AUREM  (superior  auriculae),  the  largest  of  the 
three,  is  a  thin  triangular  plane  of  muscular  fibres  arising  from 
the  edge  of  the  aponeurosis  of  the  occipito-frontalis,  and  inserted 
into  the  convexity  of  the  fossa  triangularis  and  scaphoidea. 

The  ATTRAHENS  AUREM  (anterior  auriculae),  also  triangular, 
arises  from  the  edge  of  the  aponeurosis  of  the  occipito-frontalis 
in  front  of  the  preceding,  and  is  inserted  into  the  spine  of  the 
helix. 

The  RETRAHENS  AUREM  (posterior  auriculae)  arises  by  two 
muscular  slips  from  the  root  of  the  mastoid  process.  They  are 
inserted  into  the  posterior  surface  of  the  concha. 

The  actions  of  the  auricular  muscles  are  expressed  in  their  names  ;  they 
have  but  little  power  in  man,  but  are  important  muscles  in  brutes. 

Beneath  the  attrahens  and  attollens  muscles  is  a  white  glistening  fascia 
which  may  now  be  examined. 

The  TEMPORAL  FASCIA  is  a  strong  aponeurotic  membrane,  which 
covers  in  the  temporal  muscle  at  each  side  of  the  head,  and  gives 
origin  by  its  internal  surface  to  some  of  its  fibres.  It  is  attached 
to  the  whole  extent  of  the  temporal  ridge  above,  and  to  the  zygo- 
matic  arch  below ;  in  the  latter  situation  it  is  thick,  and  consists 
of  two  layers,  the  external  being  connected  to  the  upper  border 
of  the  arch,  and  the  internal  to  its  inner  surface.  Some  fat  is 
found  between  these  two  layers,  and  also  the  orbital  branch  of  the 
temporal  artery. 

Separate  the  temporal  fascia  from  the  temporal  ridge,  and  turn  it  down- 
wards ;  the  temporal  muscle  will  then  be  exposed  in  the  greater  part  of 
its  extent.  Above,  the  muscle  is  rough,  from  the  necessity  of  dividing 
its  libres  in  the  removal  of  the  fascia  ;  below,  some  fat  and  cellular  tissue 
require  removal  to  make  it  clean. 

The  TEMPORAL  MUSCLE,  broad  and  radiating,  occupies  the  tem- 
poral fossa,  and  expands  over  the  side  of  the  head.  It  arises  by 
tendinous  fibres  from  the  temporal  ridge,  and  by  muscular  fibres 
from  the  surface  of  bone  constituting  the  temporal  fossa,  and  from 
the  temporal  fascia.  Its  fibres  converge  to  a  strong  and  narrow 


116  THE  DISSECTOR. 

tendon,  which  is  inserted  into  the  apex  and  internal  surface  of  the 
coronoid  process  of  the  lower  jaw. 

Having  now  examined  the  muscles  of  the  cranium,  with  the  view  to  a 
speedy  opening  of  the  skull  for  the  examination  of  the  brain,  the  student 
should  next  proceed  to  study  the  vessels  and  nerves  distributed  upon  the 
exterior  of  the  cranium,  and  which  would  be  destroyed  by  the  removal 
of  the  calvaria.  For  this  purpose  the  integument  covering  one  side  of 
the  head  has  been  left  undisturbed.  This  may  now  be  dissected  in  the 
manner  directed  for  the  dissection  of  the  muscles  (page  114),  the  integu- 
ment alone  being  removed,  and  the  superficial  fascia  in  which  the  vessels 
and  nerves  are  embedded  exposed  to  view. 

Vessels  and  Nerves  of  the  Cranium. — The  arteries  of  the  cra- 
nium are  the  supra-orbital  and  frontal  from  the  ophthalmic  ;  the 
temporal  artery ;  posterior  auricular  and  occipital. 

The  supra-orbital  artery  escapes  from  the  orbit  through  the 
supra-orbital  notch  in  company  with  the  supra-orbital  nerve,  and 
divides  into  a  superficial  and  deep  branch,  which  are  distributed 
to  the  integument  and  muscles  of  the  forehead  and  to  the  peri- 
cranium. 

The  frontal  artery,  one  of  the  terminal  branches  of  the  ophthal- 
mic, emerges  from  the  orbit  at  its  inner  angle  and  ascends  the 
middle  of  the  forehead,  to  which  it  is  distributed,  anastomosing 
with  its  fellow  of  the  opposite  side. 

The  temporal  artery,  one  of  the  terminal  branches  of  the  external 
carotid,  ascends  in  front  of  the  ear  and  divides  into  an  anterior 
and  a  posterior  branch.  The  anterior  temporal1  arches  forwards 
upon  the  temple,  and  is  distributed  to  the  integument  and  muscles 
of  the  scalp,  inosculating  with  the  supra-orbital  and  frontal  artery. 

The  posterior  temporal  curves  upwards  and  backwards  over  the 
ear,  and  inosculates  with  its  fellow  of  the  opposite  side,  and  with 
the  occipital  and  posterior  auricular  arteries. 

The  posterior  auricular  artery  ascends  in  front  of  the  mastoid 
process,  and  divides  into  two  branches,  one  of  which  supplies  the 
pinna  and  anastomoses  with  the  posterior  temporal,  while  the 
other  crosses  the  mastoid  process  to  the  posterior  portion  of  the 
occipito-frontalis,  and  inosculates  with  the  occipital  artery. 

The  occipital  artery,  emerging  from  between  the  splenius  and 
complexus,  and  piercing  the  trapezius  muscle,  ascends  upon  the 
occipito-frontalis  muscle,  and  divides  into  branches  which  supply 
that  muscle,  the  pericranium,  and  integument,  and  inosculate 
with  their  fellows  of  the  opposite  side,  the  posterior  temporal  and 
the  posterior  auricular  artery. 

The  veins  of  the  scalp  are  found  by  the  side  of  the  arteries.  The 
frontal  vein,  descending  the  mid-line  of  the  forehead  to  the  inner 
angle  of  the  orbit,  receives  the  supra-orbital  vein,  and  becomes 

1  This  is  the  vessel  which  is  selected  for  the  operation  of  arteriotomy. 


NERVES   OF   THE   CRANIUM.  117 

the  facial  vein.  The  temporal  and  posterior  auricular  veins  ter- 
minate in  the  external  jugular,  and  the  occipital  veins  in  the  in- 
ternal jugular. 

The  NERVES  distributed  to  the  cranium  are  the  supra-orbital 
and  supra-trochlear  branches  of  the  first  division  of  the  fifth  pair; 
temporal  branches  from  the  second  and  third  divisions  of  the 
fifth  and  from  the  facial  nerve  ;  posterior  auricular  from  the  facial ; 
auricularis  magnus  and  occipitalis  minor,  from  the  anterior  cervi- 
cal plexus;  and  occipitalis  major,  from  the  posterior  division  of 
the  second  cervical  nerve. 

The  supra-orbital  nerve,  issuing  from  the  orbit  through  the 
supra-orbital  notch  with  the  artery  of  the  same  name,  gives  fila- 
ments to  the  eyelids,  the  muscles  of  the  forehead  and  pericranium, 
and  divides  into  two  cutaneous  branches,  internal  and  external. 
The  internal  branch  pierces  the  occipito-f rental  is,  and  is  dis- 
tributed to  the  integument  as  far  as  the  summit  of  the  head.  The 
external  branch,  of  larger  size,  communicates  with  the  facial  nerve, 
and  piercing  the  occipito-frontalis,  is  distributed  to  the  integu- 
ment as  far  back  as  the  occiput. 

The  supra-trochlear  nerve  emerges  from  the  orbit  at  its  inner 
angle,  and  piercing  the  muscle,  is  distributed  to  the  integument 
in  the  middle  line  of  the  forehead. 

The  temporal  branch  of  the  second  division  of  the  fifth  or  superior 
maxillary  nerve  pierces  the  temporal  fascia  a  little  above  the 
zygoma,  and  is  distributed  to  the  integumejit  of  the  front  of  the 
temple.  It  communicates  with  the  facial  nerve. 

The  temporal  branches,  anterior  and  posterior,  of  the  auriculo- 
temporal  nerve,  a  branch  of  the  third  division  of  the  fifth  or 
inferior  maxillary  nerve,  ascend  upon  the  temple  in  front  of  the 
ear.  The  anterior  branch  is  distributed  to  the  integument  as  far 
as  the  summit  of  the  head.  The  posterior  branch  is  directed  back- 
wards over  the  external  ear,  and  supplies  the  integument,  after 
giving  twigs  to  the  attrahens  aurem  and  to  the  pinna. 

The  temporal  branches  of  the  facial  nerve,  two  or  three  in 
number,  pass  in  a  radiated  manner  over  the  temple,  and  are  dis- 
tributed to  the  attrahens  aurem,  occipito-frontalis,  and  orbicularis 
palpebrarum  muscle.  They  communicate  with  the  temporal 
branch  of  the  superior  maxillary,  and  with  the  supra-orbital 
nerve. 

The  posterior  auricular  nerve  is  a  branch  of  the  facial;  taking 
its  origin  at  the  stylo-mastoid  foramen,  it  ascends  in  front  of  the 
mastoid  process  to  the  back  of  the  ear,  and  divides  into  an  anterior 
and  a  posterior  branch.  The  anterior  branch  (auricular)  is  dis- 
tributed to  the  retrahens  aurem  and  to  the  pinna.  The  posterior 
branch  (occipital)  communicates  with  the  auricularis  magnus 
nerve,  and  is  distributed  to  the  occipito-frontalis. 


118  THE   DISSECTOR. 

The  auricularis  magnus  nerve,  derived  from  the  cervical 
plexus,  divides  below  the  ear  into  branches,  which  are  distributed 
to  the  back  of  the  pinna ;  and  a  mastoid  branch,  which  commu- 
nicates with  the  preceding  nerve,  and  is  distributed  to  the  integu- 
ment over  the  mastoid  process. 

The  occipitalis  minor  nerve,  also  a  branch  of  the  cervical  plexus, 
reaches  the  occiput  at  the  posterior  border  of  the  sterno-mastoid 
muscle,  and  mounting  the  back  of  the  head,  sends  branches  to. the 
occipito-frontalis  and  attollens  aurem  (auricular  branch),  com- 
municates with  the  posterior  auricular  nerve,  and  with  the  occipi- 
talis major. 

The  occipitalis  major  nerve,  a  branch  of  the  posterior  divi- 
sion of  the  second  cervical,  pierces  the  trapezius  muscle  close 
to  the  occipital  artery,  and  lies  by  the  side  of  that  vessel.  Soon 
after  its  emergence  from  the  trapezius,  it  receives  a  branch  from 
the  third  cervical,  and  divides  into  numerous  branches,  which  are 
distributed  to  the  occipito-frontalis  and  integument  as  far  as  the 
summit  of  the  head.  It  communicates  with  the  occipitalis  minor 
nerve,  and  sends  an  auricular  branch  to  the  back  of  the  ear. 

The  student  may  now  open  the  skull,  and  examine  the  contents  of  that 
cavity ;  for  this  purpose  the  brain  must  be  removed.  He  will  find  in- 
structions for  conducting  this  operation  in  Chapter  IV.,  which  is  devoted 
to  the  anatomy  of  the  brain  and  spinal  cord. 

After  the  brain  and  spinal  cord  have  been  studied,  the  dissector  may 
return  to  the  anatomy  of  the  face.  If  he  be  studying  the  right  side  of  the 
face,  an  incision  should  be  made  from  the  front  of  the  ear  along  the  ramus 
of  the  lower  jaw  to  its  angle,  and  thence  onwards  along  the  margin  of  the 
jaw  to  the  chin.  The  integument  should  be  raised  with  care,  and  towards 
the  middle  line.  If  the  student  have  the  left  side  of  the  face,  he  should 
carry  an  incision  from  the  middle  line  of  the  forehead  along  the  ridge  of 
the  nose,  the  upper  and  the  lower  lip,  to  the  chin,  and  then  backward 
along  the  lower  jaw,  dissecting  the  flap  from  the  middle  line  to  the  ear. 
The  muscles  may  then  be  made  clear  by  the  removal  of  the  cellular  tissue 
and  fat ;  in  dissecting  them  they  should  be  put  gently  on  the  stretch,  and 
cleaned  in  the  direction  of  their  fibres. 

3.    Orbital  Group. — Orbicularis  palpebrarum, 

Corrugator  supercilii, 

Tensor  tarsi. 

The  ORBICULARIS  PALPEBRARUM  is  a  sphincter  muscle,  sur- 
rounding the  orbit  and  eyelids.  It  arises  from  the  internal  angu- 
lar process  of  the  frontal  bone,  from  the  nasal  process  of  the 
superior  maxillary,  and  from  a  short  tendon  (tendo  oculi)  which 
extends  between  the  nasal  process  of  the  superior  maxillary  bone, 
and  the  inner  extremities  of  the  tarsal  cartilages  of  the  eyelids. 
The  fibres  encircle  the  orbit  and  eyelids,  forming  a  broad  and 
thin  muscular  plane,  which  is  inserted  into  the  lower  border  of 
the  tendo  oculi,  and  into  the  nasal  process  of  the  superior  maMil- 
lary  bone.  That  portion  of  the  muscle  which  occupies  the  eye- 


TENSOR  TARSI.  119 

lids  (ciliaris)  is  composed  of  fibres,  which  are  thin  and  pale,1  and 
possess  an  involuntary  action.  The  tendo  oculi,  in  addition  to 
its  insertion  into  the  nasal  process  of  the  superior  maxillary 
bone,  sends  a  process  inwards,  which  expands  over  the  lachrymal 
sac,  and  is  attached  to  the  ridge  of  the  lachrymal  bone  :  this  is 
the  reflected  aponeurosis  of  the  tendo  oculi. 

The  CORRUGATOR  SUPERCILII  is  a  small,  narrow,  and  pointed 
muscle,  situated  immediately  above  the  orbit  and  beneath  the 
upper  segment  of  the  orbicularis  palpebrarum.  It  arises  from 
the  inner  extremity  of  the  superciliary  ridge,  and  is  inserted  into 
the  under  surface  of  the  orbicularis  palpebrarum  at  a  point  cor- 
responding with  the  middle  of  the  superciliary  arch. 

The  TENSOR  TARSI  (Homer's9  muscle)  is  a  thin  plane  of  mus- 
cular fibres,  about  three  lines  in  breadth  and  six  in  length.  It 
is  best  dissected  by  separating  the  eyelids  from  the  eye,  and 
turning  them  over  the  nose  without  disturbing  the  tendo  oculi ; 
then  dissect  away  the  small  fold  of  mucous  membrane  called 
plica  semilunaris,  and  some  loose  cellular  tissue  under  which  the 
muscle  is  concealed.  It  arises  from  the  orbital  surface  of  the 
lachrymal  bone,  and  passing  across  the  lachrymal  sac,  divides 
into  two  slips,  which  are  continuous  with  the  margin  of  the 
ciliaris  along  the  edges  of  the  lids,3  some  few  of  its  fibres  being 
attached  to  the  lachrymal  canals  as  far  as  the  puncta. 

ACTIONS. — The  palpebral  portion  of  the  orbicularis  [ciliaris]  acts  invol- 
untarily in  closing  the  lids,  and  from  the  greater  curve  of  the  upper  lid, 
upon  that  principally.  The  entire  muscle  acts  as  a  sphincter,  drawing  at 
the  same  time,  by  means  of  its  osseous  attachment,  the  integument  and 
lids  inwards  towards  the  nose.  The  corrugatores  superciliorum  draw  the 
eyebrows  downwards  and  inwards,  and  produce  the  vertical  wrinkles  of 
the  forehead.  The  tensor  tarsi,  or  lachrymal  muscle,  is  an  auxiliary  to 
the  orbicularis,  and  draws  the  extremities  of  the  lachrymal  canals  in- 
wards, so  as  to  place  the  puncta  in  the  best  position  for  receiving  the 
tears.  It  serves  also  to  keep  the  lids  in  relation  with  the  surface  of  the 
eye,  and  compresses  the  lachrymal  sac.  Dr.  Horner  is  acquainted  with 
two  persons  who  have  the  voluntary  power  of  drawing  the  lids  inwards 
by  these  muscles  so  as  to  bury  the  puncta  in  the  angle  of  the  eye. 

4.  Nasal  Group. — Pyramidal  is  nasi, 
Compressor  nasi, 
Dilatator  naris, 
Depressor  ala3  nasi. 

1  Mr.  Haynes  Walton  has  shown  that  the  margin  of  the  ciliaris  is 
thick,  and  its  fibres  redder  than  the  rest  of  the  ciliary  muscle ;  further- 
more, that  its  thickness  is  augmented  by  the  addition  of  the  tensor  tarsi 
muscle.     This  portion  of  the  muscle  he  conceives  to  be  the  agent  in  the 
production  of  Entropium. — Med.  Times  and  Gazette,  May,  1852. 

2  W.  E.  Horner,  M.  D.,  Professor  of  Anatomy  in  the  University  of  Penn- 
sylvania,,   The  notice  of  this  muscle  is  contained  in  a  work  published  in 
Philadelphia  in  1827,  entitled  "  Lessons  in  Practical  Anatomy." 

*  Mr.  Hayiies  Walton,  loc.  cit. 


120 


THE   DISSECTOR. 


Fig.  34. 


The  PYRAMID ALIS  NASi  is  a  small  pyramidal  slip  of  muscular 
fibres  sent  downwards  upon  the 
bridge  of  the  nose  by  the  occipito- 
frontalis.  It  is  inserted  into  the 
tendinous  expansion  of  the  compres- 
sores  nasi. 

The  COMPRESSOR  NASI  is  a  thin 
and  triangular  muscle  ;  it  arises  by 
its  apex  from  the  canine  fossa  of  the 
superior  maxillary  bone,  and  spreads 
out  upon  the  side  of  the  nose  into  a 
thin  tendinous  expansion,  which  is 
continuous  across  its  ridge  with  the 
muscle  of  the  opposite  side.  It  is 
connected  at  its  origin  with  a  mus- 
cular fasciculus  which  is  attached  to 
the  nasal  process  of  the  superior 
maxillary  bone  immediately  below 
the  origin  of  the  levator  labii  supe- 
rioris  alaeque  nasi.  This  muscular 
slip  was  termed  by  Albinus  mus- 
cuhis  anomahis,  from  its  attachment 
to  the  bone  by  both  ends ;  and  by 
Santorini,  musculus  rhomboideus. 

The  DILATATOR  NARIS  is  a  thin 
and  indistinct  muscular  apparatus 
expanded  upon  the  ala  of  the  nos- 
tril, and  consisting  of  an  anterior 
and  posterior  slip.  The  anterior 

slip  (levator  proprius  alae  nasi  anterior)  arises  from  the  upper 
border  and  surface  of  the  alar  cartilage,  and  is  inserted  into 
the  integument  of  the  border  of  the  nostril.  The  posterior  slip 
(levator  ala3  nasi  posterior)  arises  from  the  nasal  process  of  the 
superior  maxillary  bone  and  from  the  sesamoid  cartilages,  and  is 
inserted  into  the  integument  of  the  border  of  the  nostril  for  the 
posterior  half  of  its  extent. 

The  dilatator  naris  muscle  is  difficult  of  dissection,  from  the  close 
adhesion  of  the  integument  to  the  nasal  cartilages. 

The  DEPRESSOR  AL^E  NASI  (myrtiformis)  is  brought  into  view  by 
drawing  upwards  the  upper  lip  and  raising  the  mucous  membrane. 
It  arises  from  the  superior  maxillary  bone  in  front  of  the  roots 
of  the  second  incisor  and  canine  teeth  (myrtiform  fossa),  and 
passes  upwards  and  inwards  to  be  inserted  into  the  posterior 
part  of  the  columna  and  ala  nasi.  It  is  closely  connected  with 
the  deep  surface  of  the  orbicularis. 


REPRESENTS  THE  MUSCLES  OP 
THE  NASAL  REGION,  WITH  SOME 
OF  THOSE  OF  THE  LIP. — 1.  Pyra- 
midalis  nasi.  2.  Levator  labii 
superioris  alacque  nasi.  3.  Com- 
pressor naris.  4.  Levator  pro- 
prius alee  nasi  anterior.  5.  Leva- 
tor  proprius  alas  nasi  posterior. 
6.  Depressor  alae  nasi.  7.  Orbi- 
cularis. 7*.  Naso-labialis. 


MUSCLES   OF   THE   NOSE.  121 

ACTIONS. — The  pyramidalis  nasi,  as  a  point  of  attachment  of  the  occi- 
pito-frontalis,  assists  that  muscle  in  its  action  :  it  also  draws  down  the 
inner  angle  of  the  eyebrow,  and  by  its  insertion  fixes  the  aponeurosis  of 
the  compressores  nasi,  and  tends  to  elevate  the  nose.  The  compressores 
nasi  appear  to  act  in  expanding  rather  than  in  compressing  the  nares  ; 
hence  probably  the  compressed  state  of  the  nares  from  paralysis  of  these 
muscles  in  the  last  moments  of  life,  or  in  compression  of  the  brain.  The 
dilatator  naris  is  a  dilator  of  the  nostril,  and  the  depressor  al»  nasi 
draws  downwards  both  the  ala  and  columna  of  the  nose,  the  depression 
of  the  latter  being  assisted  by  the  naso-labialis. 

5.   Superior  Labial  Group. — 

Orbicularis  oris, 

Levator  labii  superioris  alaeque  nasi, 

Levator  labii  superioris  proprius, 

Levator  anguli  oris, 

Zygoraaticus  major, 

Zygomaticus  minor. 

The  ORBICULARIS  ORIS  is  a  sphincter  muscle,  completely  sur- 
rounding the  mouth,  and  possessing  consequently  neither  origin 
nor  insertion.  It  is  composed  of  two  thick  semicircular  planes 
of  fibres,  which  embrace  the  rima  of  the  mouth,  and  interlace  at 
their  extremities,  where  they  are  continuous  with  the  fibres  of 
the  buccinator,  and  of  the  other  muscles  connected  with  the 
angle  of  the  mouth.  The  upper  segment  is  attached  by  means 
of  a  small  muscular  fasciculus  (naso-labialis)  to  the  columna  of 
the  nose ;  and  other  fasciculi  connected  with  both  segments,  and 
attached  to  the  maxillary  bones,  are  termed  "accessorii." 

The  LEVATOR  LABII  SUPERIORIS  ALAEQUE  NASI  is  a  thin  triangu- 
lar muscle ;  it  arises  from  the  upper  part  of  the  nasal  process  of 
the  superior  maxillary  bone ;  and,  becoming  broader  as  it  de- 
scends, is  inserted  by  two  distinct  portions  into  the  ala  of  the 
nose  and  upper  lip. 

The  LEVATOR  LABII  SUPERIORIS  PROPRIUS  is  a  thin  quadrilateral 
muscle  ;  it  arises  from  the  lower  border  of  the  orbit,  and,  passing 
obliquely  downwards  and  inwards,  is  inserted  into  the  integu- 
ment of  the  upper  lip,  its  deep  fibres  being  blended  with  those 
of  the  orbicularis. 

The  LEVATOR  ANGULI  ORIS  arises  from  the  canine  fossa  of  the 
superior  maxillary  bone,  and  passes  outwards  to  be  inserted  into 
the  angle  of  the  mouth,  intermingling  its  fibres  with  those  of  the 
orbicularis,  zygomatici,  and  depressor  anguli  oris. 

The  ZYGOMATIC  muscles  are  two  slender  fasciculi  of  fibres  which 
arise  from  the  malar  bone,  and  are  inserted  into  the  angle  of  the 
mouth,  where  they  are  continuous  with  the  other  muscles  attached 
to  this  part.  The  zygomaticus  minor  is  situated  in  front  of  the 
major,  and  is  continuous  at  its  insertion  with  the  levator  labii 
superioris  proprius  :  it  is  not  unfrequently  wanting. 
11 


THE   DISSECTOR. 

ACTIONS. — The  orbicularis  oris  produces  the  direct  closure  of  the  lips 
by  means  of  its  continuity,  at  the  angles  of  the  mouth,  with  the  fibres 
of  the  buccinator.  When  acting  singly  in  the  forcible  closure  of  the 
mouth,  the  integument  is  thrown  into  wrinkles,  in  consequence  of  its 
firm  connection  with  the  surface  of  the  muscle  ;  its  naso-labial  fascicu- 
lus draws  downwards  the  columna  nasi.  The  levator  labii  superioris 
alseque  nasi  lifts  the  upper  lip  with  the  ala  of  the  nose,  and  expands  the 
opening  of  the  nares.  The  levator  labii  superioris  proprius  is  the  proper 
elevator  of  the  upper  lip  ;  acting  singly,  it  draws  the  lip  a  little  to  one  side. 
The  levator  anguli  oris  lifts  the  angle  of  the  mouth  and  draws  it  inwards, 
while  the  zygomatici  pull  it  upwards  and  outwards,  as  in  laughing. 

6.  Inferior  Labial  Group. — 

Depressor  labii  inferioris, 
Depressor  anguli  oris, 
Levator  labii  inferioris. 

The  DEPRESSOR  LABII  INFERIORIS  (quadratus  menti),  arises  from 
the  oblique  line  by  the  side  of  the  symphysis  of  the  lower  jaw, 
and  passing  upwards  and  inwards,  is  inserted  into  the  orbicularis 
muscle  and  integument  of  the  lower  lip. 

The  DEPRESSOR  ANGULI  ORIS  (triangularis  oris),  is  a  triangular 
plane  of  muscle  arising  by  a  broad  base  from  the  external  oblique 
ridge  of  the  lower  jaw,  and  inserted  by  its  apex  into  the  angle 
of  the  mouth,  where  it  is  continuous  with  the  levator  anguli  oris 
and  zygomaticus  major,  and  with  a  subcutaneous  muscle  called 
risorius  Santorini.  The  risorius  Santorini  arises  by  two  or  three 
fasciculi  from  the  fascia  covering  the  masseter  muscle,  and  is  in- 
serted \r\iQ  the  angle  of  the  mouth. 

The  LEVATOR  LABII  INFERIORIS  (levator  menti),  is  a  small 
conical  slip  of  muscle  arising  from  the  incisive  fossa  of  the  lower 
jaw,  and  inserted  into  the  integument  of  the  chin.  It  is  in  rela- 
tion with  the  mucous  membrane  of  the  mouth,  with  its  fellow, 
and  with  the  depressor  labii  inferioris. 
T.  Maxillary  Group. — Masseter, 

Buccinator, 
Temporalis, 
Pterygoideus  externus, 
Pterygoideus  internus. 

Before  proceeding  to  the  dissection  of  the  masseter  muscle,  the  parotid 
gland,  which  overlaps  and  partly  conceals  the  muscle  and  sends  its  ex- 
cretory duct  across  it,  should  be  examined.  The  gland  is  bound  down 
by  a  strong  fascia,  which  may  be  removed. 

The  PAROTID  GLAND  (?tapa,  near,  ov$,  iT'oj,  the  ear),  is  the 
largest  of  three  salivary  glands  situated  on  each  side  of  the  face 
in  the  neighborhood  of  the  mouth.  The  parotid,  as  its  name 
implies,  is  placed  immediately  in  front  of  the  external  ear,  ex- 
tends superficially  for  a  short  distance  over  the  masseter  muscle, 
and  deeply  behind  the  ramus  of  the  lower  jaw.  It  reaches  in- 


MASSETER.  123 

feriorly  to  below  the  level  of  the  angle  of  the  jaw,  and  poste- 
riorly to  the  mastoid  process,  slightly  overlapping  the  insertion 
of  the  sterno-mastoid  muscle.  Embedded  in  its  substance,  are 
the  external  carotid  artery,  the  temporo-inaxillary  vein,  and  facial 
nerve ;  emerging  from  its  anterior  border,  the  transverse  facial 
artery  and  branches  of  the  facial  nerve ;  and  above,  the  temporal 
artery  and  auriculo-temporal  nerve. 

The  duct  of  the  parotid  gland  (Stenon's  duct),  about  two 
inches  in  length,  and  about  the  diameter  of  a  crow's-quill,  issues 
from  the  anterior  part  of  the  gland,  just  below  the  zygoma,  and 
crosses  the  masseter  muscle ;  it  then  curves  inwards  over  the  an- 
terior border  of  the  muscle,  and  pierces  the  buccinator  opposite 
the  second  molar  tooth  of  the  upper  jaw;  its  opening  in  the 
mouth  being  indicated  by  a  prominent  papilla.  A  small  glan- 
dular appendage,  the  soda  parotidis,  is  connected  with  the  upper 
part  of  the  duct  on  the  masseter  muscle. 

Structure. — The  salivary  are  conglomerate  glands,  consisting  of  lobes, 
which  are  made  up  of  polyhedral  lobules,  and  these  of  smaller  lobules. 

The  smallest  lobule  is  apparently  composed  of  granules,  which  are 
minute  caeca!  pouches,  formed  by  the  dilatation  of  the  extreme  ramifica- 
tions of  the  ducts.  These  minute  ducts  unite  to  form  lobular  ducts,  and 
the  lobular  «ducts  constitute  by  their  union  a  single  excretory  duct.  The 
caecal  pouches  are  connected  by  cellular  tissue,  so  as  to  form  a  minute 
lobule;  the  lobules  are  held  together  by  a  more  condensed  cellular  layer; 
and  the  larger  lobes  are  enveloped  by  a  dense  fibrous  capsule,  which  is 
firmly  attached  to  the  deep  cervical  fascia.  The  submaxillary  and  sub- 
lingual  glands  are  looser  in  structure,  and  their  lobules  are  larger  than 
those  of  the  parotid  gland. 

The  duct  of  the  parotid  gland  may  now  be  cut  across,  when  the 
small  size  of  its  area,  as  compared  with  the  thickness  of  its  wall,  will  be 
observed.  The  gland  may  then  be  drawn  back,  or  so  much  of  it  removed 
as  shall  interfere  with  the  examination  of  the  masseter  muscle. 

The  MASSETER  (paarfdopai,  to  chew),  is  a  short,  thick,  and  some- 
what quadrilateral  muscle,  composed  of  two  planes  of  fibres,  su- 
perficial and  deep.  The  superficial  layer  arises  by  a  strong 
aponeurosis  from  the  tuberosity  of  the  superior  maxillary  bone, 
the  lower  border  of  the  ma*lar  bone,  and  the  zygoma,  and  passes 
backwards  to  be  inserted  into  the  ramus  and  angle  of  the  inferior 
maxilla.  The  deep  layer  arises  from  the  posterior  part  of  the 
zygoma,  and  passes  forwards,  to  be  inserted  into  tfte  upper  half 
of  the  ramus.  This  muscle  is  tendinous  and  muscular  in  its 
structure. 

The  buccinator  muscle  is  in  a  great  measure  concealed  from  view  by  a 
lobulated  mass  of  fat,  which  fills  up  the  hollow  in  front  of  the  masseter. 
Through  this  mass  of  fat  the  duct  of  the  parotid  gland  makes  its  way. 
The  fat  is  now  to  be  removed  in  order  to  bring  the  muscle  into  view ; 
and  the  operation  is  to  be  conducted  with  care;  in  order  to  avoid  disturb- 
ing the  facial  artery  and  vein.  The  muscle  is  invested  by  a  thin  fascia. 


124 


THE   DISSECTOR. 


The  BUCCINATOR  MUSCLE  (bticcina,  a  trumpet),  the  trumpeter's 
muscle,  arises  from  the  alveolar  process  of  the  superior  maxilla, 
from  the  external  oblique  line  of  the  inferior  maxilla  as  far  for- 
ward as  the  second  bicuspid  tooth,  and  from  the  pterygo-maxil- 
lary  ligament.  This  ligament  is  the  raphe  of  union  between  the 
buccinator  and  superior  constrictor  muscle,  and  is  attached  by 
one  extremity  to  the  hamular  process  of  the  internal  pterygoid 
plate,  and  by  the  other  to  the  extremity  of  the  molar  ridge.  The 
fibres  of  the  muscle  converge  towards  the  angle  of  the  mouth, 
where  they  cross  each  other,  the  superior  being  continuous  with 
the  inferior  segment  of  the  orbicularis  oris,  and  the  inferior  with 
the  superior  segment. 

The  next  step  in  the  dissection  necessary  to  display  the  remaining 
muscles  of  this  group  requires  the  section  of  the  zygoma  at  both  extremi- 
ties, and  its  removal,  turning  it  down  with  the  masseter.  This  brings 
into  view  the  lower  part  of  the  temporal  muscle,  which  has  been  already 
described  (page  115).  The  coronoid  process  may  then  be  cut  across  with 
a  saw,  and  drawn  upwards  with  the  tendon  of  the  temporal  muscle.  In 
the  next  place,  that  portion  of  the  ramus  of  the  jaw  bet  ween  its  neck  and 
the  angle  must  be  sawn  through  and  removed,  when  the  two  pterygoid 
muscles  will  become  visible,  and  may  be  dissected.  This  preparation 
will  also  display  the  origin  of  the  buccinator  muscle  from  the  pterygo- 
maxillary  ligament. 


Fig.  35. 


THE  TWO  PTERYGOID  MUSCLES. 
THE  ZYGOMATIC  ARCH  AND  THE 
GREATER  PART  OP  THE  RAMUS  OF 
THE  LOWER  JAW  HAVE  BEEN  RE- 
MOVED IN  ORDER  TO  BRING  THESE 

MUSCLES  INTO  VIEW. — 1.  The  sphe- 
noid origin  of  the  external  pterygoid 
muscle.  2.  Its  pterygoid  origin. 
3.  The  internal  pterygoid  muscle. 


The    EXTERNAL    PTERYGOID    IS 

a  short  and  thick  muscle,  broader 
at  its  origin  than  at  its  insertion. 
It  arises  by  two  heads,  one  from 
the  pterygoid  ridge  on  the  greater 
ala  of  the  sphenoid;  the  other 
from  the  external  pterygoid  plate 
and  tuberosity  of  the  palate  bone. 
The  fibres  pass  backwards  to  be 
inserted  into  the  neck  of  the  lower 
jaw  and  the  interarticular  fibro- 
cartilage.  The  internal  maxillary 
artery  frequently  passes  between 
the  two  heads  of  this  muscle. 


The  external  pterygoid  muscle  must 
now  be  removed,  and  the  head  of  the 
lower  jaw  dislocated  from  its  socket 
and  withdrawn,  for  the  purpose  of 
seeing  the  pterygoideus  internus. 

The  INTERNAL  PTERYGOID  is  a 

thick  quadrangular  muscle.  It 
arises  from  the  pterygoid  fossa  and  descends  obliquely  back- 
wards, to  be  inserted  into  the  ramus  and  angle  of  the  lower  jaw : 


NEEVES   OF   THE   FACE.  125 

it  resembles  the  masseter  in  appearance  and  direction,  and  was 
named  by  Winslow  the  internal  masseter. 

ACTIONS. — The  maxillary  muscles  are  the  active  agents  in  mastication, 
and  form  an  apparatus  beautifully  fitted  for  that  office.  The  buccinator 
circumscribes  the  cavity  of  the  mouth,  and  with  the  aid  of  the  tongue 
keeps  the  food  under  the  immediate  pressure  of  the  teeth.  By  means  of 
its  connection  with  the  superior  constrictor,  it  shortens  the  cavity  of  the 
pharynx  from  before  backwards,  and  becomes  an  important  auxiliary  in 
deglutition.  The  temporal,  the  masseter,  and  the  internal  pterygoid  are 
the  bruising  muscles,  drawing  the  lower  jaw  against  the  upper  with  great 
force.  The  two  latter,  from  the  obliquity  of  their  direction,  assist  the 
external  pterygoid  in  grinding  the  food,  by  carrying  the  lower  jaw  for- 
ward upon  the  upper ;  the  jaw  being  brought  back  again  by  the  deep 
portion  of  the  masseter  and  posterior  fibres  of  the  temporal.  The  whole 
of  these  muscles,  acting  in  succession,  produce  a  rotary  movement  of  the 
teeth  upon  each  other,  which,  with  the  direct  action  of  the  lower  jaw 
against  the  upper,  eflects  the  proper  mastication  of  the  food. 

Vessels  and  Nerves  of  the  Face. 

The  vessels  and  nerves  may  now  be  dissected  on  the  opposite  side  of 
the  face.  The  integument  should  be  removed  with  care,  in  the  manner 
already  pointed  out  for  the  examination  of  the  muscles  (page  118),  and 
the  vessels  and  nerves  sought  for  and  followed  through  their  course. 
As  a  preparatory  step,  the  branches  of  the  facial  nerve  should  be  found 
as  they  issue  from  beneath  the  anterior  border  of  the  parotid  gland,  and 
traced  backwards  through  the  gland  to  their  trunk ;  they  may  then  be 
traced  in  their  distribution  over  the  face. 

The  FACIAL  NERVE  (portio  dura),  the  motor  nerve  of  the  face, 
issues  from  the  cranium  through  the  stylomastoid  foramen,  passes 
forward  through  the  parotid  gland  to  the  ramus  of  the  jaw,  and 
divides  into  two  trunks,  tempora-facial  and  cervico-facial.  These 
trunks  divide  into  numerous  branches  which  escape  from  the 
anterior  border  of  the  parotid  gland  and  are  distributed  in  a 
radiated  manner  over  the  side  of  the  face,  from  the  temple  to 
below  the  lower  jaw ;  on  the  masseter  muscle  the  branches  com- 
municate and  form  loops,  and  the  whole  arrangement  over  the 
side  of  the  face  has  been  termed  pes  anserinus. 

The  branches  of  the  facial  nerve,  at  its  exit  from  the  stylo- 
mastoid foramen,  are  three  in  number,  namely,  the  posterior  auri- 
cular, a  stylo-hyoid  branch  for  the  muscle  of  that  name,  and  a 
digastric  branch  for  the  digastricus. 

The  posterior  auricular  branch  ascends  in  front  of  the  mastoid 
process  to  the  back  of  the  ear,  and  divides  into  an  anterior  or 
auricular,  and  a  posterior  or  occipital  branch.  The  auricular 
branch  communicates  with  the  auricular  branch  of  the  pueumo- 
gastric  nerve,  and  is  distributed  to  the  retrahens  aurem  and  pinna. 
The  occipital  branch  communicates  with  the  auricularis  magnus 
and  occipitalis  minor,  and  is  lost  in  the  occipito-frontalis  muspje 
(page  117). 

11* 


126  THE  DISSECTOR. 

The  stylo-hyoid  branch  supplies  the  stylo-hyoideus  muscle,  and 
communicates  with  the  sympathetic  plexus  of  the  external  carotid 
artery. 

The  digastric  branch  enters  the  posterior  belly  of  the  digastri- 
cus  muscle,  and  communicates  with  the  glosso-pharyngeal  and 
pneumogastric  nerve. 

The  temporo-facial  division,  while  in  the  parotid  gland,  sends 
a  branch  of  communication  along  the  carotid  artery  to  the  auri- 
culo-temporal  nerve,  and  divides  into  temporal,  malar,  and  infra- 
orbital  branches. 

The  temporal  branches,  ascending  over  the  temporal  region, 

Fig.  36. 


THE  DISTRIBUTION  OP  THE  FACIAL  NERVE  AND  THE  BRANCHES  OP  THE  CER- 
VICAL PLEXUS. — 1.  The  facial  nerve,  escaping  from  the  stylo-mastoid  foramen, 
and  crossing  the  ramus  of  the  lower  jaw ;  the  parotid  gland  has  been  removed 
in  order  to  see  the  nerve  more  distinctly.  2.  The  posterior  auricular  branch  ; 
the  digastric  and  stylo-mastoid  filaments  are  seen  near  the  origin  of  this  branch. 
3.  Temporal  branches,  communicating  with  (4)  the  branches  of  the  frontal 
nerve.  5.  Facial  branches,  communicating  with  (6)  the  infra-orbital  nerve.  7. 
Facial  branches,  communicating  with  (8)  the  mental  nerve.  9.  Cervico-facial 
branches,  communicating  with  (10)  the  superficialis  colli  nerve,  and  forming  a 
plexus  (|1)  pver  the  submaxillary  gland.  The  distribution  of  the  branches  of 
the  facial  in  a  radiated  direction  over  the  side  of  the  face  constitutes  the  pes 
anserinus.  12.  The  auricularis  magnus  nerve,  one  of  the  ascending  branches 
of  the  cervical  plexus.  13.  The  occipitalis  minor,  ascending  along  the  posterior 
border  of  the  sterno-mastoid  muscle.  14.  The  superficial  and  deep  descending 
branches  of  the  cervical  plexus.  $5.  The  spinal  accessory  nerve,  giving  off  a 
branch  to  the  external  surface  of  the  trnpezius  muscle.  16.  The  occipitalis 
taajqr  nerve,  the  posterior  branch  of  the  second  cervical  nerve. 


FACIAL   ARTEEY.  12t 

supply  the  attrahens  aurem,  occipito-frontalis,  and  orbicularis 
palpebrarum ;  and  communicate  with  the  supra-orbital  nerve 
and  the  temporal  branch  of  the  superior  maxillary  (page  117). 

The  malar  branches  cross  the  malar  bone  to  the  outer  angle  of 
the  eye,  and  supply  the  orbicularis  palpebrarum,  corrugator 
supercilii,  and  eyelids.  They  communicate  with  the  subcutaneous 
malse  branch  of  the  superior  maxillary  nerve,  and  with  branches 
of  the  ophthalmic  nerve  in  the  eyelids. 

The  infra-orbital  branches  cross  the  masse ter  muscle,  and  are 
distributed  to  the  buccinator,  elevator  muscles  of  the  upper  lip, 
and  orbicularis  oris.  They  communicate  with  the  terminal 
branches  of  the  infra-orbital  nerve,  the  infra-trochlear  and  nasal 
nerve.  Two  or  more  of  these  branches  are  found  by  the  side  of 
Stenon's  duct. 

The  cervico-facial  division,  smaller  than  the  temporo-facial, 
communicates  in  the  parotid  gland  with  the  auricularis  magnus 
nerve,  and  divides  into  branches  which  admit  of  arrangement 
into  three  sets  :  buccal,  supra-maxillary,  and  infra-maxillary. 

The  buccal  branches  pass  forwards  across  the  masseter  muscle 
towards  the  mouth,  and  distribute  branches  to  the  orbicularis 
oris  and  buccinator.  They  communicate  with  the  branches  of 
the  temporo-facial,  and  with  the  buccal  branch  of  the  inferior 
maxillary  nerve. 

The  supra-maxillary  branches  are  destined  to  the  muscles  of 
the  lower  lip,  and  take  their  course  along  the  body  of  the  lower 
jaw.  They  have  a  plexiform  communication  with  the  inferior 
dental  nerve  beneath  the  depressor  anguli  oris. 

The  infra-maxillary  branches  (subcutanei  colli)  take  their 
course  below  the  lower  jaw,  pierce  the  deep  cervical  fascia,  and 
are  distributed  to  the  platysma  and  integument.  They  commu- 
nicate with  the  superficialis  colli  nerve. 

The  facial  nerve  has  been  called  the  sympatheticus  minor,  on  account  of 
its  numerous  communications  with  other  nerves.  Thus,  within  the 
cranium  it  communicates  with  the  auditory  nerve,  spheno-palatine  gan- 
glion, and  pneumogastric  nerve  ;  at  its  exit,  with  the  glosso-pharyngeal, 
sympathetic,  and  cervical  nerves  ;  and  on  the  face  with  the  three  divi- 
sions of  the  fifth  nerve. 

The  FACIAL  ARTERY,  a  branch  of  the  external  carotid,  enters 
upon  the  face  by  curving  around  the  body  of  the  low«r  jaw  at 
the  anterior  inferior  angle  of  the  masseter  muscle.  It  then  passes 
forwards  in  a  more  or  less  tortuous  course  to  the  angle  of  the 
mouth,  and  ascends  by  the  side  of  the  nose  to  the  inner  angle  of 
the  eye,  where  it  is  named  the  angular  artery ;  it  terminates  by 
inosculating  with  the  nasal  and  frontal  branches  of  the  ophthal- 
mic artery.  In  its  course  over  the  jaw  it  is  covered  by  the 
platysma  myoides,  and  at  the  angle  of  the  mouth  by  the  depres- 


128  THE   DISSECTOR. 

sor  anguli  oris  and  zygomatie  muscles.  It  rests  on  the  buccina- 
tor and  elevator  muscles  of  the  lip. 

The  branches  of  the  facial  artery  are,  twigs  to  the  masseter 
muscle  (masseteric),  inferior  labial,  inferior  coronary,  superior 
coronary,  and  lateral  nasal. 

The  inferior  labial  branch  passes  forwards  beneath  the  depres- 
sor anguli  oris  muscle,  and  is  distributed  to  the  muscles  of  the 
lower  lip,  inosculating  with  the  labial  branch  of  the  inferior 
dental,  and  with  the  inferior  coronary. 

The  inferior  coronary  branch  is  given  off  at  the  angle  of  the 
mouth,  and  passes  inwards  near  the  edge  of  the  lower  lip,  lying 
between  the  orbicularis  and  the  mucous  membrane  :  it  inoscu- 
lates with  its  fellow  of  the  opposite  side. 

The  superior  coronary  branch,  arising  close  to,  or  in  common 
with,  the  preceding,  takes  its  course  in  the  same  manner  along 
the  upper  lip,  inosculating  with  its  fellow  of  the  opposite  side. 
At  the  middle  of  the  lip  it  sends  a  small  branch  upwards  to  the 
septum  of  the  nose  (artery  of  the  septum). 

The  lateral  nasal  branch  is  given  off  near  the  ala  nasi,  and 
passes  beneath  the  levator  labii  superioris  alaeque  nasi,  to  be  dis- 
tributed to  the  nose.  It  inosculates  with  the  nasal  branch  of  the 
ophthalmic  artery. 

The  FACIAL  VEIN  commences  at  the  inner  angle  of  the  eye, 
where,  under  the  name  of  angular  vein,  it  receives  the  frontal 
vein  from  the  forehead ;  the  frontal  veins  of  opposite  sides  being 
united  across  the  bridge  of  the  nose  by  a  transverse  branch.  The 
facial  vein  passes  outwards  beneath  the  zygomatic  muscles  to  the 
anterior  border  of  the  masseter  muscle,  along  which  it  descends 
to  the  lower  jaw,  where  it  joins  the  facial  artery.  Passing  over 
the  jaw  it  pierces  the  deep  cervical  fascia,  and  terminates  in  the 
internal  jugular  vein. 

The  TRANSVERSE  FACIAL  ARTERY,  a  branch  of  the  temporal 
artery,  emerges  from  beneath  the  anterior  border  of  the  parotid 
gland,  and  runs  transversely  across  the  face  a  little  above  Stenon's 
duct.  It  supplies  the  muscles  in  its  course,  and  inosculates  with 
the  facial  and  infraorbital  artery. 

ANATOMY  OF  THE  ORBIT. 

To  open  the  orbit  (the  calvaria  and  brain  having  been  removed)  the 
frontal  bone  must  be  sawn  through  at  the  inner  extremity  of  the  orbital 
ridge  ;  and  externally,  at  its  outer  extremity.  The  roof  of  the  orbit  may 
then  be  comminuted  with  the  hammer ;  a  process  easily  performed,  on 
account  of  the  thinness  of  the  orbital  plate  of  the  frontal  bone  and  lesser 
wing  of  the  sphenoid.  The  superciliary  portion  of  the  orbit  may  now  be 
driven  forwards  by  a  smart  blow,  and  the  broken  fragments  of  the  roof 
of  the  orbit  removed.  The  periosteum  will  then  be  exposed  unbroken 
and  undisturbed. 


PERIOSTEUM — MUSCLES.  129 

The  PERIOSTEUM  is  a  moderately  thick  white  membrane,  only 
slightly  connected  with  the  surface  of  the  bones  of  the  orbit  on 
account  of  their  smoothness  and  density,  but  firmly  at  the  different 
sutures,  or  at  the  points  of  transit  of  vessels  and  nerves.  It  is 
continuous  through  the  optic  foramen  and  sphenoidal  fissure  with 
the  dura  mater,  and  at  the  margins  of  the  orbit  with  the  pericra- 
nium and  periosteum  of  the  face. 

Remove  the  periosteum  from  the  whole  of  the  upper  surface  of  the  ex- 
posed orbit,  and  the  muscles,  vessels,  and  nerves  may  then  be  examined. 

The  contents  of  the  orbit  are,  1st.  The  globe  of  the  eye  appended  to  the 
extremity  of  the  optic  nerve.  2d.  The  six  muscles  which  move  the  eye- 
ball, four  recti,  two  obliqui,  and  the  elevator  muscle  of  the  upper  eyelid. 
3d.  The  ophthalmic  artery  with  its  branches.  4th.  The  ophthalmic  vein 
with  its  tributaries.  5th.  The  nerves,  which  consist  of  three  branches  of 
the  ophthalmic — frontal,  lachrymal,  and  nasal ;  the  third,  fourth,  and 
sixth,  to  the  muscles  ;  and  the  ciliary  ganglion  with  its  branches.  6th. 
The  lachrymal  gland. 

In  the  middle  line  is  the  levator  palpebrse  muscle,  and  resting  upon  it 
the  frontal  nerve,  with  its  accompanying  artery,  the  supra-orbital.  To 
the  inner  side  is  the  obliquus  superior,  and  running  along  its  border  the 
fourth  nerve  posteriorly,  and  the  infra-trochlear  branch  in  front.  To  the 
outer  side  is  the  upper  border  of  the  external  rectus  supporting  the 
lachrymal  artery  and  nerve,  and  in  front  the  lachrymal  gland. 

If  the  levator  palpebrae  muscle,  and  with  it  the  frontal  nerve  and  supra- 
orbital  artery,  be  divided  through  the  middle  and  turned  aside,  the  su- 
perior rectus  will  be  seen  occupying  the  middle  place  ;  and  if  the  obliquus 
superior  be  also  divided  and  its  ends  thrown  aside,  the  upper  margin  of 
the  internal  reetus  will  occupy  the  inner  side  supporting  the  infra-trochlear 
nerve. 

Next  divide  the  superior  rectus  through  the  middle,  and  draw  its  ends 
asunder,  in  doing  which  a  branch  of  the  third  nerve  maybe  seen  entering 
its  under  surface,  and  a  third  plane  will  be  brought  into  view.  This  re- 
quires to  be  freed  of  a  large  quantity  of  fat,  before  the  structures  situated 
in  it  can  be  fully  seen.  The  student  must  work  cautiously  and  unweari- 
edly,  until  he  has  removed  every  particle  of  this  fat,  which  is  not  difficult 
to  do  from  its  being  contained  in  areolae  of  loose  cellular  tissue. 

In  the  middle  line  he  will  now  perceive  the  optic  nerve,  crossed  from 
without  inwards  by  the  ophthalmic  artery  and  nasal  nerve,  and  having 
to  its  outer  side  the  ascending  branch  of  the  third  nerve,  the  ciliary  gan- 
glion with  its  branches,  the  ciliary  arteries,  and  a  little  more  externally, 
in  contact  with  the  external  rectus  muscle,  the  sixth  nerve. 

Next  divide  the  optic  nerve  through  its  middle,  and  draw  it  forwards, 
when  a  layer  will  be  observed,  which  is  formed  by  the  inferior  rectus 
muscle  supporting  the  long  branch  of  the  third  nerve  in  the  middle  line  ; 
and  in  front,  the  inferior  oblique  muscle  connected  with  the  globe  of  the 
eye. 

The  MUSCLES  of  the  orbit  are  seven  in  number;  namely — 
Levator  palpebrse,  Rectus  externus, 

Rectus  superior,  Obliquus  superior, 

Rectus  inferior,  Obliquus  inferior. 

Rectus  internus, 


130  THE   DISSECTOR. 

The  dissection  of  the  muscles  of  the  orbit  may  be  facilitated  by  drawing 
the  globe  of  the  eye  forwards  ;  or,  if  it  be  desired,  the  muscles  may  be 
made  tense  by  injecting  the  globe  of  the  eye  with  tallow  or  wax.  For 

Fig.  37.  THE    MUSCLES   OP   THE  EYE- 

BALL ;    THE  VIEW  IS  TAKEN  FROM 
THE    OUTER    SIDE    OP    THE    RIGHT 

ORBIT. — 1.  A  small  fragment  of 
the  sphenoid  bone  around  the  en- 
trance of  the  optic  nerve  into  the 
orbit.  2.  The  optic  nerve.  3. 
The  globe  of  the  eye.  4.  The 
levator  palpebrae  muscle.  5.  The 
superior  oblique  muscle.  6.  Its 
cartilaginous  pulley.  7.  Its  re- 
flected tendon.  8.  The  inferior 
oblique  muscle,  the  small  square 
knob  at  its  commencement  is  a 
piece  of  its  bony  origin  broken  off.  9.  The  superior  rectus.  10.  The  internal 
rectus  almost  concealed  by  the  optic  nerve.  11.  Part  of  the  external  rectus, 
showing  its  two  heads  of  origin.  12.  The  extremity  of  the  external  rectus  at 
its  insertion  ;  the  intermediate  portion  of  the  muscle  having  been  removed.  13. 
The  inferior  rectus.  14.  The  tunica  albuginea,  formed  by  the  expansion  of  the 
tendons  of  the  four  recti. 

this  purpose  a  probe  should  be  pushed  along  the  optic  nerve,  so  as  to 
break  down  the  cribriform  plate  of  the  sclerotic  coat,  and  an  injecting 
pipe  introduced  into  the  neurilemma  of  the  nerve.  By  similar  means 
the  globe  of  the  eye  may  be  distended  with  air. 

The  LEVATOR  PALPEBR^E  is  a  long,  thin,  and  triangular  muscle, 
situated  in  the  upper  part  of  the  orbit  on  the  middle  line;  it 
arises  from  the  upper  margin  of  the  optic  foramen,  and  from  the 
fibrous  sheath  of  the  optic  nerve,  and  is  inserted  into  the  upper 
border  of  the  superior  tarsal  cartilage. 

The  RECTUS  SUPERIOR  (attollens)  arises  from  the  upper  margin 
of  the  optic  foramen,  and  from  the  fibrous  sheath  of  the  optic 
nerve,  and  is  inserted  into  the  upper  surface  of  the  globe  of  the 
eye  at  a  point  somewhat  more  than  three  lines  from  the  margin 
of  the  cornea. 

The  RECTUS  INFERIOR  (depressor)  arises  from  the  inferior  mar- 
gin of  the  optic  foramen  by  a  tendon  (ligament  of  Zinn)  which 
is  common  to  it,  the  internal  and  the  external  rectus,  and  from  the 
fibrous  sheath  of  the  optic  nerve;  it  is  inserted  into  the  inferior 
surface  of  the  globe  of  the  eye,  a  little  more  than  two  lines  from 
the  margin  of  the  cornea. 

The  RECTUS  INTERNUS  (adductor),  the  thickest  and  shortest  of 
the  straight  muscles,  arises  from  the  common  tendon  and  from 
the.  fibrous  sheath  of  the  optic  nerve,  and  is  inserted  into  the  inner 
surface  of  the  globe  of  the  eye  at  two  lines  from  the  margin  of 
the  cornea. 

The  RECTUS  EXTERNUS  (abductor),  the  longest  of  the  straight 


OBLIQUUS   SUPERIOR — OBLIQUUS   INFERIOR.          131 

muscles,  arises  by  two  distinct  heads,  one  from  the  common 
tendon,  the  other,  with  the  origin  of  the  superior  rectus,  from 
the  margin  of  the  optic  foramen  ;  the  nasal  third  and  sixth  nerves 
passing  between  its  heads.  It  is  inserted  into  the  outer  surface 
of  the  globe  of  the  eye,  a  little  more  than  two  lines  from  the 
margin  of  the  cornea. 

The  recti  muscles  present  several  characters  which  are  common  to  all ; 
thus,  they  are  thin,  have  each  the  form  of  an  isosceles  triangle,  bear  the 
same  relation  to  the  globe  of  the  eye,  and  are  inserted  in  a  similar  man- 
ner into  the  sclerotica  at  about  two  lines  from  the  circumference  of  the 
cornea.  The  points  of  difference  relate  to  thickness  and  length ;  the 
internal  rectus  is  the  thickest  and  shortest,  the  external  rectus  the  longest 
of  the  four,  and  the  superior  rectus  the  most  thin.  The  insertion  of  the 
four  recti  muscles  into  the  globe  of  the  eye  forms  a  tendinous  expansion, 
which  is  continued  as  far  as  the  margin  of  the  cornea,  and  is  called  the 
tunica  albugiuea.  ...  . 

The  OBLIQUUS  SUPERIOR  (trochlearis)  is  a  fusiform  muscle 
arising  from  the  margin  of  the  optic  foramen  and  from  the 
fibrous  sheath  of  the  optic  nerve ;  it  passes  forwards  to  the  pul- 
ley beneath  the  internal  angular  process  of  the  frontal  bone ;  its 
tendon  is  then  reflected  beneath  the  superior  rectus  muscle,  to 
the  outer  and  posterior  part  of  the  globe  of  the  eye,  where  it  is 
inserted  into  the  sclerotic  coat  near  the  entrance  of  the  optic 
nerve. 

The  trochlea  or  pulley  of  the  superior  oblique  muscle  is  a  fibro- 
cartilaginous  ring  attached  to  the  depression  beneath  the  internal 
angular  process  of  the  frontal  bone.  The  ring  is  flat,  about  a 
line  in  width,  and  provided  with  a  synovial  membrane,  which  is 
continued  together  with  a  fibrous  sheath,  for  a  short  distance, 
upon  the  tendon.  Sometimes  the  ring  is  supported,  or  in  part 
formed,  by  a  process  of  bone. 

The  OBLIQUUS  INFERIOR,  a  thin  and  narrow  muscle,  arises  from 
the  inner  margin  of  the  superior  maxillary  bone,  immediately 
external  to  the  lachrymal  groove,  and  passes  beneath  the  inferior 
rectus,  to  be  inserted  into  the  outer  and  posterior  part  of  the  eye- 
ball at  about  two  lines  from  the  entrance  of  the  optic  nerve. 

ACTIONS. — The  levator  palpebrae  raises  the  upper  eyelid.  The  four  recti, 
acting  singly,  pull  the  eyeball  in  the  four  directions :  upwards,  down- 
wards, inwards,  and  outwards.  Acting  by  pairs,  they  carry  the  eyeball 
in  the  diagonal  of  these  directions,  viz  :  upwards  and  inwards,  upwards 
and  outwards,  downwards  and  inwards,  or  downwards  and  outwards. 
Acting  all  together,  they  directly  retract  the  globe  within  the  orbit.  The 
superior  oblique  muscle,  acting  alone,  rolls  the  globe  inwards  and  for- 
wards, and  carries  the  pupil  outwards  and  downwards  to  the  lower  and 
outer  angle  of  the  orbit.  The  inferior  oblique  acting  alone,  rolls  the  globe 
outwards  and  backwards,  and  carries  the  pupil  outwards  and  upwards  to 
the  upper  and  outer  angle  of  the  eye.  Both  muscles  acting  together, 
draw  the  eyeball  forwards,  and  give  the  pupil  that  slight  degree  of  ever- 
sion  which  enables  it  to  admit  the  largest  field  of  vision. 


132 


THE  DISSECTOR. 


Nerves  of  the  Orbit. 

The  dissection  of  the  nerves  of  the  orbit  may  be  prosecuted  either  on 
the  same  side  as  the  muscles,  if  the  parts  have  not  been  too  much  dis- 
turbed, or  the  opposite  orbit  may  be  taken  expressly  for  the  purpose. 
The  outer  wall  of  the  orbit  should  be  broken  away  with  the  chisel  and 
bone-nippers,  to  bring  the  apex  of  the  orbit  well  into  view,  and  the  ante- 
rior clinoid  process  should  also  be  removed.  Furthermore,  a  thin  layer 
of  the  dura  mater  should  be  raised  from  the  side  of  the  sella  turcica,  in 


Fig.  38. 


THE  ORIGIN,  COURSE,  AND  DISTRIBUTION  OP  THE  NERVES  OF  THE  ORBIT. 
THE  PONS  VAROLII,  AND  MEDULLA  OBLONGATA  ARE  IN  OUTLINE,  AND  THE 

HORIZONTAL  PORTION  OF    THE  CAROTID  ARTERY    MARKS  THE   SITUATION    OF    THE 

CAVERNOUS  SINUS. — 1.  The  pons  Varolii.  2.  The  medulla  oblongata.  3.  The 
third  nerve,  arising  from  the  crus  cerebri.  7.  Its  ascending  branch.  8.  Its 
communication  with  the  ciliary  ganglion.  4.  The  fourth  nerve,  arising  from 
the  valve  of  Yieussens,  immediately  below  the  corpora  quadrigemina,  9.  5. 
The  fifth  nerve,  arising  by  two  roots.  10.  The  posterior  root  from  the  corpus 
restiforme.  11.  The  anterior  root  from  the  corpus  pyramidale.  12.  The  Cas- 
serian  ganglion.  13.  Its  ophthalmic  division.  14.  Its  superior  maxillary  divi- 
sion. 15.  Its  inferior  maxillary  division.  16.  The  frontal  branch  of  the 
ophthalmic  nerve.  17.  The  lachrymal  branch.  18.  The  nasal.  19.  Its  com- 
munication with  the  ciliary  ganglion.  20.  Its  ciliary  branches.  21.  The 
infra-trochlear  branch,  given  off  just  as  the  nerve  enters  the  anterior  ethmoidal 
foramen.  6.6.  The  sixth  nerv«,  arising  from  the  corpus  pyramidale.  22.  The 
ciliary  ganglion,  giving  off  ciliary  nerves.  23.  The  outline  of  the  optic  nerve. 
24.  The  internal  carotid  artery.  25.  The  corpus  olivare.  The  arrow  at  3 
marks  the  relative  situation  of  the  four  nerves  of  the  orbit,  as  they  enter  the 
cavernous  sinus.  The  third  is  the  highest,  then  the  fourth,  next  the  ophthal- 
mic division  of  the  fifth,  and  then  the  sixth.  The  arrow  at  6  marks  the  rela- 
tion of  the  six  nerves  as  they  enter  the  sphenoidal  fissure  : — the  three  superior, 
fourth,  frontal,  and  lachrymal  enter  the  orbit  above  the  origin  of  the  levator 
palpebrae ; — three  inferior,  nasal,  third,  and  sixth,  pass  between  the  two  heads 
of  the  external  rectus. 


NERVES   OF   THE   ORBIT. 


133 


order  to  bring  into  view  the  trunks  of  the  nerves  in  their  course  to  the 
orbit,  and  the  parts  situated  in  the  cavernous  sinus. 

The  NERVES  of  the  orbit  are  the  third,  fourth,  first  division  of 
the  fifth,  sixth,  and  the  ophthalmic  or  ciliary  ganglion,  with  its 
branches. 

The  THIRD  NERVE  (motores  oculorum)  pierces  the  dura  mater 
immediately  in  front  of  the  posterior  clinoid  process,  and  pass- 
ing obliquely  forwards  and  downwards,  divides  into  two  branches, 
which  enter  the  orbit  through  the  sphenoidal  fissure,  and  be- 
tween the  two  heads  of  the  external  rectus  muscle. 

The  superior  branch  ascends  and  supplies  the  superior  rectus 
and  levator  palpebrae. 


Fig.  39. 


Fig.  40. 


THE  NERVES  IN  THE  ORBIT  ABOVE 
THE  MUSCLES,  BROUGHT  INTO  VIEW 
BY  REMOVING  THE  RoOP  OF  THE  OR- 
BIT AND  THE  PERIOSTEUM.  —  1.  Fifth 
2.  Ophthalmic  branch  of  same 
3.  Third  nerve.  4.  Fourth 
5.  Optic  nerve.  6.  Sixth 
a.  Internal  carotid  artery. 


nerve. 
nerve. 
nerve. 
nerve, 


THE  BEEP  NERVES  OP  THE  ORBIT 

Mis    I  ROM  ABOVE   BY  REMOVING  THE 

BONE  AND  DIVIDING  THE  ELEVATOR 
OP  THE  UPPER  EYELID  AND  THE 
UPPER  RECTUS  MUSCLE. — a.  Inter- 
nal pterygoid  muscle,  b.  Temporal 
muscle.  r.  Cut  surface  of  bone. 
d.  Elevator  of  the  eyeli^l  and  upper 
rectug  muscle.  e.  Carotid  artery. 
1.  Optic  nerve.  2.  Fifth  nerve.  3. 
Ophthalmic  nerve.  4.  Third  nerve. 
5.  Sixth  nerve. 

The  inferior  branch  sends  a  branch  beneath  the  optic  nerve  to 
the  internal  rectus,  another  to  the  inferior  rectus,  and  a  long 
branch  to  the  inferior  oblique  muscle.     From  the  latter  a  short 
12 


134  THE   DISSECTOR. 

thick  branch  is  given  to  the  ophthalmic  ganglion,  forming  its 
inferior  root. 

The  FOURTH  NERVE  (patheticus,  trochlearis),  the  smallest  of 
the  cerebral  nerves,  pierces  the  dura  mater  below  the  third  nerve, 
and  passes  obliquely  upwards  to  enter  the  orbit  through  the 
upper  part  of  the  sphenoidal  fissure;  it  therefore  crosses  the 
third  nerve.  Entering  the  orbit,  the  nerve  passes  across  the 
levator  palpebrae  near  its  origin,  and  is  distributed  to  the  supe- 
rior oblique  or  trochlearis  muscle,  spreading  out,  contrary  to  the 
mode  of  distribution  of  the  other  nerves,  on  the  orbital  surface 
of  the  muscle. 

The  fourth  nerve  communicates  in  the  cavernous  sinus  with 
the  ophthalmic  nerve  and  the  carotid  plexus  of  the  sympathetic; 
it  also  sends  off  a  recurrent  filament,  which,  in  conjunction  with 
a  similar  offset  of  the  ophthalmic,  is  distributed  to  the  tentorium 
cerebelli.  Sometimes  the  communication  with  the  ophthalmic 
takes  place  in  the  orbit,  in  which  case  the  lachrymal  nerve  has 
the  appearance  of  arising  by  two  roots. 

The  OPHTHALMIC  NERVE,  the  upper  branch  of  the  Casserian 
ganglion,  passes  along  the  outer  wall  of  the  cavernous  sinus, 
below  the  fourth  nerve,  and  divides  into  three  branches,  frontal, 
lachrymal,  and  nasal.  The  nerve  communicates,  while  in  the 
sinus,  with  the  carotid  plexus  and  fourth  nerve,  and  sends  off  a 
recurrent  branch  to  the  tentorium  cerebelli. 

The  FRONTAL  NERVE  enters  the  orbit  immediately  to  the  outer 
side  of  the  fourth  nerve,  and  passing  forwards  for  some  distance 
upon  the  levator  palpebrae  muscle,  divides  into  a  supra-orbital 
and  supra-trochlear  branch. 

The  supra-orbital  branch,  which  is  the  proper  continuation  of 
the  nerve,  passes  out  of  the  orbit  through  the  supra-orbital  notch, 
and  mounts  upon  the  forehead,  supplying  the  integument,  mus- 
cles, and  pericranium  (p.  lit).  While  in  the  notch  it  sends 
filaments  to  the  upper  eyelid. 

The  supra-trochlear  branch  passes  inwards  to  the  angle  of  the 
orbit,  above  the  pulley  of  the  superior  oblique  muscle,  and  is  dis- 
tributed to  the  inner  angle  of  the  eye,  the  root  of  the  nose,  and 
middle  line  of  the  forehead  (p.  117).  It  communicates  with  the 
infra-trochlear  branch  of  the  nasal  nerve. 

The  LACHRYMAL  NERVE,  the  smallest  of  the  three  branches  of 
the  ophthalmic,  enters  the  orbit  on  the  outer  side  of  the  frontal, 
but  inclosed  in  a  separate  sheath  of  dura  mater;  and  passes  for- 
wards, above  the  upper  border  of  the  external  rectus  muscle,  to 
the  lachrymal  gland,  where  it  divides  into  two  branches,  superior 
and  inferior.  The  superior  branch  passes  over  the  gland  which 
it  supplies  on  the  upper  surface,  and  traversing  a  foramen  in  the 


NEEVES   OP   THE   ORBIT.  135 

malar  bone,  communicates  with  the  subcutaneous  mala?  and  facial 
nerve.  The  inferior  branch  supplies  the  under  surface  of  the 
gland,  and  supplies  the  upper  lid  and  outer  angle  of  the  eye. 

The  lachrymal  nerve  sometimes  receives  the  branch  of  the  fourth  nerve 
destined  for  the  ophthalmic,  and  appears  to  arise  by  two  roots. 

The  NASAL  NERVE  (naso-ciliaris)  enters  the  orbit  between  the 
two  heads  of  the  external  rectus  and  between  the  two  branches 
of  the  third  nerve.  It  crosses  the  optic  nerve  in  company  with 
the  ophthalmic  artery,  and  passing  over  the  internal  rectus,  enters 
the  anterior  ethmoidal  foramen,  by  which  it  is  conducted  to  the 
cribriform  plate  of  the  ethmoid  bone.  It  then  passes  through 
the  slit-like  opening  by  the  side  of  the  crista  galli,  and  descends 
into  the  nose,  where  it  divides  into  an  internal  and  an  external 
branch.  The  internal  branch  is  distributed  to  the  mucous  mem- 
brane ;  and  the  external  branch,  passing  outwards  between  the 
nasal  bone  and  cartilage,  supplies  the  integument  of  the  exterior 
of  the  nose  as  far  as  its  tip. 

The  branches  of  the  nasal  nerve  are  the  ganglionic,  ciliary,  and 
infra-trochlear. 

The  ganglionic  branch,  about  half  an  inch  in  length  and  of 
small  size,  enters  the  upper  angle  of  the  ophthalmic  ganglion, 
and  constitutes  its  superior  or  long  root. 

The  long  ciliary  branches  are  two  or  three  filaments  given  off 
from  the  nerve  as  it  crosses  the  optic  nerve.  They  pierce  the 
sclerotic  coat  near  the  short  ciliary  nerves,  and  passing  through 
the  globe  of  the  eye  between  the  sclerotic  and  choroid,  are  dis- 
tributed to  the  iris. 

The  infra-trochlear  branch  is  given  off  close  to  the  anterior 
ethmoidal  foramen.  It  passes  forwards  along  the  upper  border 
of  the  internal  rectus  to  the  inner  angle  of  the  eye,  where  it  com- 
municates with  the  supra-trochlear  nerve,  and  is  distributed  to 
the  lachrymal  sac  and  inner  angle  of  the  orbit. 

The  SIXTH  NERVE  (abducens  oculi)  pierces  the  dura  mater  on 
the  body  of  the  sphenoid  bone,  and  passes  along  the  inner  wall 
of  the  cavernous  sinus,  below  the  other  nerves,  and  resting  against 
the  internal  carotid  artery  to  the  sphenoidal  fissure.  It  enters 
the  sphenoidal  fissure  above  the  ophthalmic  vein,  and  passing 
between  the  two  heads  of  the  external  rectus,  is  distributed  to 
that  muscle. 

In  the  cavernous  sinus  the  sixth  nerve  receives  several  filaments 
from  the  carotid  plexus. 

The  four  nerves  just  described  are  situated,  previously  to  their  entry 
into  the  orbit,  in  the  cavernous  sinus ;  the  first  three,  namely,  third,  fourth, 
and  three  branches  of  the  fifth,  in  the  outer  wall  of  the  sinus,  each  nerve 
being  inclosed  in  a  separate  sheath  of  dura  mater;  the  remaining  nerve, 
the  sixth,  in  the  internal  wall  of  the  sinus,  that  is,  between  the  sinus  and 


136 


THE   DISSECTOR. 


the  internal  carotid  artery.  Another  relation  of  the  nerves  is  that  from 
above  downwards ;  at  their  entrance  into  the  sinus  they  are  placed  in  the 
order  of  their  numbers,  namely,  third,  fourth,  fifth,  sixth ;  but  at  the 
ethmoidal  fissure,  the  fourth,  frontal,  and  lachrymal  are  the  highest,  these 


Fig.  4], 


A  TRANSVERSE  SECTION  OP  THE  CAVERNOUS 
SINUS  OF  THE  RIGHT  SIDE. — The  dura  mater, 
splitting  to  inclose  the  vessels  and  nerves.  2. 
The  internal  carotid  artery.  3.  The  sixth 
nerve,  receiving  a  branch  from  the  sympathetic. 
4.  The  cavernous  sinus.  5.  The  third  nerve. 
6.  The  fourth  nerve.  7.  The  ophthalmic  di- 
vision of  the  fifth  nerve. 


three  entering  the  orbit  above  the  origin  of  the  levator  palpebrae ;  the 
others  lie  in  the  following  relative  position — upper  branch  of  the  third, 
nasal,  lower  branch  of  the  third  and  sixth.  The  three  latter  all  pass 
between  the  two  heads  of  the  external  rectus.  Below  the  sixth  nerve, 
at  the  sphenoidal  fissure,  is  the  ophthalmic  vein. 

The  OPHTHALMIC  GANGLION  (ciliary ;  lenticular)  is  a  small  quad- 
rangular and  flattened  body  of  a  reddish  color,  situated  between 
the  optic  nerve  and  external  rectus. 


Fig.  42. 


A  REPRESENTATION  or 

SOME      OF      THE      NERVES 

OF  THE  ORBIT,  ESPECI- 
ALLY TO  SHOW  THE  LEN- 
TICULAR GANGLION. — 1. 
Ganglion  of  the  fifth. 
2.  Ophthalmic  nerve.  3. 
Upper  maxillary.  4.  Low- 
er maxillary.  5.  Nasal 
branch,  giving  the  long 
root  to  the  lenticular  gan- 
glion. 6.  Third  nerve.  7. 
Inferior  oblique  branch  of 
the  third  connected  with 
the  ganglion  by  the  short 
root.  8.  Optic  nerve.  9. 
Sixth  nerve.  10.  Sympa- 
thetic on  the  carotid 
artery. 


Its  branches  of  communication  are  three  in  number  :  one,  the 
long  root,  which  proceeds  from  its  superior  angle  and  joins  the 
nasal  nerve ;  a  short  and  thick  branch,  the  short  root,  which 
proceeds  from  its  inferior  angle  and  joins  the  inferior  branch  of 
the  third  nerve  ;  and  a  slender  filament  from  the  carotid  plexus, 
the  sympathetic  root. 

Its  branches  of  distribution  are  the  short  ciliary  nerves  ;  they 
proceed  from  the  anterior  angles  of  the  ganglion  in  two  groups, 


VESSELS   OF  THE   ORBIT.  137 

the  upper  group  consisting  of  about  four  filaments,  and  the  lower 
of  five  or  six.  They  accompany  the  ciliary  arteries  hi  a  waving 
course,  and  divide  into  a  number  of  filaments  which  pierce  the 
sclerotic  around  the  optic  nerve,  and  supply  the  tunics  of  the 
eyeball. 

Vessels  of  the  Orbit. 

The  vessels  of  the  orbit  are  the  ophthalmic  artery  and  vein 
with  their  branches. 

The  OPHTHALMIC  ARTERY  arises  from  the  internal  carotid,  just 
as  the  latter  vessel  pierces  the  dura  mater,  and  enters  the  orbit 
through  the  optic  foramen  lying  externally  to  the  optic  nerve. 
It  then  crosses  the  optic  nerve  to  the  inner  wall  of  the  orbit,  and 
at  the  inner  angle  of  the  eye  divides  into  two  terminal  branches, 
frontal  and  nasal. 

The  branches  of  the  ophthalmic  artery,  ten  in  number,  may  be 
arranged  in  two  groups,  the  first  group  including  the  vessels  dis- 
tributed to  the  circumference  of  the  orbit ;  and  the  second,  those 
which  supply  the  eyeball  and  its  muscles. 

First  Group. 

Lachrymal,  Palpebral, 

Supra-orbital,  Frontal, 

Posterior  ethmoidal,  Nasal. 

Anterior  ethmoidal, 

Second  Group. 
Muscular — anterior  ciliary, 
Ciliary,  short  and  long, 
Centralis  retinae. 

The  lachrymal  is  the  first  branch  of  the  ophthalmic  artery, 
and  is  usually  given  off  immediately  before  that  artery  enters 
the  optic  foramen.  It  follows  the  course  of  the  lachrymal  nerve, 
above  the  upper  border  of  the  external  rectus  muscle,  and  is 
distributed  to  the  lachrymal  gland.  The  small  branches  which 
escape  from  the  gland  supply  the  conjunctiva  and  upper  eyelid. 
The  lachrymal  artery  gives  off  a  malar  branch,  which  passes 
through  the  malar  bone  into  the  temporal  fossa,  and  inosculates 
with  the  deep  temporal  arteries,  while  some  of  its  branches  be- 
come subcutaneous  on  the  cheek,  and  anastomose  with  the  trans- 
verse facial. 

The  supra-orbital  artery  follows  the  course  of  the  frontal^ 
nerve,  resting  on  the  levator  palpebrae  muscle ;  it  passes  through 
the  supra-orbital  foramen,  and  divides  into  a  superficial  and  deep 
branch,  which  are  distributed  to  the  muscles  and  integument  of 
the  forehead,  and  to  the  pericranium.  At  the  supra-orbital 
foramen  it  sends  a  branch  inwards  to  the  diploe. 

12* 


138  .          THE   DISSECTOR. 

The  ethmoidal  arteries,  posterior  and  anterior,  pass  through 
the  ethmoidal  foramina,  and  are  distributed  to  the  falx  cerebri 
and  to  the  ethmoidal  cells  and  nasal  fossae.  The  latter  accom- 
panies the  nasal  nerve,  and  sends  a  branch  to  the  frontal  sinus. 

The  palpebral  arteries,  superior  and  inferior,  are  given  off 
from  the  ophthalmic,  near  the  inner  angle  of  the  orbit ;  they 
encircle  the  eyelids,  forming  a  superior  and  an  inferior  arch  near 
the  borders  of  the  lids,  between  the  orbicularis  palpebrarum  and 
tarsal  cartilage.  At  the  outer  angle  of  the  eyelids,  the  superior 
palpebral  inosculates  with  the  orbital  branch  of  the  temporal 
artery.  The  inferior  palpebral  sends  a  branch  to  the  nasal  duct. 

The  frontal  artery,  one  of  the  terminal  branches  of  the 
ophthalmic,  emerges  from  the  orbit  at  its  inner  angle,  and 
ascends  along  the  middle  of  the  forehead.  It  is  distributed  to 
the  integument,  muscles,  and  pericranium. 

The  nasal  artery,  the  other  terminal  branch  of  the  ophthalmic, 
passes  out  of  the  orbit  above  the  tendo-oculi,  and  divides  into 
two  branches  ;  one  of  which  inosculates  with  the  angular  artery, 
while  the  other,  the  dorsalis  nasi,  runs  along  the  ridge  of  the 
nose,  and  is  distributed  to  the  integument  of  that  organ.  The 
nasal  artery  sends  a  small  branch  to  the  lachrymal  sac. 

The  muscular  branches,  usually  two  in  number,  superior  and 
inferior,  supply  the  muscles  of  the  orbit ;  and  upon  the  anterior 
aspect  of  the  globe  of  the  eye  give  off  the  anterior  ciliary  arte- 
ries, which  pierce  the  sclerotic  near  its  margin  of  connection 
with  the  cornea,  and  are  distributed  to  the  iris.  It  is  the  con- 
gestion of  these  vessels  that  gives  rise  to  the  vascular  zone  around 
the  cornea  in  iritis. 

The  ciliary  arteries  are  divisible  into  three  groups,  short,  long, 
and  anterior. 

The  short  ciliary  (posterior),  from  ten  to  fifteen  in  number, 
pierce  the  sclerotic  around  the  entrance  of  the  optic  nerve,  and 
supply  the  choroid  coat  and  ciliary  processes.  The  long  ciliary, 
two  in  number,  pierce  the  sclerotic  on  opposite  sides  of  the  globe 
of  the  eye,  and  pass  forwards  between  it  and  the  choroid  to  the 
iris.  They  form  an  arterial  circle  around  the  circumference  of 
the  iris  by  inosculating  with  each  other,  and  from  this  circle 
branches  are  given  off  which  ramify  in  the  substance  of  the  iris, 
and  form  a  second  circle  around  the  pupil.  The  anterior  ciliary 
are  branches  of  the  muscular  arteries;  they  terminate  in  the  great 
arterial  circle  of  the  iris. 

The  centralis  retinas  artery  pierces  the  optic  nerve  obliquely, 
and  passes  forwards  in  the  centre  of  its  cylinder  to  the  retina, 
where  it  divides  into  branches,  which  ramify  in  the  inner  layer  of 
that  membrane.  It  supplies  the  retina,  hyaloid  membrane,  and 
zonula  ciliaris  ;  and,  by  means  of  a  branch  sent  forwards  through 


ANATOMY   OF   THE   NECK.  139 

the  centre  of  the  vitreous  humor  in  a  tubular  sheath  of  the  hya- 
loid membrane,  the  capsule  of  the  lens. 

The  OPHTHALMIC  VEIN  commences  at  the  inner  angle  of  the 
eye,  where  it  communicates  with  the  angular  vein  and  takes  the 
course  of  the  ophthalmic  artery,  receiving  the  veins  correspond- 
ing with  its  branches.  It  quits  the  orbit  through  the  sphenoidal 
fissure,  after  passing  between  the  two  heads  of  the  external  rectus, 
and  opens  into  the  cavernous  sinus.  At  the  sphenoidal  fissure  it 
lies  beneath  the  sixth  nerve. 

LACHRYMAL  GLAND. — The  lachrymal  gland  is  situated  at  the 
upper  and  outer  angle  of  the  orbit,  and  consists  of  two  portions, 
orbital  and  palpebral.  The  orbital  portion,  about  three-quarters 
of  an  inch  in  length,  is  flattened  and  oval  in  shape,  and  occupies 
the  lachrymal  fossa  in  the  orbital  plate  of  the  frontal  bone.  It 
is  in  contact  superiorly  with  the  periosteum,  with  which  it  is 
closely  connected  by  its  upper  and  convex  surface;  by  its  inferior 
or  jconcave  surface  it  is  in  relation  with  the  globe  of  the  eye,  and 
the  superior  and  external  rectus  ;  and  by  its  anterior  border  with 
the  broad  tarsal  ligament.  By  the  posterior  border  it  receives 
its  vessels  and  nerves.  The  palpebral  portion,  smaller  than  the 
preceding,  is  situated  in  the  upper  eyelid,  extending  downwards 
to  the  superior  margin  of  the  tarsal  cartilage.  It  is  continuous 
with  the  orbital  portion  above,  and  is  inclosed  in  an  investment 
of  dense  fibrous  membrane.  The  secretion  of  the  lachrymal 
gland  is  conveyed  away  by  from  eight  to  twelve  small  ducts  which 
run  for  a  short  distance  beneath  the  conjunctiva,  and  open  upon 
its  surface  by  a  series  of  pores,  about  one-twentieth  of  an  inch 
apart,  situated  in  a  curved  line  a  little  above  the  upper  border 
of  the  tarsal  cartilage. 

For  the  anatomy  of  the  appendages  of  the  eye,  and  the  rest  of  the 
lachrymal  apparatus,  the  student  is  referred  to  Chap.  V. 

ANATOMY  OP  THE  NECK. 

The  neck,  as  before  stated,  is  the  medium  of  communication 
and  connection,  between  the  head  and  the  trunk  of  the  body. 

Connection  is  established  by  means  of  the  integument  and 
sterno-mastoid  muscle,  the  muscles  of  the  prevertebral  region, 
vertebral  column,  and  muscles  of  the  back. 

Communication  is  effected  by  means  of  apparatuses  connected 
with  respiration  and  deglutition.  Associated  with  respiration  is 
the  larynx,' and  with  deglutition  the  os  hyoides,  the  tongue,  the 
soft  palate,  and  the  pharynx.  These  may  be  considered  as  the 
elements  of  the  neck,  and  form  so  many  regions,  by  which  the 
muscles  may  be  grouped  and  arranged. 


140 


THE   DISSECTOR. 


Thus  we  find  the — 

1.  Superficial  group. 

2.  Depressors  of  the  os  hyoides  and  larynx. 

3.  Elevators  of  the  os  hyoides  and  larynx. 

4.  Lingual  group. 

5.  Soft  palate  group. 

6.  Pharyngeal  group. 

7.  Pre vertebral  group. 

8.  Proper  muscles  of  the  larynx. 

These  eight  groups,  therefore,  will  form  so  many  distinct 
ideas,  by  which  the  composition  of  the  neck  and  the  arrangement 
of  its  muscles  may  be  associated  in  the  mind.  To  facilitate  still 
more  the  learning  of  these  muscles,  the  student  is  informed  that, 
with  the  exception  of  the  first  two,  each  group  consists  of  five 
muscles.  This  is  better  shown  in  the  following  table : — 


1.  Superficial  group. 
Platysma  myoides, 
Sterno-cleido-mastoideus. 

2.  Depressors  of  the 

os  hyoides  and  larynx. 

Sterno-hyoideus, 
Sterno-thyroideus, 
Thyro-hyoideus, 
Omo-hyoideus. 

3.  Elevators  of  the 

os  hyoides  and  larynx. 
Digastricus, 
Stylo-hyoideus, 
Mylo-hyoideus, 
Genio-hyoideus, 
Genio-hyo-glossus. 

4.  Muscles  of  the  tongue. 
Genio-hyo-glossus, 
Hyo-glossus, 
Lingualis, 
Stylo-glossus, 
Palato-glossus. 

5.  Muscles  of  the  soft  palate. 
Levator  palati, 


Tensor  palati, 
Azygos  uvula?, 
Palato-glossus, 
Palato-pharyngeus. 

6.  Muscles  of  the  pharynx. 

Constrictor  inferior, 
Constrictor  medius, 
Constrictor  superior, 
Stylo-pharyngeus, 
Palato-pharyngeus. 

7.  Prevertebral  group. 

Rectus  anticus  major, 
Kectus  anticus  minor, 
Scalenus  anticus, 
Scalenus  posticus, 
Longus  colli. 

8.  Muscles  of  the  larynx. 


Crico-thyroid, 
Crico-arytaenoid,  posticus, 
Crico-aryta3noid,  lateralis, 
Thyro-aryta3noid, 
Arytaenoid. 

After  this  arrangement  of  the  muscles  has  been  well  considered, 
and,  we  may  add,  learnt  by  heart,  the  student  should  commence 
the  dissection  of  one  side  of  the  neck  with  a  view  to  see  their 
connections  and  relations.  With  this  object  an  incision  should 


DEEP  CERVICAL  FASCIA.  141 

be  made  along  the  middle  line  of  the  neck  from  the  chin  to  the 
sternum,  and  bounded  superiorly  and  inferiorly  by  two  trans- 
verse incisions;  the  superior  one  carried  along  the  margin  of  the 
lower  jaw,  and  across  the  mastoid  process  to  the  tubercle  on  the 
occipital  bone,  the  inferior  one  along  the  clavicle  to  the  acromion 
process.  The  square  flap  of  integument  thus  included  should  be 
turned  back  from  the  entire  side  of  the  neck,  which  brings  into 
view  the  superficial  fascia. 

The  superficial  fascia  consists  of  two  layers,  between  which  is 
placed  the  platysma  myoides  muscle.  The  external  layer  must 
therefore  be  reflected  from  off  its  fibres,  to  the  same  extent  with 
the  flap  of  integument,  observing  to  dissect  always  in  the  course 
of  the  fibres. 

The  PLATYSMA  MYOIDES  (rfa.aT'vf,  fiv<,  fZSof,  broad  muscle-like 
lamella)  is  a  thin  plane  of  muscular  fibres,  situated  between  the 
two  layers  of  the  superficial  cervical  fascia;  it  arises  from  the 
superficial  fascia  over  the  pectoralis  major  and  deltoid  muscles, 
and  passes  obliquely  upwards  and  inwards  along  the  side  of  the 
neck  to  be  inserted  into  the  side  of  the  chin,  oblique  line  of  the 
lower  jaw,  the  angle  of  the  mouth,  and  into  the  cellular  tissue  of 
the  face.  The  most  anterior  fibres  are  continuous  beneath  the 
chin  with  the  muscle  of  the  opposite  side;  the  next  interlace  with 
the  depressor  anguli  oris  and  depressor  labii  inferioris ;  and  the 
most  posterior  fibres  are  disposed  in  a  transverse  direction  across 
the  side  of  the  face,  arising  from  the  fibrous  covering  of  the 
parotid  gland,  and  inserted  into  the  angle  of  the  mouth,  consti- 
tuting the  risorius  Santorini1  (page  122).  The  entire  muscle  is 
analogous  to  the  cutaneous  muscle  of  brutes,  the  panniculus  car- 
nosus. 

Upon  removing  the  platysma  and  with  it  the  deep  layer  of  superficial 
fascia,  we  bring  into  view  the  external  jugular  vein,  and  ascending 
branches  of  the  cervical  plexus  of  nerves.  The  jugular  vein  is  lying 
obliquely  along  the  neck,  parallel  with  the  fibres  of  the  platysma  my- 
oides, while  it  crosses  the  direction  of  the  sterno-mastoid  muscle. 

The  sterno-mastoid  is  as  yet  concealed  from  view  by  a  layer  of  fascia, 
which  covers  in  the  whole  of  the  side  of  the  neck.  This  is  the  deep  cer- 
vical fascia,  the  reflections  of  which  we  have  next  to  examine. 

The  deep  cervical  fascia  is  a  strong  cellulo-fibrous  membrane, 
which  invests  the  neck,  forming  sheaths  for  the  various  muscles, 
and  retaining  and  supporting  the  vessels  and  nerves.  It  is  at- 
tached posteriorly  along  the  middle  line  to  the  ligamentum 
nuchae,  being  overlapped  by  the  trapezius  muscle;  passes  for- 
wards to  the  posterior  border  of  the  sterno-mastoid,  and  divides 

1  John  Dominico  Santorinus,  Professor  of  Anatomy  in  Venice.  His 
notice  of  this  muscle  is  contained  in  his  "Observations  Anatomicse," 
published  in  1724. 


142  THE   DISSECTOR. 

into  two  layers  which  embrace  that  muscle,  and  unite  again  at 
its  anterior  border.  It  is  then  directed  onwards  to  the  middle 
line,  where  it  becomes  continuous  with  the  deep  fascia  of  the 
opposite  side  of  the  neck.  The  anterior  layer,  that  which  is  su- 
perficial to  the  sterno-mastoid,  is  prolonged  upwards  on  the  side 
of  the  jaw  and  parotid  gland,  to  the  zygoma,  and  downwards 
over  the  clavicle  and  pectoralis  major  muscle.  The  posterior 
layer,  which  can  only  be  examined  by  removing  or  drawing  aside 
the  sterno-mastoid  muscle,  is  attached  superiorly  to  the  styloid 
process  of  the  temporal  bone,  and  is  thence  reflected  to  the  angle 
of  the  jaw,  forming  the  stylo-maxillary  ligament.  Inferiorly  it 
forms  a  loop,  which  acts  as  a  pulley  to  the  omo-hyoid  muscle, 
and  is  then  continued  downwards  behind  the  clavicle,  so  as  to 
inclose  the  subclavius  muscle.  The  extremities  of  the  latter 
portion  are  attached  firmly  to  the  cartilage  of  the  first  rib  and 
coracoid  process :  hence  it  is  named  costo-coracoid  membrane  or 
ligament.  In  the  middle  line  the  deep  fascia  is  connected  with 
the  sternum. 

This  fascia  is  of  great  importance  in  a  surgical  point  of  view.  In  its 
normal  condition  it  binds  down  firmly  all  the  structures  of  the  neck, 
and  preserves  their  natural  position.  When,  however,  tumors  form 
beneath  it,  as  bronchocele,  enlargements  of  the  lymphatic  glands,  aneu- 
rism, &c.,  the  pressure  which  it  then  exerts  may  be  fatal  to  the  patient, 
from  compression  of  the  trachea,  larynx,  and  nerves,  unless  the  tension 
be  relieved  by  incision. 

If  the  deep  fascia  be  divided  in  the  direction  of  the  sterno-mastoid 
muscle,  and  turned  aside,  that  muscle  will  be  brought  into  view,  and  the 
posterior  part  of  its  sheath  examined. 

The  STERNO-CLETDO-MASTOIDEUS  is  the  large  oblique  muscle  of 
the  neck.  It  arises,  as  implied  by  its  name,  from  the  sternum 
and  clavicle  (xXsiStoi/),  and  passes  obliquely  upwards  and  back- 
wards to  be  inserted  into  the  mastoid  process  of  the  temporal, 
and  into  the  superior  curved  line  of  the  occipital  bone.  The 
sternal  portion  arises  by  a  rounded  tendon,  increases  in  breadth 
as  it  ascends,  and  spreads  out  to  a  considerable  extent  at  its 
insertion.  The  clavicular  portion  is  broad  and  fleshy,  and  sepa- 
rate from  the  sternal  portion  below,  but  becomes  gradually 
blended  with  the  posterior  surface  of  the  latter  as  it  ascends. 

ACTIONS. — The  platysma  produces  a  muscular  traction  on  the  integu- 
ment of  the  neck,  which  prevents  it  from  falling  so  flaccid  in  old  persons 
as  it  would  if  the  extension  of  the  skin  were  the  mere  result  of  elasticity. 
It  draws  also  upon  the  angle  of  the  mouth,  and  is  one  of  the  depressors 
of  the  lower  jaw.  The  sterno-mastoid  muscles  are  the  great  anterior 
muscles  of  connection  between  the  thorax  and  the  head.  Both  muscles 
acting  together  bow  the  head  directly  forwards.  The  clavicular  portions, 
acting  more  forcibly  than  the  sternal,  give  stability  and  steadiness  to  the 
head  in  supporting  great  weights.  Either  muscle  acting  singly  would 
draw  the  head  towards  the  shoulder  of  the  same  side,  and  carry  the  face 
towards  the  opposite  side. 


POSTERIOR   TRIANGLE.  143 

The  sterno-mastoid  muscle,  stretching  obliquely  across  the 
side  of  the  neck,  divides  the  latter  into  two  great  triangles,  an- 
terior and  posterior;  each  of  which  is  subdivided  into  smaller 
triangles.  The  great  anterior  triangle,  having  its  base  at  the 

Fig.  43. 


THE  MUSCLES  OF  THE  ANTERIOR  ASPECT  OP  THE  NECK;  ON  THE  LEFT 
SIDE  THE  SUPERFICIAL  MUSCLES  ARE  SEEN,  AND  ON  THE  RIGHT  THE  DEEP. 
— 1.  The  posterior  belly  of  the  digastricus  muscle.  2.  Its  anterior  belly.  The 
aponeurotic  pulley  through  which  its  tendon  is  seen  passing,  is  attached  to  the 
body  of  the  os  hyoides,  3.  4.  The  stylo-hyoideus  muscle,  transfixed  by  the 
posterior  belly  of  the  digastricus.  5.  The  mylo-hyoideus.  6.  The  genio- 
hyoideus.  7.  The  tongue.  8.  The  hyo-glossus.  9.  The  stylo -glossus.  10. 
The  stylo -pharyngeus.  11.  The  sterno-mastoid  muscle.  12.  Its  sternal  origin. 
13.  Its  clavicular  origin.  14.  The  sterno-hyoid.  15.  The  sterno-thyroid  of  the 
right  side.  16.  The  thyro-hyoid.  17.  The  hyoid  portion  of  the  omo-hyoid. 
18,  18.  Its  scapular  portion;  on  the  left  side,  the  tendon  of  the  muscle  is  seen 
to  be  bound  down  by  a  portion  of  the  deep  cervical  fascia.  19.  The  clavicular 
portion  of  the  trapezius.  20.  The  scalenus  anticus,  of  the  right  side.  21.  The 
scalenus  posticus.  22.  The  scalenus  medius. 

lower  jaw  and  apex  at  the  sternum,  is  bounded  in  front  by  the 
mid-line  of  the  neck,  behind  by  the  sterno-mastoid,  and  above 
by  the  body  of  the  lower  jaw.  This  triangular  space  contains 
the  carotid  arteries,  internal  jugular  vein,  and  large  nerves  of  the 
neck ;  the  anterior  border  of  the  sterno-mastoid  being  the  guide 
for  the  incision  in  ligature  of  the  common  carotid  artery. 

The  posterior  triangle',  having  its  base  at  the  clavicle  and  apex 
at  the  occiput,  is  bounded  in  front  by  the  sterno-mastoid  muscle; 
behind  by  the  trapezius,  and  below  by  the  clavicle ;  it  contains 


144  THE   DISSECTOR. 

in  its  lower  part  the  subclavian  artery  and  vein,  with  some  of 
their  branches,  and  the  brachial  plexus  of  nerves.  Both  trian- 
gular spaces  are  covered  in  by  the  deep  cervical  fascia  and  pla- 
tysraa  myoides  muscle  ;  and  the  external  jugular  vein,  in  its  ver- 
tical course  down  the  neck,  passes  from  the  anterior  triangle 
across  the  sterno-mastoid  muscle  to  the  posterior  triangle. 

Fig.  44. 


THE  TRIANGLES  OP  THE  NECK,  WITH  THE  EXTERNAL  JUGULAR  VEIN  AND 
ASCENDING  BRANCHES  OP  THE  CERVICAL  PLEXUS. — 1.  The  sterno-mastoid 
muscle,  which  divides  the  side  of  the  neck  into  two  great  triangles,  the  anterior 
and  posterior,  a.  The  submaxillary  triangle,  b.  The  superior  carotid  triangle. 
c.  The  inferior  carotid  triangle,  d.  The  sub-occipital  triangle,  e.  The  sub- 
clavian triangle.  2.  The  border  of  the  lower  jaw.  3.3.  The  digastric  muscle. 
4.  The  superior  belly  of  the  omo-hyoid  muscle.  5.  Its  inferior  belly.  6.  The 
trapezius  muscle.  7.  The  parotid  gland.  8.  The  external  jugular  vein.  9.  A 
dotted  line,  marking  the  direction  of  the  fibres  of  the  platysma  myoides  muscle. 
10.  A  small  arrow,  showing  the  direction  of  the  incision  for  opening  the  jugular 
vein.  11.  The  superficial  colli  nerve,  which  forms  a  plexus  with  (12)  a  branch 
from  the  facial  nerve,  over  the  submaxillary  triangle.  13.  The  auricularis 
magnus  nerve.  14.  The  occipitalis  minor.  15.  The  descending  superficial 
branches  of  the  plexus.  16.  The  spinal  accessory  nerve. 

The  sterno-mastoid  may  now  be  removed  by  dividing  it  through  the 
middle  and  turning  aside  its  ends.  The  upper  end  will  be  found  to  be 
perforated  by  a  large  nerve,  the  spinal  accessory  of  the  eighth  pair,  which, 
after  supplying  the  sterno-mastoid,  takes  its  course  across  the  posterior 
triangle  to  the  under  part  of  the  trapezius.  The  deep  layer  of  fascia  is 
then  to  be  dissected  from  off  the  side  of  the  larynx  and  trachea  towards 
the  mid-line,  when  the  second  group  of  muscles,  the  depressors  of  the  os 
hyoides  and  larynx,  will  be  brought  into  view. 

Second  Group. — Depressors  of  the  os  hyoides  and  larynx. 
Sterno-hyoid,  Thyro-hyoid, 

Sterno-thyroid,  Omo-hyoid. 


OMO-HYOIDEUS.  145 

The  STERNO-HYOIDEUS  is  a  narrow,  ribbon-like  muscle,  arising 
from  the  posterior  surface  of  the  first  bone  of  the  sternum,  and 
from  the  posterior  sterno-clavicular  ligament  (sometimes  from  the 
inner  extremity  of  the  clavicle,  and  sometimes  from  the  cartilage 
of  the  first  rib).  It  is  inserted  into  the  lower  border  of  the  os 
hyoides.  The  sterno-hyoidei  are  separated  by  a  considerable 
interval  at  the  root  of  the  neck,  but  approach  each  other  as  they 
ascend  ;  they  are  frequently  traversed  below  by  a  tendinous  inter- 
section. 

The  sterno-hyoideus  may  be  divided  through  the  middle,  and  its  ends 
turned  aside. 

The  STERNO-THYROIDEUS,  broader  than  the  preceding,  beneath 
which  it  lies,  arises  from  the  posterior  surface  of  the  upper  bone 
of  the  sternum,  and  from  the  cartilage  of  the  first  rib  ;  it  is  inserted 
into  the  oblique  line  on  the  great  ala  of  the  thyroid  cartilage.  The 
inner  borders  lie  in  contact  along  the  middle  line,  and  the  muscles 
are  marked  by  a  tendinous  intersection  at  their  lower  part. 

The  THYRO-HYOIDEUS  is  the  continuation  upwards  of  the  sterno- 
thyroid  muscle.  It  arises  from  the  oblique  line  on  the  thyroid 
cartilage,  and  is  inserted  into  the  lower  border  of  the  body,  and 
into  the  great  cornu  of  the  os  hyoides  for  one-half  its  length. 

The  OMO-HYOIDEUS  (<>o$,  shoulder)  is  a  double-bellied  muscle 
passing  obliquely  across  the  neck  from  the  scapula  to  the  os  hy- 
oides ;  it  forms  an  obtuse  angle  behind  the  sterno-mastoid  muscle, 
and  is  retained  in  that  position  by  means  of  a  process  of  the  deep 
cervical  fascia  which  is  connected  to  the  inner  border  of  its  ten- 
don. It  arises  from  the  upper  border  of  the  scapula,  and  from 
the  transverse  ligament  of  the  supra-scapular  notch,  and  is  inserted 
into  the  os  hyoides  at  the  junction  of  the  body  and  great  cornu. 

ACTIONS. — The  four  muscles  of  this  group  are  depressors  of  the  os  hy- 
oides and  larynx.  The  three  former  drawing  these  parts  downwards  in 
tin-  middle  line,  and  the  two  omo-hyoidei  regulating  their  traction  to  the 
one  or  other  side  of  the  neck,  according  to  the  position  of  the  head.  The 
orno-hyoid  muscles,  by  means  of  their  connection  with  the  cervical  fascia, 
are  rendered  tensors  of  that  portion  of  the  deep  cervical  fascia  which 
covers  the  lower  part  of  the  neck,  between  the  two  sterno-mastoid  muscles. 

The  omo-hyoid  muscle,  crossing  the  neck  obliquely  in  a  direc- 
tion opposite  to  that  of  the  sterno-mastoid,  and  crossing  also  the 
anterior  and  posterior  triangular  spaces,  subdivides  the  latter 
into  smaller  triangles.  The  inferior  angle  of  the  great  anterior 
triangle,  cut  off  by  the  upper  belly  of  the  omo-hyoideus,  is  the 
inferior  carotid  triangle,  while  the  space  above  is  the  superior 
carotid  triangle.  The  apicial  portion  of  the  great  posterior  tri- 
angular space  is  the  occipital  triangle;  while  the  space  between 
the  omo-hyoid  and  the  clavicle  is  the  subclavian  triangle.  The 
latter  contains  the  subclavian  artery  and  vein,  and  brachial 
13 


146  THE   DISSECTOR. 

plexus  of  nerves ;  and  is  bounded  in  front  by  the  sterno-mastoid, 
above  by  the  orao-hyoid,  and  below  by  the  clavicle.  The  exter- 
nal jugular  vein  enters  this  space  to  join  the  subclavian  vein, 
and  it  is  here  that  the  operation  of  tying  the  subclavian  artery 
is  performed. 

If  the  sterno-hyoid  and  sterno-thyroid  muscles  be  divided,  and  the 
ends  turned  aside,  the  thyroid  gland  will  be  brought  into  view,  lying 
upon  the  trachea,  the  two  lobes  being  connected  by  a  transverse  portion 
which  crosses  the  air-tube. 

THYROID  GLAND. — The  thyroid  gland  consists  of  two  lobes, 
which  are  placed  one  on  each  side  of  the  trachea,  and  are  connected 
with  each  other  by  means  of  an  isthmus,  which  crosses  its  upper 
rings,  usually  the  third  and  fourth ;  but  in  this  respect  there  is 
some  variety,  a  point  necessary  to  be  remembered  in  operations 
on  the  trachea.  The  lobes  are  somewhat  conical  in  shape,  being 
larger  below  than  above,  and  the  smaller  end  is  continued 
upwards  to  the  side  of  the  thyroid  cartilage.  The  isthmus  is 
connected  with  the  lower  third  of  the  two  lobes,  and  often  gives 
origin  to  a  process  of  variable  length  and  size,  called  the  pyramid 
or  third  lobe.  The  pyramid  is  generally  situated  on  the  left  side 
of  the  isthmus,  and  is  sometimes  derived  from  the  left  lobe.  The 
left  lobe  is  somewhat  smaller  than  the  right,  the  weight  of  the 
entire  gland  being  about  one  ounce  and  a  half.  It  is,  however, 
larger  in  young  persons  and  females  than  in  adult  males,  and  under- 
goes a  slight  increase  during  menstruation.  Its  permanent  en- 
largement constitutes  bronchocele,  goitre,  or  the  Derbyshire  neck. 

The  structure  of  the  thyroid  is  of  a  brownish-red  color,  and  is  com- 
posed of  a  dense  aggregation  of  minute  and  independent  membranous 
cavities  inclosed  by  a  plexus  of  capillary  vessels,  and  connected  together 
by  cellular  tissue.  The  cavities  are  filled  with  a  yellowish  fluid,  in 
which  are  found  cytoblasts  and  cells ;  the  latter  measuring  y^g  of  an 
inch  in  diameter.  In  young  animals  the  cytoblasts  lie  in  contact  with 
the  internal  wall  of  the  cavities,  and  constitute  a  kind  of  tessellated 
epithelium. 

A  muscle  is  occasionally  found  connected  with  its  isthmus,  or 
with  the  pyramid,  and  is  attached,  superiorly,  to  the  body  of  the 
os  hyoides,  or  to  the  thyroid  cartilage.  It  was  named  by  Soem- 
mering  the  "  levator  glandulce  thyroidece." 

Vessels  and  Nerves. — It  is  abundantly  supplied  with  blood  by 
the  superior  and  inferior  thyroid  arteries.  Sometimes  an  addi- 
tional artery  is  derived  from  the  arteria  innominata,  and  ascends 
upon  the  front  of  the  trachea  to  be  distributed  to  the  gland. 
The  wounding  of  the  latter  vessel,  in  tracheotomy,  might  be  fatal 
to  the  patient.  The  nerves  are  derived  from  the  superior  laryn- 
geal,  and  from  the  middle  and  inferior  cervical  ganglia  of  the 
sympathetic. 

The  TRACHEA  may  now  be  examined  with  reference  to  the  ope- 
ration of  tracheotomy. 


MUSCLES   OF   THE   OS   HYOIDES.  147 

Operation. — Next  to  bleeding,  tracheotomy  is  one  of  the  most  important 
operations  on  the  human  body,  from  the  emergency  of  the  circumstances 
under  which  the  surgeon  is  called  upon  to  act,  and  from  the  liability  of 
their  occurrence  to  every  practitioner  and  at  any  moment.  The  student 
should  not  omit  to  perform  this  operation  while  dissecting  the  neck,  for, 
although  trifling  in  itself,  it  might  be  the  instant  means  of  saving,  if  not 
of  restoring  life.  If  called  unexpectedly  to  a  patient  laboring  under 
symptoms  of  threatened  suffocation,  he  would  not  hesitate  to  perform  it 
with  his  penknife ;  therefore  he  taust  familiarize  himself  with  its  steps. 

An  incision  is  to  be  made  to  the  extent  of  an  inch  and  a  half  along  the 
middle  line  of  the  neck,  just  above  the  sternum.  This  may  divide  the 
integument  and  superficial  fascia.  The  next  incision  takes  him  to  the 
space  between  the  two  sterno-thyroid  muscles  ;  these  are  to  be  separated, 
an  opening  made  into  the  trachea,  and  a  canula,  or  writing  quill,  in- 
serted into  it.  This  is  the  only  part  of  the  operation  that  requires  care  ; 
for  some  large  veins,  the  inferior  thyroid,  and  occasionally  an  inferior 
thyroid  artery  from  the  innominata,  lie  immediately  upon  the  trachea. 
The  bleeding  resulting  from  the  wound  of  any  of  these  vessels  might  be 
fatal  from  pouring  into  the  trachea.  In  the  case  of  the  artery  it  would 
be  necessary  to  tie  the  divided  extremities. 

LARYNGOTOMY  is  practised  a  little  higher  in  the  neck,  immediately 
below  the  thyroid  cartilage.  The  structures  are  to  be  divided  as  in  the 
previous  operation,  and  the  point  of  a  bistoury  introduced  into  the  larynx 
through  the  crico-thyroid  membrane,  in  the  space  left  by  the  divergence 
of  the  two  crico-thyroid  muscles.  A  small  branch  of  communication 
between  the  two  superior  thyroid  arteries  (inferior  laryngeal)  crosses  this 
ligament,  the  division  of  which,  as  it  might  give  rise  to  disagreeable 
hemorrhage,  must  be  carefully  avoided. 

Third  Group. — Elevators  of  the  os  hyoides. 

Digastricns, 
Stylo-hyoid, 
Mylo-hyoid. 
Genio-hyoid. 
Genio-hyo-glossus. 

To  dissect  these  muscles  the  neck  should  be  supported  by  a  high 
block,  and  the  head  thrown  backwards.  The  deep  fascia  should  be 
carefully  removed,  together  with  any  cellular  tissue  or  fat  which  may 
impede  the  view. 

The  DIGASTRICUS  (8tj,  twice,  yavtw,  belly)  is  a  small  muscle 
situated  immediately  beneath  the  side  of  the  body  of  the  lower 
jaw  ;  it  is  fleshy  at  each  extremity,  and  tendinous  in  the  middle. 
It  arises  from  the  digastric  fossa  and  anterior  border  of  the 
mastoid  process  of  the  temporal  bone,  and  is  inserted  into  a  de- 
pression on  the  inner  side  of  the  lower  jaw,  close  to  the  sym- 
physis.  The  middle  tendon  is  held  in  connection  with  the  body 
of  the  os  hyoides  by  an  aponeurotic  loop,  through  which  it  plays 
as  through  a  pulley;  the  loop  being  lubricated  by  a  synovial 
membrane.  A  thin  layer  of  aponeurosis  is  given  off  from  the 
tendon  of  the  digastricus  at  each  side,  which  is  connected  with 


148  THE   DISSECTOR. 

the  body  of  the  os  hyoides,  and  forms  a  strong  plane  of  fascia 
between  the  anterior  portions  of  the  two  muscles.  This  fascia 
is  named  the  supra-hyoidean. 

The  digastricus  muscle  incloses  on  two  sides,  the  lower  jaw 
being  the  third,  a  small  triangular  space  which  is  named,  from 
its  situation,  submaxillary  triangle;  while  it  constitutes  the  upper 
boundary  of  the  superior  carotid  triangle,  the  other  two  sides  of 
the  latter  being  the  omo-hyoid  below,  and  the  sterno-mastoid 
behind.  The  student  has  now  before  him  the  three  subdivisions 
of  the  anterior  triangular  space  of  the  neck,  namely,  submaxillary , 
superior  carotid,  and  inferior  carotid. 

In  the  submaxillary  triangle  he  will  find  the  submaxillary 
gland,  facial  artery,  and  submental  artery,  the  floor  of  the  trian- 
gular space  being  formed  by  the  mylo-hyoideus  muscle. 

In  the  superior  carotid  triangle  is  the  common  carotid  artery, 
dividing  into  the  external  and  internal  carotid,  the  internal  jugu- 
lar vein,  the  hypoglossal  nerve,  descendens  noni,  pneumogastric, 
and  behind  the  sheath  of  the  carotid  vessels,  the  sympathetic 
nerve. 

In  the  inferior  carotid  triangle  is  the  sheath  of  the  common 
carotid  artery,  the  internal  jugular  vein  and  pneumogastric 
nerve  being  inclosed  in  the  sheath  with  the  artery. 

SUBMAXILLARY  GLAND. — This  salivary  gland,  situated  in  the 
submaxillary  triangle,  is  of  a  rounded  form.  It  rests  on  the 
mylo-hyoideus,  hyo-glossus,  and  stylo-glossus  muscles,  and  is 
separated  from  the  parotid  gland  by  the  stylo-maxillary  ligament. 
Its  lateral  boundaries  are  the  lower  jaw,  against  which  it  lies, 
and  the  digastricus  muscle,  and  it  is  covered  in  by  the  deep  cer- 
vical fascia  and  platysma.  Its  excretory  duct  (Wharton's), 
about  two  inches  in  length,  issues  from  the  middle  of  the  gland 
and  passes  between  the  mylo-hyoideus  and  hyo-glossus  to  the 
fraanum  linguaa,  by  the  side  of  which  it  terminates  at  the  apex  of 
a  papilla.  A  process  of  the  gland  is  prolonged  with  the  duct 
for  a  short  distance  behind  the  mylo-hyoideus. 

The  structure  of  the  submaxillary  gland  is  similar  to  that  of 
the  parotid  already  described  (page  122),  but  its  lobes  are  larger 
and  less  firmly  held  together  by  cellular  tissue.  Its  duct  also  is 
thinner,  being  composed  only  of  a  fibrous  coat  lined  by  mucous 
membrane. 

The  submaxillary  gland  has  lying  in  a  groove  upon  its  upper 
surface  the  facial  artery. 

The  STYLO-HYOIDEUS  is  a  small  and  slender  muscle,  situated  in 
immediate  relation  with  the  posterior  belly  of  the  digastricus 
muscle,  by  which  it  is  pierced.  It  arises  from  the  middle  of  the 
styloid  process,  and  is  inserted  into  the  body  of  the  os  hyoides 
near  the  middle  line. 


SUBLINQUAL   GLAND.  149 

The  digastricus  must  be  divided  at  its  insertion  into  the  lower  jaw,  its 
attachment  to  the  os  hyoides  with  that  of  the  stylo-hyoideus  separated, 
and  the  muscles  turned  aside  in  order  to  bring  the  next  muscle  into 
view.  The  supra-hyoidean  fascia,  and  any  cellular  tissue  and  fat  which 
may  disfigure  the  muscle,  should  also  be  dissected  away. 

The  MYLO-HYOIDEUS  (/AVX^,  mola,  i.  e.t  attached  to  the  molar 
ridge  of  the  lower  jaw)  is  a  broad  and  triangular  plane  of  mus- 
cular fibres,  forming,  with  its  fellow  of  the  opposite  side,  the 
inferior  wall  or  floor  of  the  mouth.  It  arises  from  the  molar 
ridge  of  the  lower  jaw,  and  proceeds  obliquely  inwards  to  be 
inserted  into  the  raphe  of  the  two  muscles  and  body  of  the  os 
hyoides  ;  the  raphe  is  sometimes  deficient  at  its  anterior  part. 

After  the  mylo-hyoides  has  been  examined,  it  should  be  cut  away 
from  its  origin  and  insertion,  and  completely  removed.  The  view  of  the 
next  muscles  would  also  be  greatly  improved  by  dividing  the  lower  jaw 
a  little  to  the  side  of  the  symphysis,  and  drawing  it  outwards  or  removing 
it  altogether,  if  the  ramus  have  been  already  cut  across  in  dissecting  the 
internal  pterygoid  muscle.  The  tongue  may  then  be  drawn  out  of  the 
mouth  by  means  of  a  hook. 

The  GENIO-HYOIDEUS  (ytvtt.ov,  the  chin)  arises  from  a  small 
tubercle  on  the  inner  side  of  the  symphysis  of  the  lower  jaw,  and 
is  inserted  into  the  body  of  the  os  hyoides.  It  is  a  short  and 
slender  muscle,  very  closely  connected  with  its  fellow  and  with 
the  border  of  the  following. 

The  GENIO-HYO-GLOSSUS  (yXwooa,  the  tongue)  is  a  triangular 
muscle,  narrow  and  pointed  at  its  origin  from  the  lower  jaw, 
broad  and  fun-shaped  at  its  attachment  to  the  tongue.  It  arises 
from  a  tubercle  immediately  above  that  of  the  genio-hyoideus, 
and  spreads  out  to  be  inserted  into  the  whole  length  of  the 
tongue,  from  its  base  to  the  apex,  and  into  the  os  hyoides. 

The  whole  of  this  group  of  muscles  acts  upon  the  os  hyoides  when  the 
lower  jaw  is  closed,  and  upon  the  lower  jaw  when  the  os  hyoides  is 
drawn  downwards  and  fixed  by  the  depressors  of  the  os  hyoides  and 
larynx.  The  genio-hyo-glossus  is  moreover  a  muscle  of  the  tongue. 

The  removal  of  the  mylo-hyoideus  brings  into  view,  besides  the  last 
two  muscles,  the  duct  of  the  submaxillary  gland,  and  the  third  and 
smallest  of  the  salivary  glands,  the  sublingual. 

SUBLINGUAL  GLAND.— The  sublingual  is  a  long  and  flattened 
gland  situated  in  the  floor  of  the  mouth  by  the  side  of  the  fra- 
num  linguae  and  tongue,  and  covered  on  this  aspect  by  the  mu- 
cous membrane.  At  the  fraenum  it  is  in  relation  with  its  fellow 
of  the  opposite  side,  and  in  the  rest  of  its  course  lies  between  the 
lower  jaw  and  genio-hyo-glossus,  being  bounded  below  by  the 
mylo-hyoideus.  It  is  in  relation  also  with  tfce  duct  of  the  sub- 
maxillary  gland  and  the  hypoglossal  nerve. 

The  sublingual  gland  in  essential  structure  is.  similar  to  the 
other  saliyary  glands  j  but  the  lobules,  are  more  loosejv  connected, 


150 


THE   DISSECTOR. 


and  in  some  instances  lie  apart  from  each  other.  Its  secretion  is 
poured  into  the  month  by  from  seven  to  twenty  short  ducts 
(ductus  Riviniani),  which  open  upon  the  ridge  made  by  the 
gland  in  the  floor  of  the  mouth ;  the  larger  openings  being 
situated  by  the  side  of  the  fraenum  linguae.  One  of  the  ducts, 
longer  than  the  rest,  and  opening  close  to  Wharton's  duct,  has 
been  named  ductus  Bartholini. 

Fig.  45. 

THE  STYLOID  MUSCLES  AND 
THE  MUSCLES  OP  THE  TONGUE. — • 
1.  A  portion  of  the  temporal  bone 
of  the  left  side  of  the  skull  in- 
cluding the  styloid  and  mastoid 
processes,  and  the  meatus  a'udi- 
torius  externus.  2,  2.  The  right 
side  of  the  lower  jaw,  divided  at 
its  symphysis ;  the  left  side  having 
been  removed.  3.  The  tongue 
4.  The  genio-hyoideus  muscle.  5 
The  genio-hyo-glossus.  6.  The 
hyo-glossus  muscle  ;  its  basio-glos- 
sus  portion.  7.  Its  cerato-glossus 
portion.  8.  The  anterior  fibres 
of  the  lingualis  issuing  from  be- 
tween the  hyo-glossus  and  genio- 
hyo-glossus.  9.  The  stylo-glossus 
muscle,  with  a  small  portion  of  the 
stylo-maxillary  ligament.  10.  The 
stylo-hyoid.  11.  The  stylo-pha- 
ryngeus  muscle.  12.  The  os  hy- 
oides.  13.  The  thyro-hyoidean 
membrane.  14.  The  thyroid  car- 
tilage. 15.  The  thyrc-hyoideus 
muscle  arising  from  the  oblique 
line  on  the  thyroid  cartilage.  16.  The  cricoid  cartilage.  17.  The  crico-thy- 
roidean  membrane,  through  which  the  operation  of  laryngotomy  is  performed. 
18.  The  trachea.  19.  The  commencement  of  the  oesophagus. 

Fourth  Group. — Muscles  of  the  tongue. 

Genio-hyo-glossus, 

Hyo-glossus, 

Lingualis, 

Stylo-glossus, 
Palato-glossus. 

These  muscles  are  already  exposed  by  the  preparation  of  the  last 
group ;  the  student  has  therefore  only  to  clean  them,  to  bring  them  more 
clearly  into  view. 

The  genio-hyo-glossus  is  repeated  with  this  group,  as  belonging  in 
action  to  the  present  set  of  muscles  as  well  as  the  last. 

The  IJYO-GLOSSUS  is  a  square-shaped  plane  of  muscle,  arising 
from  the  whole  length  of  the  great  cornu  and  from  the  body  of 
the  QS  hyoides,  and  inserted  between  the  stylo-glossus  and  lin- 


PALATO-GLOSSUS.  151 

gualis  into  the  side  of  the  tongue.  The  direction  of  the  fibres  of 
that  portion  of  the  muscle  which  arises  from  the  body  is  obliquely 
backwards,  and  that  from  the  great  cornu  obliquely  forwards ; 
hence  they  are  described  by  Albinus  as  two  distinct  muscles, 
under  the  names  of  basio-glossus  and  cerato-glossus,  to  which  he 
added  a  third  fasciculus,  arising  from  the  lesser  cornu,  and 
spreading  along  the  side  of  the  tongue,  the  chondro-glossus. 
The  basio-glossus  slightly  overlaps  the  cerato-glossus  at  its  upper 
part,  and  is  separated  from  it  by  the  transverse  portion  of  the 
stylo-glossus. 

The  hyo-glossus  muscle  is  crossed  lay  two  large  nerves,  and  the  duct  of 
the  submaxillary  gland.  The  gustatory  nerve  is  the  highest  of  the  three, 
the  hypoglossal  nerve  the  lowest,  Wharton's  duct  and  the  deep  process 
of  the  submaxillary  gland  lying  between  them. 

The  LINGUALIS — The  fibres  of  this  muscle  (lingualis  inferior) 
may  be  seen  towards  the  apex  of  the  tongue,  issuing  from  the 
interval  between  the  hyo-glossus  and  genio-hyo-glossus ;  it  is 
best  examined  by  removing  the  preceding  muscle.  It  consists  of 
a  small  fasciculus  of  fibres,  running  longitudinally  from  the  base, 
where  it  is  attached  to  the  os  hyoides,  to  the  apex  of  the  tongue. 
By  the  outer  border  its  fibres  reach  the  plane  of  longitudinal  fas- 
ciculi of  the  stylo-glossus;  and  by  its  under  surface  it  is  in  rela- 
tion with  the  ranine  artery. 

The  STYLO-GLOSSUS  arises  from  the  apex  of  the  styloid  process 
and  from  the  stylo-maxillary  ligament;  it  divides  upon  the  side 
of  the  tongue  into  a  transverse  and  longitudinal  portion  :  the 
transverse  portion  dips  into  the  substance  of  the  tongue  between 
the  two  parts  of  the  hyo-glossus ;  the  longitudinal  portion  spreads 
out  upon  the  side  of  the  tongue,  and  is  prolonged  forward  as  far 
as  its  tip. 

The  PALATO-GLOSSUS  passes  between  the  soft  palate  and  the 
side  of  the  base  of  the  tongue,  forming  a  projection  of  the  mu- 
cous membrane,  which  is  called  the  anterior  pillar  of  the  soft 
palate.  Its  fibres  are  lost  superiorly  among  the  muscular  fibres 
of  the  palato-pharyngeus,  and  inferiorly  among  the  fibres  of  the 
stylo-glossus  upon  the  side  of  the  tongue.  This  muscle,  with  its 
fellow,  constitutes  the  constrictor  isthmi  faucium. 

ACTIONS. — The  genio-hyo-glossus  muscle  effects  several  movements  of 
the  tongue.  When  the  tongue  is  steadied  and  pointed  by  the  other 
muscles,  the  posterior  fibres  of  the  genio-hyo-glossus  would  dart  it  from 
the  mouth,  while  its  anterior  fibres  would  restore  it  to  its  original  posi- 
tion. The  whole  length  of  the  muscle  acting  upon  the  tongue,  would 
render  it  concave  along  the  middle  line,  and  form  a  channel  for  the  cur- 
rent of  fluid  towards  the  pharynx,  as  in  sucking.  The  apex  of  the  tongue 
is  directed  to  the  roof  of  the  mouth,  and  rendered  convex  from  before 
Ku-kwards  by  the  linguales.  The  hyo-glossi,  by  drawing  down  the  sides 
of  the  tongue,  render  it  convex  along  the  middle  line.  It  is  drawn  up- 


152  THE   DISSECTOR. 

wards  at  its  base  by  the  palato-glossi,  and  backwards  or  to  either  side 
by  the  stylo-glossi.  Thus  the  whole  of  the  complicated  movements  of 
the  tongue  may  be  explained,  by  reasoning  upon  the  direction  of  the 
fibres  of  the  muscles  and  their  probable  actions.  The  palato-glossi  mus- 
cles, assisted  by  the  uvula,  have  the  power  of  closing  the  fauces  com- 
pletely, an  action  which  takes  place  in  deglutition. 

VESSELS  AND  NERVES  OF  THE  NECK. 

Having  thus  far  studied  the  muscles,  the  dissector  should  turn  to  the 
opposite  side  of  the  neck,  with  the  view  of  examining  the  vessels  and 
nerves.  The  integument  and  superficial  fascia  having  been  dissected 
back,  the  platysma  is  brought  into  view,  and  may  be  carefully  raised. 
Beneath  it,  in  the  anterior  triangle,  will  be  found  the  inframaxillary 
branches  of  the  cervico-facial  division  of  the  facial  nerve  (page  127), 
and  the  superficialis  colli  nerve  ;  lying  upon  the  sheath  of  the  sterno- 
mastoid  muscle  is  the  auricularis  magnus  nerve  and  external  jugular 
vein,  with  one  or  two  lymphatic  glands ;  and  in  the  lower  part  of  the 
posterior  triangle  will  be  seen  the  clavicular  and  acromial  branches  of 
the  cervical  plexus. 

The  SUPERFICIALIS  COLLI  nerve,  one  of  the  three  superficial 
ascending  branches  of  the  cervical  plexus,  arises  from  the  second 
and  third  cervical  nerves,  and  curving  around  the  posterior  bor- 
der of  the  sterno-mastoid  at  about  its  middle,  crosses  that  muscle 
to  its  anterior  border ;  it  then  pierces  the  deep  cervical  fascia, 
and  divides  into  an  ascending  and  descending  branch.  There 
are  sometimes  two  nerves  in  place  of  this  division  into  two 
branches. 

The  ascending  branch  divides  into  several  filaments,  one  of 
which  ascends  by  the  side  of  the  external  jugular  vein;  others 
communicate  with  the  inframaxillary  branches  of  the  facial  nerve, 
forming  a  kind  of  plexus  ;  and  a  third  set  piercing  the  platysma 
are  distributed  to  the  integument  of  the  anterior  triangle  as 
high  as  the  lower  jaw.  These  latter  supply  the  platysma,  and 
communicate  with  the  branches  of  the  facial  through  that 
muscle. 

The  descending  branch  pierces  the  platysma,  and  is  distributed 
to  the  integument  of  the  front  of  the  neck  as  far  downwards  as 
the  sternum. 

The  AURICULARIS  MAGNUS,  the  largest  of  the  three  branches  of 
the  cervical  plexus,  proceeds  from  the  second  and  third  cervical 
nerves.  It  pierces  the  deep  fascia  at  the  posterior  border  of  the 
sterno-mastoid,  and  ascends  beneath  the  platysma  and  parallel 
with  the  external  jugular  vein  to  the  parotid  gland,  where  it 
divides  into  an  anterior  and  posterior  branch. 

The  anterior  branch  distributes  filaments  to  the  integument  of 
the  face  over  the  parotid  gland,  and  communicates  with  the  facial 
nerve. 

The  posterior  branch  ascends  to  the  back  of  the  ear,  and  divides 


ANTERIOR  JUGULAR  VEIN.  153 

into  filaments  which  are  distributed  to  the  pinna ;  and  a  mastoid 
branch  which  supplies  the  integument  behind  the  ear,  and  com- 
municates with  the  posterior  auricular  branches  of  the  pneumo- 
gastric  and  facial  nerve,  and  with  the  occipitalis  minor. 

The  OCCIPITALIS  MINOR  nerve,  arising  from  the  second  cervical 
nerve,  ascends  along  the  posterior  border  of  the  sterno-mastoid, 
pierces  the  deep  fascia  near  the  occiput,  and  is  distributed  to  the 
occipito-frontalis  and  attollens  aurem  (auricular  branch),  and  to 
the  lateral  and  posterior  part  of  the  head,  communicating  with 
the  occipitalis  major  and  posterior  auricular  branch  of  the  facial. 

The  EXTERNAL  JUGULAR  VEIN,  formed  by  the  union  of  the 
posterior  auricular  and  temporo-maxillary  vein  in  the  parotid 
gland,  descends  over  the  sterno-mastoid  muscle,  lying  between 
the  deep  cervical  fascia  and  the  platysma,  to  the  posterior  border 
of  the  sterno-mastoid,  at  its  lower  part,  where  it  pierces  the  deep 
fascia  and  terminates  in  the  subclavian  vein.  It  communicates 
with  the  internal  jugular  vein  in  the  parotid  gland,  and  in  the 
lower  part  of  the  neck  with  the  anterior  jugular.  It  also  com- 
municates occasionally  with  the  cephalic  vein,  by  a  branch  from 
the  latter  which  crosses  the  clavicle.  The  external  jugular  vein 
receives  several  superficial  veins  from  the  back  part  of  the  head 
and  neck. 

Operation. — The  external  jugular  vein  is  generally  opened,  where  it  lies 
on  the  sterno-mastoid  muscle.  The  finger  should  be  placed  on  the  vessel, 
below  the  point  selected  for  incision,  with  the  double  object  of  rendering 
the  vein  tense,  and  preventing  the  admission  of  air.  The  incision  should 
be  directed  obliquely  upwards  and  backwards  (Fig.  44,  No.  10),  so  as  to 
(KISS  the  direction  of  the  fibres  of  the  platysma,  otherwise  the  fibres,  by 
drawing  the  edges  of  the  wound  together,  might  prevent  the  flow  of  blood. 
The  parts  cut  through  will  be  the  integument,  the  platysma  with  the  two 
layers  of  the  superficial  fascia,  between  which  it  is  placed,  and  the  coats 
of  the  vein. 

The  ANTERIOR  JUGULAR  VEIN  is  formed  by  branches  which 
commence  in  the  fore  part  of  the  neck.  It  passes  along  the  an- 
terior border  of  the  sterno-mastoid,  and  turning  outwards  behind 
the  tendon  of  that  muscle,  terminates  in  the  subclavian  vein  near 
the  external  jugular.  It  communicates  with  the  external  and 
internal  jugular  vein,  and  with  its  fellow  of  the  opposite  side  of 
the  neck. 

Superficial  Lymphatic  Glands. — The  superficial  lymphatic 
glands  of  the  neck  are  two  or  three  beneath  the  chin  and  in  the 
submaxillary  triangle,  and  three  or  four  in  the  course  of  the  ex- 
ternal jugular  vein.  The  largest  of  the  latter  are  situated  at  the 
lower  part  of  the  vein,  at  the  posterior  border  of  the  sterno-mastoid 
muscle.  • 


154  THE   DISSECTOR. 


POSTERIOR  TRIANGULAR  SPACE. 

• 

The  sheath  of  the  sterno-mastoid  may  now  be  laid  open  by  means  of  a 
longitudinal  incision,  and  dissected  back  to  the  posterior  border  of  the 
muscle.  In  the  next  place,  the  deep  fascia  covering  the  posterior  trian- 
gular space  should  be  carefully  removed,  in  order  to  bring  into  view  the 
nerves  and  vessels  which  it  contains.  Turning  around  the  posterior 
border  of  the  sterno-mastoid  from  behind,  are  the  three  ascending  branches 
of  the  cervical  plexus  already  described,  namely,  superficialis  colli,  auri- 
cularis  magnus,  and  occipitalis  minor;  crossing  the  space  below  these, 
is  the  spinal  accessory  nerve  in  its  course  from  the  sterno-mastoid  to  the 
trapezius  ;  lower  down  are  the  descending  branches  of  the  cervical  plexus, 
claviculares,  and  acromiales  ;  beneath  the  latter  is  the  posterior  belly  of 
the  omo-hyoid  muscle,  which  marks  the  lower  boundary  of  the  occipital 
triangle,  and  the  upper  boundary  of  the  subclavian  triangle.  On  a  level 
with  this  muscle  is  the  transversalis  colli  artery,  and  lower  down,  behind 
the  clavicle,  the  suprascapular  artery.  Moreover,  lying  deeply  in  the 
subclavian  triangle,  is  the  subclavian  artery  and  brachial  plexus  of 
nerves. 

The  subclavian  triangle  varies  in  its  extent  in  different  subjects  ;  the 
posterior  belly  of  the  omo-hyoideus,  usually  an  inch  and  a  half  above  the 
clavicle,  may  descend  nearer  to  that  bone ;  or  the  sterno-mastoid  and 
trapezius,  instead  of  having  between  them  a  space  equal  to  one-third  the 
length  of  the  clavicle,  may  approach  each  other,  or  even  meet. 

The  floor  of  the  posterior  triangle  is  formed  by  the  muscles  of  the  back 
of  the  neck,  and  by  the  middle  and  posterior  scalenus. 

After  studying  the  relative  position  of  the  contents  of  the  posterior  tri- 
angle, the  sterno-mastoid  may  be  divided  through  the  middle,  and  its 
ends  turned  upwards  and  downwards.  The  spinal  accessory  nerve  may 
then  be  seen  piercing  the  upper  part  of  the  muscle,  and  the  cervical 
nerves  and  cervical  plexus  may  be  dissected. 

CERVICAL  NERVES. — The  cervical  nerves  are  eight  in  number, 
the  first  passing  out  of  the  vertebral  canal  above  the  atlas,  and 
the  last  between  the  seventh  cervical  and  first  dorsal  vertebra. 
Each  nerve,  at  its  issue  from  the  vertebral  canal,  splits  into  an 
anterior  and  posterior  division.  The  posterior  divisions  have  been 
already  described. 

The  anterior  division  of  the  first  cervical,  or  suboccipital 
nerve,  proceeds  from  its  trunk,  while  the  latter  is  placed  on  the 
posterior  arch  of  the  atlas;  and  passing  forwards,  beneath  the 
vertebral  artery,  curves  downwards,  in  front  of  the  transverse 
process  of  the  atlas,  to  form  a  loop  of  communication  with  an 
ascending  branch  of  the  second  cervical  nerve. 

This  nerve  supplies  the  rectus  lateralis  and  rectus  anticus 
minor  muscle,  and  its  loop  receives  branches  of  communication 
from  the  pneumogastric,  hypoglossal,  and  sympathetic  nerve. 

The  anterior  division  of  the  second  cervical  nerve  quits  its 
trunk  of  origin  by  passing  over  the  lamina  of  the  axis;  it  then 
passes  forwards  externally  to  the  vertebral  artery  and  intertrans- 
verse  muscles,  and  divides  into  an  ascending  branch,  which  com- 


ANTERIOR  CERVICAL  NERVES.  155 

pletes  the  loop  with  the  first  nerve,  and  two  descending  branches, 
which  form  loops  with  corresponding  branches  of  the  third. 

The  third  and  fourth  cervical  nerves,  immediately  on  their  exit 
from  between  the  intertransverse  muscles,  divide  in  a  similar 
manner  into  branches  which  form  loops  with  the  nerve  above 
and  below. 

Cervical  Plexus.  —  The  communications  so  established  between 
the  anterior  divisions  of  the  four  upper  cervical  nerves,  consti- 
tute the  cervical  plexus.  The  plexus  is  situated  behind  the 
sterno-mastoid  muscle,  and  rests  on  the  levator  anguli  scapulae, 
posterior  and  middle  scalenus,  and  splenius  colli  muscle. 

The  branches  of  the  cervical  plexus  admit  of  a  primary  divi- 
sion into  superficial  and  deep  ;  and  the  superficial  set  are  further 
divisible  into  ascending  and  descending.  The  following  table 
exhibits  this  arrangement  :  — 

(  Superficial  is  colli, 
/-  Ascending,    -j  Auricularis  magnus, 
Superficial  .     .    J  (  Occipitalis  minor. 


f  Communicating  branches, 
Communicans  noni, 
Muscular, 
Phrenic. 

The  ascending  superficial  branches  proceed  from  the  second 
and  third  cervical  nerves,  and  pass  forwards  to  the  posterior 
border  of  the  sterno-mastoid  muscle  (p.  152). 

The  descending  superficial  branches,  two  or  three  in  number, 
proceed  from  the  fourth  cervical  nerve,  and  pass  downwards  in 
the  triangular  space  ;  they  then  pierce  the  deep  fascia,  and  cross- 
ing the  clavicle,  are  distributed  to  the  integument  of  the  front  of 
the  chest  from  the  sternum  to  the  acromion  :  hence  their  desig- 
nation, claviculares  and  acromiales.  The  most  anterior  of  the 
branches  is  named  sternal,  from  its  destination,  and  the  outer- 
most branch  passes  over  the  clavicular  attachment  of  the  trape- 
zius  to  reach  the  shoulder. 

Deep  Branches.  —  The  communicating  branches  are  filaments 
of  communication  passing  between  the  loop  of  the  first  cervical 
nerve  and  the  pneuinogastric,  hypoglossal,  and  sympathetic 
nerve,  and  communications  between  the  other  nerves  and  the 
sympathetic. 

The  communicans  noni  is  a  long  and  slender  branch  of  com- 
munication between  the  cervical  plexus  and  the  descendens  noni. 
It  arises  from  the  second  and  third  cervical  nerves,  and  passing 


156  THE   DISSECTOR. 

downwards,  by  the  side  of  the  internal  jugular  vein  to  the  middle 
of  the  neck,  reaches  the  front  of  the  sheath  of  the  carotid  vessels, 
and  forms  a  loop  with  the  descendens  noni  of  the  hypoglossal  nerve. 

The  muscular  branches  of  the  cervical  plexus  are  distributed 
to  the  muscles  of  the  front  of  the  vertebral  column  and  side  of 
the  neck.  From  the  loop,  between  the  first  and  second  nerve, 
branches  are  given  to  the  anterior  recti.  From  the  second  cer- 
vical nerve  a  branch  is  given  to  the  sterno-mastoid.  From  the 
third  and  fourth  nerves  branches  are  given  off  to  the  trapezius, 
levator  anguli  scapulae,  and  scalenus  posticus.  The  branch  to 
the  trapezius  communicates  with  the  spinal  accessory  nerve. 

The  phrenic  nerve  (internal  respiratory  of  Bell)  is  formed  by 
the  union  of  filaments  from  the  third,  fourth,  and  fifth  cervical 
nerve.  It  passes  downwards,  resting  on  the  scalenus  anticus 
muscle,  and  at  the  root  of  the  neck  receives  a  filament  from  the 
sympathetic.  The  nerve  next  passes  between  the  subclavian 
artery  and  vein,  and  crossing  the  origin  of  the  internal  mammary 
artery,  enters  the  chest.  It  then  descends  through  the  chest, 
between  the  pleura  and  pericardium,  and  in  front  of  the  root  of 
the  lung,  to  the  diaphragm  (page  105). 

BRACHIAL  PLEXUS. — The  anterior  divisions  of  the  four  lower 
cervical  nerves  and  the  first  dorsal  constitute,  by  their  commu- 
nications, the  brachial  plexus.  The  mode  of  formation  of  the 
plexus  is  as  follows  :  The  fifth  and  sixth  nerves  unite  to  form  a 
common  trunk.  The  last  cervical  and  first  dorsal  also  unite  as 
soon  as  they  meet  to  form  a  single  trunk  ;  the  seventh  cervical 
nerve  lies  for  some  distance  apart  from  the  rest,  and  then  divides 
into  two  branches,  which  join  the  other  cords.  At  this  point, 
the  plexus  consists  of  two  cords,  from  which  a  third  is  given  off ; 
and  the  three  cords  become  placed,  one  to  the  inner  side  of  the 
axillary  artery,  one  behind,  and  one  to  its  outer  side. 

The  brachial  plexus  communicates  with  the  cervical  plexus  by 
means  of  a  branch  from  the  fourth  to  the  fifth  nerve,  and  receives 
branches  from  the  two  inferior  cervical  ganglia  of  the  sympathetic. 

The  branches  of  the  brachial  plexus  in  the  neck  are  some  small 
branches  to  the  longus  colli  and  scaleni ;  branches  to  the  rhom- 
boidei  and  subclavius  muscle,  the  suprascapular  and  posterior 
thoracic. 

The  rhomboid  branch  proceeds  from  the  fifth  cervical  nerve, 
and,  passing  backwards  through  the  fibres  of  the  scalenus  medius, 
and  beneath  the  levator  anguli  scapula,  is  distributed  to  the 
under  surface  of  the  rhomboid  muscles  ;  in  its  course,  it  some- 
times gives  a  branch  to  the  levator  anguli  scapulae. 

The  subclavian  branch  proceeds  from  the  cord  formed  by  the 
fifth  and  sixth  nerves,  and  descends  in  front  of  the  subclavian 


SUBCLAVIAN    ARTERY. 


157 


artery  to  the  subclavius  muscle ;  this  nerve  usually  communicates 
with  the  phrenic  at  its  entrance  into  the  chest. 

The  posterior  thoracic  nerve  (long  thoracic  ;  external  respira- 
tory of  Bell)  arises  by  two  roots  from  the  fifth  and  sixth  cervical 
nerves,  and,  passing  between  the  fibres  of  the  middle  scalenus, 
descends  behind  the  brachial  plexus  to  the  serratus  magnus,  along 
which  it  is  distributed  to  the  lower  border  of  that  muscle. 

The  suprascapular  nerve  proceeds  from  the  fifth  cervical  nerve, 
and  descends  beneath  the  trapezius  to  the  suprascapular  fossa. 

Before  proceeding  to  the  study  of  the  subclavian  artery  and  its  branches, 
the  dissector  should  define  and  examine  a  group  of  muscles  forming  a 
pyramidal  mass  at  the  root  of  the  neck,  the  scaleni ;  these  muscles  are 
connected  with  the  transverse  processes  of  the  cervical  vertebrae  above, 
and  the  first  and  second  ribs  below.  According  to  different  authors,  they 
are  two,  three,  or  more  in  number. 

The  SCALENUS  ANTICUS  arises  from  the  anterior  tubercles  of  the 
transverse  processes  of  the  third,  fourth,  fifth,  and  sixth  cervical 
vertebra;,  and  is  inserted  into  the  tubercle  upon  the  upper  and 
inner  border  of  the  first  rib ;  it  is  a  triangular  muscle,  and  at  its 
oriirin  is  continuous  with  the  rectus  anticus  major. 

The  SCALENUS  POSTICUS  (scalenus  medius  and  posticus)  arises 
from  the  posterior  tubercles  of  all  the  cervical  vertebrae  excepting 
the  first ;  it  is  inserted  by  two  fleshy  fasciculi  into  the  first  and 
second  ribs.  The  anterior  of  the  two  fasciculi  (scalenus  medius) 
is  large,  and  occupies  all  the  surface  of  the  first  rib  between  the 


Fig.  46. 


THE  ARCH  OP  THE  AORTA,  WITH  ITS 
BRANCHES,  AND  THE  COURSE  OF  THE 
SUBCLAVIAN  ARTERIES. — 1.  The  ascend- 
ing norta.  2.  Its  arch.  3.  The  descend- 
ing aorta.  4.  The  arteria  innominata.  5. 
The  right  subclavian,  the  first  or  obliquely 
ascending  portion  of  its  course.  6.  The 
second,  or  transverse  portion.  7.  The 
third,  or  obliquely  descending  portion. 
8.  The  right  carotid  artery.  9.  The  left 
carotid.  10.  The  left  subclavian  artery  ; 
the  first,  or  perpendicular  portion.  11. 
The  second,  or  transverse.  12.  The  third, 
or  oblique  portion.  13.  The  right  pneu- 
mogastric  nerve,  giving  off  the  recurrent  * 
around  the  subclavian  artery.  14.  The 
left  pneumogastric,  sending  its  recurrent 
branch  *  around  the  arch  of  the  aorta. 
**  The  two  recurrent  laryngeal  nerves. 


groove  for  the  subclavian  artery  and  the  tuberosity.  The  poste- 
rior (scalenus  posticus)  is  small,  and  is  attached  to  the  second  rib 
between  its  tubercle  and  angle. 

SUBCLAVIAN  ARTERY  and  its  Branches. — The  subclavian  artery 
14 


158      •  THE  DISSECTOR.  ^ 

differs  in  its  origin  on  the  two  sides  of  the  body,  and  consequently 
in  that  portion  of  its  course  which  is  in  relation  with  the  cavity 
of  the  thorax.  Qn  its  escape  from  the  chest,  its  course  Is  alike 
on  both  sides ;  the  course  of  the  artery  is  divided  into  three 
parts. 

First  Part. — On  the  right  side  the  subclavian  artery  com- 
mences at  the  bifurcation  of  the  arteria  innominata,  opposite  the 
sterno-clavicular  articulation,  and  passes  obliquely  outwards  to 
the  inner  border  of  the  scalenus  anticus,  where  the  second  por- 
tion of  its  course  begins. 

On  the  left  side  the  subclavian  artery  proceeds  from  the  pos- 
terior part  of  the  arch  of  the  aorta,  and  therefore  lies  more 
deeply  in  the  chest,  and  is  longer  in  its  course.  It  ascends  per- 
pendicularly to  the  inner  border  of  the  scalenus  anticus.  From 
this  point  the  arteries  correspond  on  both  sides. 

Second  Part. — The  artery  next  passes  horizontally  outwards 
behind  the  scalenus  anticus  ;  and  (third  part)  then  curves  out- 
wards and  downwards  to  become,  opposite  the  lower  border  of 
the  first  rib,  the  axillary  artery. 

Relations. — The  first  part  of  the  artery  is  crossed  in  front  by 
the  internal  jugular  vein,  vertebral  vein,  pneumogastric  nerve, 
phrenic  nerve,  and  one  or  two  branches  of  the  sympathetic ; 
behind  it  has  the  sympathetic  nerve,  on  the  right  side  the  recur- 
rent nerve,  and  on  the  left  the  thoracic  duct ;  below,  on  the  right 
side  is  the  pleura ;  that  membrane  being  to  its  outer  side  on  the 
left. 

The  second  portion  of  the  artery  has  the  scalenus  anticus  in 
front;' the  scalenus  medius  and  two  lower  nerves  of  the  bjachial 
plexus  behind;  the  upper  nerves  of  the  plexus  above,  and  the 
pleura  below.  The  scalenus  anticus  separates  it  from  the  phrenic 
nerve  and  subclavian  vein,  which  latter  is  rather  below  the  level 
of  the  artery. 

The  third  portion  of  the  artery  is  situated  in  the  subclavian 
triangle,  and  is  more  superficial  than  the  rest.  In  front  it  is 
covered  by  the  integument,  platysma,  and  deep  fascia,  and 
crossed  by  the  supraclavicular  nerves.  Lower  down  it  is  crossed 
by  the  suprascapular  artery  and  vein,  and  gets  behind  the  sub- 
clavius  muscle  and  clavicle.  Behind,  it  has  the  scalenus  medius  ; 
above,  the  brachial  plexus ;  and  below,  the  first  rib  and  subcla- 
vian vein. 

Operation. — Ligature  of  the  subclavian  artery  is  performed  on  that 
vessel  in  the  third  part  of  its  course,  just  after  its  issue  from  between 
the  scaleni  muscles,  and  where  it  rests  on  the  first  rib. 

An  incision  is  made  along  the  upper  border  of  the  clavicle,  from  the 
sternal  portion  of  the  sterno-mastoid  muscle  to  the  edge  of  the  trapezius. 
This  should  divide  the  integument,  superficial  fascia,  platysma,  and  deep 


VERTEBRAL  ARTERY.  159 

fascia ;  and  more  or  less  of  the  clavicular  portion  of  the  sterno-mastoid 
muscle,  according  to  its  breadth  or  the  depth  of  the  artery.  Then  lay 
aside  the  knife,  introduce  a  finger  into  the  wound  behind  the  vein, 
and  feel  for  the  tubercle  on  the  first  rib  :  immediately  behind  it  is  the 
cylinder  of  the  artery,  which  may  be  recognized  by  its  roundness  and 
elasticity,  and  by  its  pulsation  beneath  the  finger.  One  of  the  chief 
difficulties  in  the  performance  of  the  operation  is  the  position  of  the  vein, 
in  front  of  the  artery  ;  and  when  of  large  size  and  distended  with  blood 
it  may  present  an  inconvenient  obstacle.  Occasionally  another  impedi- 
ment arises  from  the  termination  of  the  external  jugular  vein  in  the 
middle  of  the  space.  The  operator  has  to  gnard  against  wounding  these 
veins,  or  placing  his  ligature  around  any  of  the  nerves  of  the  brachial 
]  ilex  us.  The  parts  cut  through  in  the  operation  are  the  integument,  snper- 
Jicial  fascia,  platysma,  supraclavicular  nerves,  clavicular  origin  of  the 
sterno-mastoid  muscle,  deep  fascia,  cellular  tissue. 

Branches. — The  branches  of  the  subclavian  artery  are  four, 
and  sometimes  five,  in  number.     Three  are  given  off  from  the 
first  portion  of  the  artery  ;  one,  the  superior  intercostal,  from  the 
second  portion  ;  and  when  a  fifth  artery  exists,  it  arises  from  the 
third  portion,  and  is  the  suprascapular.     In  a  tabular  form  the 
branches  are  as  follows  : — 
Vertebral, 
Internal  mammary, 

f  Inferior  thyroid, 
Thyroid  axis  <  Suprascapular, 

[  Transversalis  colli. 
Superior  intercostal — Profunda  cervicis. 

The  VERTEBRAL  ARTERY,  the  first  and  largest  of  the  branches 
of  the  subclavian  artery,  arises  from  the  posterior  aspect  of  that 
trunk  ;  it  ascends  through  the  foramina  in  the  transverse  processes 

THE    SUBCLAVIAN    ARTERY,    WITH    ITS  Fig.  47. 

BRANCHES. — 1.  The  arteria  innominate,  di- 
viding into,  2.  The  right  common  carotid  ar- 
tery, and  3.  The  right  subclavian  artery,  the 
first  part  of  its  course,  from  which  all  the 
branches  are  given  off.  4.  The  second  part 
of  its  course.  5.  The  third  part  of  its  course. 
6,  7.  The  two  visceral  branches  of  the  subcla- 
vian artery  :  6.  The  vertebral.  7.  The  infe- 
rior thyroid.  8.  The  thyroid  axis,  giving  off 
its  four  branches.  9,  10.  The  two  cervical 
branches  of  the  subclavian  :  9.  The  cervi- 
calis  superficialis.  10.  The  cervicalis  profun- 
da.  11,  12.  The  two  scapular  branches  : 
11.  The  posterior  scapular.  12.  The  supra- 
scapular.  13,  14.  The  two  thoracic  branches  : 
13.  The  internal  mammary  artery.  14.  The 
superior  intercostal. 

of  all  the  cervical  vertebrae,  excepting  the  last ;  then  winds  back- 
wards around  the  articulating  process  of  the  atlas  ;  and,  piercing 


160  THE   DISSECTOR. 

the  dura  mater,  enters  the  skull  through  the  foramen  magnum. 
The  two  arteries  unite  at  the  lower  border  of  the  pons  Varolii, 
to  form  the  basilar  artery.  In  the  foramina  of  the  transverse 
processes  of  the  vertebrae  the  artery  lies  in  front  of  the  cervical 
nerves,  and  on  the  left  side  the  artery  is  crossed  by  the  thoracic 
duct. 

The  branches  of  the  vertebral  artery  in  the  neck  are  lateral 
spinal  branches,  which  enter  the  intervertebral  foramina,'  and  are 
distributed  to  the  vertebra  and  spinal  cord. 

The  INTERNAL  MAMMARY  ARTERY  arises  from  the  under  side  of 
the  subclavian,  and  passes  down  behind  the  subclavian  vein  to 
the  cartilage  of  the  first  rib.  It  then  descends  by  the  side  of  the 
sternum,  resting  on  the  cartilages  of  the  ribs,  to  the  sheath  of 
the  rectus,  where,  under  the  name  of  superior  epigastric,  it  ter- 
minates by  inosculating  with  the  epigastric  branch  of  the  exter- 
nal iliac.  As  the  artery  enters  the  chest  it  is  crossed  by  the 
phrenic  nerve. 

The  relations  and  branches  of  the  internal  mammary  artery 
are  described  in  Chapter  VII. 

The  THYROID  AXIS  is  a  short  trunk  which  arises  from  the  front 
of  the  subclavian,  close  to  the  inner  border  of  the  anterior  scalenus, 
and  divides  almost  immediately  into  three  branches;  inferior  thy- 
roid, suprascapular,  and  trans versalis  colli. 

The  INFERIOR  THYROID  ARTERY  ascends  obliquely  in  a  serpen- 
tine course  behind  the  sheath  of  the  carotid  vessels,  and  in  front 
of  the  longus  colli,  to  the  inferior  and  posterior  part  of  the  thy- 
roid gland,  to  which  it  is  distributed.  It  is  in  relation  with  the 
middle  cervical  ganglion  of  the  sympathetic,  which  lies  in  front 
of  it ;  and  sends  branches  to  the  trachea,  larynx,  and  O3so- 
phagus. 

Near  its  origin  the  inferior  thyroid  artery  gives  off  a  large 
branch,  the  cervicalis  ascendens,  which  passes  up  the  neck,  rest- 
ing on  the  anterior  tubercles  of  the  transverse  processes  of  the 
cervical  vertebrae,  and  occupying  the  groove  between  the  scale- 
nus anticus  and  rectus  anticus  major.  It  is  distributed  to  the 
deep  muscles  and  glands  of  the  neck,  and  sends  branches  through 
the  intervertebral  foramina  to  supply  the  spinal  cord  and  its 
membranes. 

The  SUPRASCAPULAR  ARTERY  (transversalis  humeri)  passes  ob- 
liquely outwards  behind  the  clavicle,  and  over  the  ligament  of 
the  suprascapular  notch,  to  the  supraspinatus  fossa.  It  crosses 
in  its  course  the  scalenus  anticus  muscle,  phrenic  nerve,  and  sub- 
clavian artery,  is  distributed  to  the  muscles  of  the  dorsum  of  the 
scapula,  and  inosculates  with  the  posterior  scapular,  and  beneath 
the  acromion  process  with  the  dorsal  branch  of  the  subscapular 
artery. 


COMMON  CAROTID  ARTERY.  161 

The  TRANSVERSALTS  coLLi  ARTERY  passes  transversely  across  the 
subclavian  triangle  at  the  root  of  the  neck  to  the  anterior  bor- 
der of  the  levator  anguli  scapulae,  where  it  divides  into  two  ter- 
minal branches,  the  superficialis  cervicis  and  posterior  scapular. 
In  its  course  it  lies  above  the  suprascapular  artery,  and  crosses 
the  scaleni  muscles  and  brachial  plexus  of  nerves,  often  passing 
between  the  latter.  At  its  bifurcation  it  is  covered  in  by  the 
edge  of  the  trapezius. 

The  superficialis  cervicis  artery,  its  ascending  branch,  passes 
upwards  under  cover  of  the  anterior  border  of  the  trapezius,  and 
is  distributed  to  the  superficial  muscles  of  the  neck  and  deep 
cervical  glands. 

The  posterior  scapular  artery,  the  proper  continuation  of  the 
transversalis  colli,  passes  backwards  to  the  superior  angle  of  the 
scapula,  and  then  descends  along  the  posterior  border  of  that 
bone  to  its  inferior  angle,  where  it  inosculates  with  the  subsca- 
pular  artery. 

The  SUPERIOR  INTERCOSTAL  ARTERY  arises  from  the  upper  and 
back  part  of  the  subclavian  artery  behind  the  scalenus  anticus, 
and  passes  down  behind  the  pleura  to  the  neck  of  the  first  rib, 
whence  it  descends  to  supply  the  first  two  intercostal  spaces. 

The  profunda  cervicis  artery  arises  by  a  common  trunk  with 
the  preceding,  or,  more  properly,  is  a  branch  of  the  superior 
intercostal,  corresponding  with  the  posterior  branch  of  the  other 
intercostal  arteries.  It  passes  backwards  between  the  transverse 
processes  of  the  seventh  cervical  and  first  dorsal  vertebra,  and 
ascends  among  the  muscles  at  the  back  of  the  neck,  to  which  it 
is  distributed,  inosculating  with  the  princeps  cervicis,  a  branch 
of  the  occipital. 

The  SUBCLAVIAN  VEIN,  the  continuation  upwards  of  the  axil- 
lary vein,  commences  opposite  the  lower  border  of  the  first  rib, 
and  ascends  in  front  of  the  rib  and  scalenus  anticus  and  behind 
the  clavicle  and  subclavius  muscle  to  opposite  the  sterno-clavicu- 
lar  articulation,  where  it  joins  with  the  internal  jugular  vein  to 
form  the  vena  innominata.  The  subclavian  vein  is  placed  in 
front  of,  but  rather  below,  the  level  of  the  subclavian  artery,  and 
is  separated  from  the  artery  by  the  scalenus  anticus,  and  by  the 
phrenic  and  pneumogastric  nerve. 

The  branches  which  open  into  the  subclavian  vein  are  the 
external  and  anterior  jugular  externally  to  the  scalenus  anticus, 
and  the  vertebral  internally  to  that  muscle. 

Carotid  Artery  and  its  Branches. 

The  COMMON  CAROTID  ARTERY  differs  in  its  origin  and  length 
on  two  sides  of  the  neck.  On  the  right  side  it  proceeds  from  the 

14* 


162 


THE   DISSECTOR. 


bifurcation  of  the  arteria  innominata  opposite  the  sterno-clavicu- 
lar  articulation  ;  on  the  left  it  arises  from  the  arch  of  the  aorta, 

Fig.  48. 


THE  CAROTID  AR- 
TERIES WITH  THE 
BRANCHES  OP  THE  EX- 
TERNAL CAROTID.  —  1. 
The  common  carotid. 

2.  The  external  carotid. 

3.  The  internal  carotid. 

4.  The  carotid  foramen 
in  the  petrous  portion  of 
the  temporal  bone.      5. 
The  superior  thyroid  ar- 
tery. 6.  The  lingual  arte- 
ry.  7.  The  facial  artery. 
8.  The  mastoid  artery.  9, 
The  occipital.     10.  The 
posterior  auricular.     11. 
The  transverse  facial  ar- 
tery.    12.   The  internal 
maxillary.  13.  The  tem- 
poral.    14.  The  ascend- 
ing pharyngeal  artery. 


and  ascending  to  a  parallel  position  in  the  neck,  takes  a  course 
similar  to  the  right. 

The  common  carotid  artery  ascends  the  neck  by  the  side  of 
the  trachea  and  larynx  to  a  point  corresponding  with  the  upper 
border  of  the  thyroid  cartilage,  where  it  divides  into  the  external 
carotid  and  internal  carotid. 

In  its  course  it  is  inclosed  in  a  fibrous  sheath,  which  also  con- 
tains the  internal  jugular  vein,  lying  to  the  outer  side  of  the 
artery ;  and  the  pneumogastric  nerve,  which  lies  between  and 
behind  both.  The  sheath  rests  upon  the  vertebral  column, 
having  interposed  the  sympathetic  nerve  and  the  muscles  of  the 
anterior  surface  of  the  vertebral  column,  namely,  the  longus  colli 
and  rectus  anticus  major.  In  front  of  the  sheath,  at  its  middle, 
is  the  loop  formed  between  the  descendens  noni  nerve  and  the 
communicating  branch  of  the  cervical  plexus,  with  the  filaments 
given  off  by  the  loop. 

With  regard  to  the  surface  of  the  neck,  the  sheath  of  the  caro- 
tid is  deeply  seated  in  the  lower  two-thirds  of  its  extent,  and 
superficially  in  its  upper  third.  It  is  covered  in  below  by  the 


COMMON   CAROTID   ARTERY.  163 

sterno-mastoid,  sterno-hyoid,  and  sterno-thyroid  muscles,  and 
crossed  at  about  its  middle  by  the  omo-hyoid.  Above,  it  has  in 
front  only  the  platysma  and  deep  fascia.  It  is  also  crossed,  both 
its  superficial  and  deep  part,  by  the  thyroid  veins. 

Lying  internally  to  the  sheath  is  the  trachea  and  larynx, 
with  the  inferior  thyroid  artery  and  recurrent  laryngeal  nerve, 
the  two  latter  reaching  that  situation  after  having  passed  behind 
the  sheath.  On  the  left  side  of  the  neck,  there  is  in  addition  the 
oesophagus.  Externally  to  the  sheath  is  a  chain  of  lymphatic 
vessels  and  glands,  the  concatenated  glands  of  the  neck. 

The  special  relations  of  the  left  common  carotid  while  within 
the  chest  are  described  in  Chapter  VI.  It  is  crpssed  by  the 
left  vena  innominata,  and  in  its  course  to  the  side  of  the  neck 
rests  upon  the  trachea,  oesophagus,  and  thoracic  duct. 

The  common  carotid  artery  gives  off  no  branch  in  its  course. 

The  sheath  of  the  carotid  artery  may  now  be  carefully  opened,  and  the 
relative  positions  of  the  internal  jugular  vein  and  pneumogastric  nerve 
examined. 

Operations. — The  common  carotid  artery  may  be  secured  either  in  the 
upper  or  the  lower  carotid  triangle.  In  the  former,  the  high  operation, 
the  artery  is  comparatively  superficial,  and  the  operation  proportionately 
simple.  The  incision  is  to  be  made  along  the  anterior  border  of  the 
sterno-mastoid,  commencing  an  inch  below  the  angle  of  the  jaw,  and 
carrying  it  half  way  down  the  neck.  It  should  divide  the  integument, 
superficial  fascia,  platysma,  and  deep  fascia.  We  then  expose  the  sheath 
of  the  vessels,  upon  which  lies  the  descendens  noni  nerve.  Leave  this 
nerve  undisturbed,  and  open  the  sheath  to  its  inner  side,  immediately 
above  the  omo-hyoid  muscle ;  then  turn  the  needle  around  the  artery 
from  without  inwards,  guarding  against  including  the  pneumogastric  nerve 
by  keeping  the  point  of  the  instrument  close  to  the  cylinder  of  the  artery. 
The  parts  to  be  cut  through  are  the  integument,  superficial  fascia,  platysma, 
superficialis  colli  nerve,  deep  fascia,  and  sheath  of  the  vessels. 

In  the  inferior  carotid  triangle,  the  low  operation  is  practised.  The 
sterno-mastoid  is  still  the  guide  for  the  incision,  and  the  layers  to  be 
cut  through  are  precisely  the  same  as  in  the  high  operation.  The 
sterno-mastoid  is  to  be  drawn  aside,  and  the  sheath  will  be  found  con- 
cealed by  the  sterno-thyroid  muscle.  This  muscle  is  to  be  divided,  and 
the  sheath  opened  as  in  the  previous  operation.  The  descendens  noni, 
if  it  extend  so  low,  lies  to  the  inner  side  of  the  sheath.  The  anterior 
jugular  vein  is  situated  along  the  inner  border  of  the  sterno-mastoid 
muscle,  and  should  be  looked  for  and  avoided.  The  parts  to  be  cut 
through  are  the  same  as  in  the  previous  operation,  with  the  addition  of 
the  sterno-thyroid  muscle. 

The  arteria  innominata  is  also  tied  in  the  lower  carotid  triangle,  on  the 
right  side.  The  incision,  three  inches  in  length,  should  be  made  ob- 
liquely across  the  space  between  the  two  sterno-mastoid  muscles,  imme- 
diately above  the  sternum.  It  should  commence  over  the  right  sterno- 
clavicular  articulation,  and  be  carried  obliquely  upwards  to  the  sterno- 
mastoid  muscle  of  the  opposite  side,  dividing  the  integument,  superficial, 
and  deep  fascia.  The  operator  then  separates  the  two  sterno-thyroid 
muscles,  and,  following  the  course  of  the  trachea,  reaches  that  artery  as 


164 


THE   DISSECTOR. 


it  crosses  that  tube  to  the  right  side.  In  the  injected  subject  the  stu- 
dent will  find  this  by  no  means  a  difficult  operation :  the  artery  is  much 
more  superficial  than  might  be  expected,  and  the  practice  of  the  opera- 
tion on  the  subject  will  not  only  familiarize  him  with  the  natural  posi- 
tion of  the  artery,  but  also  with  the  proximity  of  the  arch  of  the  aorta, 
and  the  possibility  of  aneurism  of  that  vessel  making  its  appearance 
above  the  sternum.  The  inferior  thyroid  veins  are  very  much  in  the 
way  of  this  operation,  and  care  must  be  taken  not  to  wound  them.  An 
inferior  thyroid  artery,  from  the  innominata,  is  also  occasionally  met 
with.  The  layers  to  be  cut  through  are  simply  the  integument,  and 
superficial  and  deep  fascia. 

The  INTERNAL  JUGULAR  VEIN,  larger  than  the  common  carotid 
artery,  is  the  great  venous  trunk  by  which  the  blood  from  the 

Fig.  49. 


ANATOMY  OF  THE  NECK. — a.  The  anterior  bellies  of  the  digastric  muscles; 
their  tendinous  pulleys  are  seen  to  be  attached  to  the  os  hyoides,  b.  c.  The 
mylo-hyoideus  muscle,  on  which  is  seen  the  submental  branch  of  the  facial 
artery,  d.  The  hyo-glossus  muscle ;  the  artery  above  the  letter  is  the  facial  ; 
the  nerve  below  it,  the  hypoglossal ;  the  dotted  lines  below  the  nerve  indicate 
the  course  of  the  lingual  artery  behind  the  muscle,  e.  The  stylo-glossus  mus- 
cle, f.  The  styloid  process  and  muscles  proceeding  therefrom ;  the  white  band 
above /is  the  stylo-maxillary  ligament.  The  artery  in  front  of'/ is  the  external 
carotid ;  that  behind  it  is  the  posterior  auricular ;  the  large  nerve  crossing 


INTERNAL  JUGULAR  VEIN.  165 

these  arteries  is  the  facial,  g.  The  bifurcation  of  the  external  carotid  artery 
into  the  temporal  and  internal  maxillary,  h.  The  posterior  auricular  branch 
of  the  facial  nerve,  and  posterior  auricular  artery,  i  rests  on  the  middle  con- 
strictor and  stylo-pharyngeus  muscle ;  the  latter  is  crossed  by  the  glosso-pha- 
ryngeal  nerve,  which  is  seen  just  above  i.  The  large  artery  in  front  of  i  is 
the  external  carotid ;  the  artery  behind  it  the  occipital,  and  the  large  nerve 
below  it  the  hypoglossal.  It.  The  mastoid  branch  of  the  external  carotid.  The 
small  nerve  seen  in  the  space  above  this  branch  is  the  superior  laryngeal ;  and 
the  smaller  nerve  descending  behind  it,  upon  the  carotid  artery,  the  descendens 
noni.  /.  The  superior  thyroid  artery ;  just  below  the  letter,  the  common 
carotid  bifurcates  into  the  external  and  internal  carotid,  m.  The  thyro- 
hyoidean  membrane,  on  which  are  seen  the  superior  laryngeal  nerve  and  artery 
below,  and  the  hyoidean  branch  of  the  superior  thyroid  above  the  letter. 
n.  The  thyro-hyoid  muscle,  o,  o.  The  sterno -thyroid,  p.  The  thyroid  gland. 
q,  q.  Omo-hyoid  muscle,  r,  r.  The  sterno-hyoid  muscles,  s.  The  left  sterno- 
mastoid  muscle,  t.  The  origin  of  the  right  sterno-mastoid  muscle,  v.  The 
superior  obliquus  capitis  muscle ;  the  artery  meandering  over  this  muscle  is  the 
occipital ;  the  nerve  to  its  right  is  the  spinal  accessory,  w.  The  complexus 
muscle ;  the  small  artery  crossing  it  from  the  occipital,  is  the  princeps  cervicis. 
•x.  The  splenius  capitis.  y,  y.  The  levator  anguli  scapulae  muscle,  z.  The 
scalenus  posticus.  1.  The  scalenus  medius.  2.  The  scalenus  anticus.  The 
two  arteries  crossing  this  muscle  are  the  suprascapular  (the  lower)  and  trans- 
viT.-.'ilis  colli  (the  upper)  ;  the  trunk  from  which  they  proceed  is  the  thyroid 
axis,  which  is  also  seen  giving  off  the  inferior  thyroid  artery ;  the  latter,  after 
crossing  behind  the  common  carotid  artery,  3,  enters  the  lower  part  of  the  thy- 
roid gland,  p.  4,  4.  The  subclavian  artery.  The  large  artery  between  the 
thyroid  axis  and  common  carotid  is  the  vertebral,  and  the  nerves  crossing  the 
subclavian  in  this  situation,  the  pneumogastric  (the  larger)  and  a  branch  of 
the  sympathetic.  The  artery  proceeding  from  the  subclavian  below  the  thyroid 
axis,  is  the  internal  mammary,  and  the  nerve  near  it,  and  lying  on  the  scalenus 
anticus  (2),  is  the  phrenic.  5.  The  brachial  plexus  of  nerves.  6,  7.  The  in- 
ternal jugular  vein.  The  portion  6  accompanies  the  internal  carotid  artery; 
the  portion  7  the  common  carotid.  The  opening  just  below  6  is  the  divided 
trunk  of  the  facial  vein ;  the  slender  nerve  to  the  right  of  6  is  the  descendens 
noni ;  the  slender  nerve  to  the  left,  which  descends  to  join  the  descendens  noni, 
is  the  communicating  branch.  The  short  trunk  to  the  left  of  6  is  the  second 
cervical  nerve;  the  third  and  fourth  cervical  nerves  are  seen  lower  down,  and 
the  cervical  plexus  resting  on  the  levator  anguli  scapulae  and  scalenus  posticus 
muscle,  y,  y,  z.  The  little  artery  to  the  left  of  the  internal  jugular  vein,  7,  is 
the  cervicalis  ascendens  branch  of  the  inferior  thyroid.  8.  The  inferior  con- 
strictor muscle ;  the  figure  is  placed  between  the  trunk  of  the  superior  thyroid 
artery,  and  its  muscular  branch.  9.  The  oesophagus;  the  artery  immediately 
above  the  figure  is  the  inferior  thyroid.  10.  The  trapezius  muscle.  11.  The 
deltoid.  12.  The  clavicular  portion  of  the  pectoralis  major.  13.  Its  sternal 
portion.  14.  The  subclavius  muscle.  15.  The  axillary  artery,  giving  off  the 
thoracico-acromialis  artery. 

sinuses  of  the  cranium  reaches  the  heart.  It  commences  at  the 
jugular  foramen  in  the  base  of  the  skull,  and,  passing  down  the 
front  of  the  vertebral  column,  becomes  inclosed  in  the  sheath  of 
the  common  carotid  artery  lying  to  the  outer  side  and  parallel 
with  that  vessel.  At  the  root  of  the  neck,  on  the  right  side,  the 
vein  diverges  from  the  artery,  and  a  triangular  space  is  formed 
between  them,  through  which  the  pneumogastric  nerve  may  be 
seen ;  on  the  left  side  no  such  separation  exists.  The  internal 
jugular  vein  unites  with  the  subclavian  vein  to  form  the  vena 
innominata. 


166  THE   DISSECTOR. 

The  branches  which  the  internal  jugular  vein  receives,  while 
situated  in  the  carotid  sheath,  are  the  superior  and  middle  thy- 
roid veins. 

Lymphatic  Glands  and  Vessels. — The  deep  lymphatic  glands 
and  vessels  of  the  neck  are  situated  along  the  course  of  the  in- 
ternal jugular  vein,  chiefly  on  its  outer  side,  while  a  few  are 
found  by  the  side  of  the  pharynx,  esophagus,  and  trachea.  The 
lymphatic  vessels  terminate,  on  the  right  side,  in  the  ductus 
lymphaticus  dexter,  and  on  the  left  in  the  thoracic  duct. 

The  ductus  lymphaticus  dexter  is  a  short  trunk  formed  by  the 
union  of  the  lymphatic  vessels  of  the  right  side  of  the  head, 
right  upper  extremity,  and  right  side  of  the  thorax.  It  is  situated 
at  the  root  of  the  neck  on  the  right  side,  and  terminates  at  the 
point  of  junction  of  the  internal  jugular  with  the  subclavian  vein, 
on  the  posterior  aspect  of  the  vessel.  At  its  termination  it  is 
provided  with  a  pair  of  semilunar  valves. 

The  thoracic  duct  ascends  into  the  left  side  of  the  root  of 
the  neck,  behind  the  first  portion  of  the  subclavian  artery,  as 
high  as  the  last  cervical  vertebra.  It  then  curves  downwards 
and  forwards  in  front  of  the  scalenus  anticus  and  phrenic  nerve, 
and  terminates  by  opening  into  the  posterior  aspect  of  the  junc- 
tion of  the  internal  jugular  and  subclavian  vein.  In  the  root  of 
the  neck  it  receives  the  lymphatics  of  the  left  side  of  the  head 
and  neck,  left  upper  extremity,  and  left  half  of  the  thorax.  At 
its  opening  into  the  vein,  the  thoracic  duct  is  provided  with  a 
pair  of  semilunar  valves. 

The  student  should  now  proceed  to  dissect  the  external  carotid  artery 
and  its  branches,  taking  care  not  to  divide  the  nerves  which  cross  it 
in  its  course. 

The  EXTERNAL  CAROTID  ARTERY  ascends  nearly  perpendicularly 
from  a  point  opposite  the  upper  border  of  the  thyroid  cartilage 
to  the  space  between  the  neck  of  the  lower  jaw  and  meatus  audi- 
torius,  where  it  divides  into  two  terminal  branches,  the  temporal 
and  internal  maxillary. 

In  the  beginning  of  its  course  it  is  superficial,  being  covered 
in  only  by  the  platysma  and  deep  fascia,  and  crossed  by  the 
hypoglossal  nerve;  a  little  higher  it  is  crossed  by  the  digas- 
tricus  and  stylo-hyoid  muscle;  and  higher  still  it  enters  the  sub- 
stance of  the  parotid  gland,  and  has  in  front  of  it  the  facial 
nerve  and  temporo-maxillary  vein.  Crossing  behind  it,  and 
separating  it  from  the  internal  carotid,  is  the  stylo-pharyngeus 
and  stylo-glossus  muscle,  the  glosso-pharyngeal  nerve,  and  the 
deep  part  of  the  parotid  gland.  The  internal  carotid  artery  lies 
at  first  to  the  outer  side  of  the  external  carotid,  but  soon  gets 
behind  it. 

The  branches  of  the  external  carotid  (ten  in  number)  are  divided 


LINGUAL  ARTERY.  167 

into  three  sets — anterior,  posterior,  and  ascending.     They  are  as 
follows  : — 

Anterior.  Posterior. 

Superior  thyroid,  Sterno-mastoid, 

Lingual,  Occipital, 

Facial.  Posterior  auricular. 

Ascending. 

Ascending  pharyngeal, 
Parotidean, 
Temporal, 
Internal  maxillary. 

1.  The  SUPERIOR  THYROID  ARTERY,  the  first  of  the  branches  of  the 
external  carotid,  arises  from  that  trunk  just  below  the  great  cornu 
of  the  os  hyoides,  and  curves  downwards  to  the  thyroid  gland. 
It  is  distributed  by  several  large  branches  to  the  anterior  part  of 
the  gland,  and  anastomoses  with  its  fellow  of  the  opposite  side, 
and  with  the  inferior  thyroid  arteries.  In  its  course  it  passes 
beneath  the  omo-hyoid,  sterno-thyroid,  and  sterno-hyoid  muscles. 
The  branches  of  the  superior  thyroid  artery  are  the 

Hyoid,  Inferior  laryngeal, 

Superior  laryngeal,  Muscular. 

The  hyoid  branch  passes  forwards  beneath  the  thyro-hyoideus, 
and  is  distributed  to  the  depressor  muscles  of  the  os  hyoides  near 
their  insertion. 

The  superior  laryngeal  pierces  the  thyro-hyoidean  membrane, 
in  company  with  the  superior  laryngeal  nerve,  and  supplies  the 
mucous  membrane  and  muscles  of  the  larynx,  sending  a  branch 
upwards  to  the  epiglottis. 

The  inferior  laryngeal  (crico-thyroid)  is  a  small  branch  which 
crosses  the  crico-thyroidean  membrane  near  the  lower  border  of 
the  thyroid  cartilage.  It  sends  branches  through  that  membrane 
to  supply  the  mucous  lining  of  the  larynx,  and  inosculates  with 
its  fellow  of  the  opposite  side. 

The  muscular  branches  are  distributed  to  the  depressor  muscles 
of  the  os  hyoides  and  larynx.  One  of  these  branches  crosses  the 
sheath  of  the  common  carotid  to  the  under  surface  of  the  sterno- 
mastoid  muscle. 

The  LINGUAL  ARTERY  arises  just  above  the  superior  thyroid, 
and,  bending  upwards  over  the  gi€bt  cornu  of  the  os  hyoides, 
runs  forward  nearly  parallel  with  that  bone ;  it  then  ascends  to 
the  under  surface  of  the  tongue,  and  passes  onwards,  in  a  ser- 
pentine course,  to  the  tip  of  the  organ,  under  the  name  of  ranine 
artery. 

The  first  portion  of  the  artery  is  superficial,  although  crossed 


168 


THE  DISSECTOR. 


by  the  digastricus  and  stylo-hyoid  muscle,  and  by  the  hypoglossal 
nerve.  In  its  horizontal  and  oblique  course  it  lies  beneath  the 

Fig.  50.  THE  ANATOMY  OF  THE  SIDE 

OF  THE  TONGUE,  WITH  THE 
RELATIONS  OF  THE  VESSELS 
AND  NEKVES. — 1.  The  hyo- 
glossus  muscle,  arising  from  the 
side  of  the  os  hyoides  below,  and 
inserted  into  the  side  of  the 
tongue,  where  it  mingles  its 
fibres  with  those  of  the  stylo- 
glossus  muscle.  2,3.  A  section 
of  the  lower  jaw  at  the  symphy- 
sis.  4.  The  genio-hyo-glossus 
muscle.  5.  The  genio-hyoideus 
muscle.  6.  The  cut  edge  of  the 
mylo-hyoideus.  7.  The  com- 
mon carotid  artery,  dividing 
into  the  external  and  internal 
carotid.  8.  The  trunk  of  the 
superior  thyroid  artery.  9.  The 
lingual  artery ;  the  first,  or 
oblique  portion  of  its  course, 
resting  upon  the  great  cornu  of 

the  os  hyoides,  and  upon  (10)  the  middle  constrictor  muscle.  11.  The  second, 
or  horizontal  portion  of  the  lingual  artery  ;  its  course  beneath  the  hyo-glossus 
muscle  is  marked  by  dotted  lines.  12.  The  third,  or  perpendicular  portion  of 
the  lingual  artery.  13.  Its  termination,  the  ranine  artery.  14.  The  trunk  of 
the  facial  artery.  15.  The  three  posterior  branches  of  the  external  carotid  ar- 
tery ;  they  are  from  below,  upwards,  the  mastoid,  occipital,  and  posterior  auri- 
cular. 16.  The  trunk  of  the  ascending  pharyngeal  artery.  17.  The  trunk  of 
the  transverse  facial  artery.  18.  The  two  terminal  branches  of  the  external 
carotid,  the  internal  maxillary  and  temporal.  19.  The  gustatory  branch  of  the 
fifth  nerve.  *  Its  communication  with  the  lingual  nerve.  20.  The  glosso-pha- 
ryngeal  nerve.  21.  The  lingual,  or  hypoglossal  nerve.  22.  Wharton's  duct. 
23.  The  sublingual  gland. 

hyo-glossus,  being  at  first  placed  between  that  muscle  and  the 
middle  constrictor,  and  then  between  it  and  the  genio-hyo- 
glossus.  In  its  course  along  the  under  surface  of  the  tongue,  it 
lies  between  the  lingualis  and  mucous  membrane.  The  hyo- 
glossus  muscle  separates  it  from  the  hypoglossal  nerve. 

Operation. — The  lingual  artery  is  tied  in  the  upper  angle  of  the  supe- 
rior carotid  triangle.  The  external  incision  should  be  made  parallel  with 
the  lower  border  of  the  posterior  belly  of  the  digastricus  muscle.  It 
should  cut  through  the  integument,  superficial  fascia,  platysma,  and 
deep  fascia.  The  hyo-glossus  will  then  form  the  floor  of  the  wound,  upon 
which  rests  the  lingual  nerve ;  this  must  be  carefully  avoided  by  making 
the  incision  through  the  musclebelow  the  nerve.  The  artery  will  then 
be  exposed  in  the  second  part  oyits  course. 

The  structures  to  be  cut  through  are  the  integument,  superficial  fascia, 
platysma,  superjicialis  colli  nerve,  deep  fascia,  and  hyo-glossus  muscle. 

The  branches  of  the  lingual  artery  are  the 
Hyoid, 

Dorsalis  linguae, 
Sublingual. 


FACIAL  ARTERY.  169 

The  hyoid  branch  runs  along  the  upper  border  of  the  os 
hyoides,  and  is  distributed  to  the  elevator  muscles  of  the  os 
hyoides,  near  their  origin,  inosculating  with  its  fellow  of  the  op- 
posite side. 

The  dorsalis  linguae  ascends  along  the  posterior  border  of  the 
hyo-glossus  muscle,  to  the  dorsum  of  the  tongue,  and  is  distri- 
buted to  the  tongue,  the  fauces,  and  epiglottis,  anastomosing 
with  its  fellow  of  the  opposite  side. 

The  sublingual  branch  runs  forwards  on  the  genio-hyo-glossus 
muscle,  and  is  distributed  to  the  sublingual  gland  and  to  the 
muscles  of  the  tongue.  It  is  situated  between  the  mylo-hyoideus 
and  genio-hyo-glossus,  generally  accompanies  Wharton's  duct 
for  a  part  of  its  course,  and  sends  a  branch  to  the  fraenum 
linguae.  It  is  the  latter  branch  which  affords  the  considerable 
hemorrhage  which  sometimes  follows  the  operation  of  snipping 
the  fraenum  in  children. 

The  ranine  artery  (the  continuation  of  the  lingual  beyond  the 
origin  of  the  sublingual),  terminates  at  the  tip  of  the  tongue  by 
inosculating  with  its  fellow  of  the  opposite  side. 

The  FACIAL  ARTERY  arises  immediately  above  the  lingual  and 
a  little  above  the  great  cornu  of  the  os  hyoides,  and  passes  for- 
wards to  the  submaxillary  gland,  in  which  it  lies  embedded.  It 
then  curves  around  the  body  of  the  lower  jaw,  close  to  the  an- 
terior inferior  angle  of  the  masseter  muscle,  ascends  to  the  angle 
of  the  mouth,  and  thence  to  the  angle  of  the  eye,  where  it  is 
named  the  angular  artery. 

In  its  course  to  the  lower  jaw  it  is  crossed  by  the  digastricus 
and  stylo-hyoid  muscle,  and  then  becomes  lodged  in  the  submax- 
illary gland,  wherein  it  makes  a  considerable  bend.  Its  course 
and  relations  on  the  face  have  been  already  described  (p.  127). 

Operation. — The  facial  artery  is  usually  tied  while  resting  on  the  body 
of  the  lower  jaw,  close  to  the  anterior  inferior  angle  of  the  masseter 
muscle.  It  is  here  superficial,  and  may  be  felt  and  seen  pulsating  im- 
mediately beneath  the  integument.  It  is  covered  by  the  integument, 
superficial  fascia,  and  platysma.  If  it  were  necessary  to  tie  the  artery 
below  the  jaw,  the  upper  border  of  the  posterior  belly  of  the  digastric 
muscle  would  be  the  guide  to  the  vessel.  The  ligature  might  then  be 
passed  around  it  just  before  it  entered  the  submaxillary  gland,  whilst 
resting  against  the  stylo-maxillary  ligament.  The  structures  to  be  cut 
through  are  the  integument,  superficial  fascia,  platysma,  cervical  branches 
of  the  facial  nerve,  and  deep  fascia. 

The  branches  of  the  facial  artery  below  the  lower  jaw  are,  the— 
Inferior  palatine,  Submaxillary, 

Tonsillar,  Submeutal. 

The  inferior  palatine  branch  ascends  between  the  stylo-glossus 
and  stylo-pharyng'eus  muscle,  to  be  distributed  to  the  tonsil  and 
15 


170  THE  DISSECTOR. 

soft  palate,  and  anastomoses  with  the  posterior  palatine  branch 
of  the  internal  maxillary  artery. 

The  tonsillar  branch  ascends  upon  the  side  of  the  pharynx, 
and  pierces  the  superior  constrictor  muscle,  to  be  distributed  to 
the  tonsil. 

The  submaxillary  (glandular)  are  four  or  five  branches  which 
supply  the  submaxillary  gland. 

T he  submental  branch  runs  forward  upon  the  mylo-hyoid  muscle, 
under  cover  of  the  body  of  the  lower  jaw,  and  anastomoses  with 
branches  of  the  sublingual  and  inferior  dental  artery. 

The  STERNO-MASTOID  ARTERY  turns  downwards  from  its  origin, 
to  be  distributed  to  the  sterno-mastoid  muscle  and  lymphatic 
glands  of  the  neck.  Sometimes  there  are  two  branches. 

The  OCCIPITAL  ARTERY,  smaller  than  the  anterior  branches, 
passes  backwards  behind  the  parotid  gland  and  beneath  the  pos- 
terior belly  of  the  digastricus,  trachelo-mastoid,  and  sterno-mas- 
toid muscle,  to  the  occipital  groove  in  the  mastoid  portion  of 
the  temporal  bone.  It  then  ascends  between  the  splenius  and 
cornplexus,  pierces  the  trapezius,  and  is  distributed  to  the  back 
of  the  head  (p.  116).  Opposite  the  angle  of  the  jaw,  the  hypo- 
glossal  nerve  curves  forward  around  the  artery. 

Besides  muscular  branches  to  the  muscles  near  which  it  passes, 
the  occipital  artery  gives  off  but  one  named  artery  in  the  front 
of  the  neck  ;  namely,  the  inferior  meningeal,  which  ascends  by 
the  side  of  the  internal  jugular  vein,  and  passes  through  the 
foramen  lacerum  posterius  to  be  distributed  to  the  dura  mater. 

The  POSTERIOR  AURICULAR  ARTERY  arises  from  the  external 
carotid,  above  the  level  of  the  digastric  and  stylo-hyoid  muscles, 
and  ascends  by  the  side  of  the  styloid  process,  and  behind  the 
parotid  gland,  to  the  back  part  of  the  concha.  It  is  distributed 
by  two  branches  to  the  external  ear  and  side  of  the  head,  anasto- 
mosing with  the  occipital  and  temporal  arteries ;  some  of  its 
branches  pass  through  fissures  in  the  fibro-cartilage,  to  reach  the 
anterior  surface  of  the  pinna.  The  anterior  auricular  arteries  are 
branches  of  the  temporal. 

The  posterior  auricular  sends  a  branch  to  the  digastricus  mus- 
cle, and  several  to  the  parotid  gland  ;  it  then  gives  off  the  stylo- 
mastoid,  which  enters  the  stylo-mastoid  foramen,  to  be  distributed 
to  the  aquaeductus  Fallopii,  labyrinth,  mastoid  cells,  and  tympa- 
num. 

The  ASCENDING  PHARYNGEAL  ARTERY,  the  smallest  of  the 
branches  of  the  external  carotid,  arises  from  that  trunk  near  its 
bifurcation,  and  ascends  between  the  internal  carotid  and  the 
side  of  the  pharynx  to  the  base  of  the  skull,  where  it  divides  into 
two  branches — meningeal,  which  enters  the  foramen  lacerum  pos- 


TEMPORAL   ARTERY.  171 

terms,  to  be  distributed  to  the  dura  mater,  and  pharyngeal.     It 
supplies  the  pharynx,  tonsils,  soft  palate,  and  Eustachian  tube. 

The '  PAROTIDEAN  ARTERIES  are  four  or  five  large  branches 
which  are  given  off  from  the  external  carotid  whilst  that  vessel 
is  situated  in  the  parotid  gland.  They  are  distributed  to  the 
structure  of  the  gland,  their  terminal  branches  reaching  the  in- 
tegument of  the  side  of  the  face. 

The  TEMPORAL  ARTERY  is  one  of  the  two  terminal  branches  of 
the  external  carotid.  It  ascends  over  the  root  of  the  zygoma, 
and,  at  about  an  inch  and  a  half  above  the  zygomatic  arch, 
divides  into  an  anterior  and  a  posterior  temporal  branch.  The 
anterior  temporal  is  distributed  over  the  front  of  the  temple  and 
arch  of  the  skull,  and  anastomoses  with  the  opposite  anterior 
temporal  and  with  the  supraorbital  and  frontal  artery.  The 
posterior  temporal  curves  upwards  and  backwards,  and  inoscu- 
lates with  its  fellow  of  the  opposite  side,  with  the  posterior 
auricular  and  occipital  artery. 

The  trunk  of  the  temporal  artery  is  covered  by  the  parotid 
gland  and  by  the  attrahens  aureni  muscle,  and  rests  on  the  tem- 
poral fascia. 

The  branches  of  the  temporal  artery  are  :  some  small  offsets  to 
the  parotid  gland,  articulation  of  the  lower  jaw,  external  ear  and 
orbit ;  and  two  of  larger  size — the  transverse  facial  and  middle 
temporal. 

The  branches  to  the  external  ear  (anterior  auricular)  are  two 
in  number,  and  are  distributed  to  the  anterior  portion  of  the 
pinna. 

The  branch  to  the  orbit  (orbitar)  passes  forward,  immediately 
above  the  zygoma,  between  the  two  layers  of  the  temporal  fascia, 
and  inosculates  beneath  the  orbicularis  with  a  branch  of  the 
lachrymal  artery. 

The  transversalis  faciei  arises  from  the  temporal  immediately 
below  the  zygoma,  and  runs  transversely  across  the  face,  resting 
on  the  masseter  muscle,  and  lying  parallel  with  and  a  little  above 
Stenon's  duct.  It  anastomoses  with  the  facial  and  infra-orbital 
artery. 

The  middle  temporal  branch  passes  through  an  opening  in  the 
temporal  fascia  immediately  above  the  zygoma,  and  supplies  the 
temporal  muscle,  inosculating  with  the  deep  temporal  arteries. 

The  examination  of  the  next  artery,  the  internal  maxillary,  requires 
the  preparation  already  described  (page  124)  for  the  study  of  the  pterygoid 
muscles.  The  temporal  fascia  should  be  divided  along  the  upper  border 
of  thf  zygoma  ;  the  zygoma  cut  through  with  the  saw  at  both  ends,  and 
turned  down  with  the  masseter  muscle  ;  noting  in  this  part  of  the  dis- 
section the  masseteric  artery  and  nerve,  which  cross  the  sigmoid  notch  of 


THE   DISSECTOR. 


the  lower  jaw,  to  enter  the  under  surface  of  that  muscle.  The  coronoid 
process  of  the  lower  jaw  should  then  be  sawn  through,  and  drawn  upwards 
with  the  temporal  muscle.  Next  the  neck  of  the  lower  jaw  should  be 
cut  across  ;  and  then  the  ramus,  down  to  the  dental  foramen.  The  fat 
and  cellular  tissue  may  then  be  cleared  away,  carefully  preserving  any 
branches  of  nerves,  and  the  internal  maxillary  artery  and  such  of  its 
branches  as  are  visible  at  this  stage  of  the  dissection  may  be  followed  in 
their  course. 

The  INTERNAL  MAXILLARY  ARTERY,  one  of  the  terminal  branches 
of  the  external  carotid,  commences  in  the  substance  of  the  parotid 
gland  opposite  the  meatus  auditorius.  It  passes  forwards  behind 
the  neck  of  the  lower  jaw,  curves  around  the  lower  border  of  the 
external  pterygoid  muscle,  and  ascends  obliquely  forwards  upon 
the  outer  aspect  of  that  muscle  to  the  space  between  its  two  heads. 
It  then  passes  horizontally  inwards  between  the  two  heads  of  the 
external  pterygoid,  and  enters  the  spheno-maxillary  fossa,  where 
it  divides  into  its  terminal  branches. 

The  artery  admits  of  a  natural  division  into  three  parts  ;  first, 
that  situated  behind  the  neck  of  the  lower  jaw,  maxillary  portion  ; 
second,  that  in  relation  with  the  external  pterygoid  muscle, 
pterygoid  portion;  third,  that  situated  in  the  spheno-maxillary 
fossa,  spheno-maxillary  portion. 

The  maxillary  portion  is  situated  between  the  neck  of  the  jaw 
and  the  internal  lateral  ligament  and  inferior  dental  nerve,  and 
lies  parallel  with  the  auriculo-temporal  nerve.  The  pterygoid 

Fig.  51.  THE  INTERNAL  MAXILLARY  AR- 

TERY, WITH  ITS  BRANCHES. — 1.  The 
external  carotid  artery.  2.  The  trunk 
of  the  transverse  facial  artery.  3,  4. 
The  two  terminal  branches  of  the 
external  carotid.  3.  The  temporal 
artery  ;  and  4.  The  internal  maxil- 
lary, the  first  or  maxillary  portion 
of  its  course:  the  limit  of  this  portion 
is  marked  by  an  arrow.  5.  The 
second,  or  muscular  portion,  of  the 
artery  ;  the  limits  are  bounded  by  the 
arrows.  6.  The  third,  or  ptery go- 
maxilla  ry  portion.  The  branches  of 
the  maxillary  portion  are,  7.  A  tym- 
panic branch.  8.  The  arteria  me- 
ningea  media.  9.  The  arteria  me- 
ningeaparva.  10.  The  inferior  dental 
artery.  The  branches  of  the  second 
portion  are  wholly  muscular,  the  as- 
cending ones  being  distributed  to  the 

temporal,  and  the  descending  to  the  four  other  muscles  of  the  inter-maxillary 
region,  viz:  the  two  pterygoids,  the  masseter  and  buccinator.  The  branches  of 
the  pterygo-maxillary  portion  of  the  artery  are,  11.  The  superior  dental  artery. 
12.  The  infra-orbital  artery.  13.  The  posterior  palatine.  14.  The  spheno- 
palatine,  or  nasal.  15.  The  pterygo-palatine.  16.  The  Vidian.  *  The  re- 
markable bend  which  the  third  portion  of  the  artery  makes  as  it  turns  inwards 
to  enter  the  pterygo-maxillary  fossa. 


INTERNAL  MAXILLARY  ARTERY.  173 

portion  lies  between  the  external  pterygoid  and  the  masseter  and 
temporal  muscle,  and  is  crossed  by  the  masseteric  nerve. 

Having  thus  far  examined  the  internal  maxillary  artery  and  its  rela- 
tions, the  head  of  the  lower  jaw  should  be  dislocated  and  drawn  forwards 
with  the  external  pterygoid  muscle,  in  order  to  be  able  to  dissect  the 
branches  of  the  artery  which  lie  behind.  Before  disturbing  the  muscle, 
however,  the  student  should  observe  the  nerves  and  vessels  which  are 
in  relation  with  it.  At  its  upper  border  he  will  find  the  temporal  nerve, 
the  deep  temporal  arteries,  and  the  masseteric  nerve.  Piercing  the 
muscle  at  its  anterior  part  is  the  buccal  nerve.  Lying  against  the  su- 
perior maxillary  bone,  just  in  front  of  its  attachment,  is  the  superior 
dental  nerve,  accompanied  by  its  artery.  Issuing  from  below  the  muscle 
are  two  large  nerves,  the  gustatory  and  inferior  dental ;  and,  passing 
backwards  behind  its  condyloid  attachment,  is  the  auriculo-temporal 
nerve. 

When  the  external  pterygoid  muscle  is  drawn  forwards,  these  nerves 
may  be  traced  to  their  origin  from  the  inferior  maxillary  nerve  ;  they 
should  be  cleared  of  fat  and  cellular  tissue,  as  well  as  the  arterial  branches 
of  the  internal  maxillary.  Numerous  veins,  part  of  a  plexus,  will  be  found 
between  the  two  pterygoid  muscles ;  these  must  be  removed.  The  auriculo- 
temporal  nerve  may  then  be  followed  in  its  course  backward,  and  a  small 
nerve  observed,  the  chorda  tympani,  which  joins  the  gustatory  nerve  at 
an  acute  angle  on  the  internal  pterygoid  muscle. 

The  branches  of  the  internal  maxillary  artery,  grouped  into 
three  sets  in  correspondence  with  the  divisions  of  the  trunk  of 
the  artery,  are  as  follows  : — 

Maxillary  portion.  Pterygoid  portion. 

Tympanic,  Deep  temporal, 

Inferior  dental,  Pterygoid, 

Arteria  meningea  media,  Masseteric, 

Artcria  meningea  parva.  Buccal. 

Pterygo-maxillary  portion. 
Superior  dental, 
Infra-orbital, 
Ptery  go-palati  ne, 
Spheno-palatine, 

Descending  or  posterior  palatine, 
Vidian. 

The  tympanic  branch  passes  into  the  tympanum  through  the 
fissura  Glaseri,  and  is  distributed  to  the  laxator  tyrapaui  and 
membrana  tympani ;  on  the  latter,  it  inosculates  with  the  stylo- 
mast  old  artery. 

The  inferior  dental  descends  to  the  dental  foramen,  and  enters 
the  canal  of  the  lower  jaw  in  company  with  the  dental  nerve. 
Opposite  the  bicuspid  teeth,  it  divides  into  two  branches,  one  of 
which  is  continued  onwards  within  the  bone  as  far  as  the  sym- 
physis  to  supply  the  incisor  teeth,  while  the  other  escapes  with 

15* 


174  THE   DISSECTOR. 

the  nerve  at  the  mental  foramen,  and  anastomoses  with  the  infe- 
rior labial  and  submental  branch  of  the  facial.  It  supplies  the 
teeth  of  the  lower  jaw,  sending  small  branches  along  the  canals 
in  their  roots  ;  at  the  inferior  dental  foramen,  it  gives  off  a  mylo- 
hyoid  branch,  which  accompanies  the  mylo-hyoidean  nerve. 

The  arteria  meningea  media  ascends  behind  the  temporo- 
maxillary  articulation  to  the  foramen  spinosum  in  the  spinous 
process  of  the  sphenoid  bone,  and,  entering  the  cranium,  divides 
into  an  anterior  and  a  posterior  branch,  which  are  distributed  to 
the  dura  mater  and  bone. 

The  meningea  parva  is  a  small  branch  which  ascends  to  the 
foramen  ovale,  and  passes  into  the  skull,  to  be  distributed  to  the 
Casserian  ganglion  and  dura  mater ;  it  gives  off  a  twig  to  the 
nasal  fossae  and  soft  palate. 

The  muscular  branches  are  distributed,  as  their  names  imply, 
to  the  five  muscles  of  the  maxillary  region.  The  temporal  branches 
(ternporales  profundae)  are  two  in  number  ;  they  inosculate  with 
branches  of  the  superficial  temporal.  The  pterygoid  branches  are 
distributed  to  both  the  muscles  of  that  name.  The  masseteric 
artery  passes  outwards,  behind  the  tendon  of  the  temporal  mus- 
cle, and  over  the  sigmoid  notch,  to  the  masseteric  muscle.  The 
buccal  branch,  arising  over  the  anterior  part  of  the  pterygoid 
muscle,  passes  downwards  with  the  buccal  nerve  to  the  buccinator 
muscle ;  it  inosculates  with  the  facial  and  transverse  facial  artery. 
The  superior  dental  artery  (alveolar,  superior  maxillary)  is 
given  off  from  the  internal  maxillary  just  as  that  vessel  is  about 
to  make  its  turn  inwards  to  reach  the  spheno-maxillary  fossa  ; 
it  descends  upon  the  tuberosity  of  the  superior  maxillary  bone, 
and  sends  its  branches  through  several  small  foramina  to  supply 
the  posterior  teeth  of  the  upper  jaw  and  the  antrum.  The  termi- 
nal branches  are  continued  forwards  upon  the  alveolar  process, 
to  be  distributed  to  the  gums  and  sockets  of  the  teeth. 

To  see  the  remaining  brandies  of  the  internal  maxillary  artery,  the 
outer  wall  of  the  orbit  must  be  divided  with  the  saw  to  the  level  of  the 
cheek,  and  removed. 

The  saw  should  then  be  carried  through  the  great  ala  of  the  sphenoid 
bone,  the  dura  mater  having  been  stripped  from  its  surface,  to  the  fora- 
men rotundum  ;  another  section  must  be  made  through  the  squamous 
portion  of  the  temporal  bone  to  the  foramen  spinosum,  and  the  extremities 
of  the  sections  connected  by  means  of  the  chisel.  The  piece  of  bone 
included  by  these  incisions  is  then  to  be  broken  outwards,  and  any  pieces 
of  bone  remqved  which  may  interfere  with  the  view  of  the  inferior  and 
superior  maxillary  nerves,  passing  through  their  respective  openings  and 
spheno-maxillary  fossa.  For  the  present,  the  student  must  be  satisfied 
with  tracing  the  branches  as  far  as  the  openings  through  which  they  pass, 
and  not  attempt  to  follow  them  in  their  course  ;  he  should  also  disturb 
the  neighboring  parts  as  little  as  possible,  in  order  to  aypid  injury  to 
Meckel's  ganglion  and  its  branches. 


VEINS   OP  THE   EXTERNAL  CAROTID.  175 

The  infra-orbital  artery  would  appear  from  its  size  to  be  the 
proper  continuation  of  the  internal  maxillary.  It  runs  along  the 
infra-orbital  canal  with  the  superior  maxillary  nerve,  sending 
branches  upwards  into  the  orbit;  and  downwards,  through  canals 
in  the  bone,  to  supply  the  mucous  membrane  of  the  antrum,  and 
the  teeth  of  the  upper  jaw,  and  emerging  on  the  face  at  the  infra- 
orbital  foramen.  A  branch  sent  to  the  incisor  teeth  is  the  ante- 
rior dental;  and  on  the  face  the  infra-orbital  inosculates  with  the 
facial  and  transverse  facial  artery. 

The  ptery go-palatine  is  a  small  branch  which  passes  backwards 
through  the  pterygo-palatine  canal,  and  supplies  the  upper  part 
of  the  pharynx,  Eustachian  tube,  and  sphenoidal  cells. 

The  spheno-palatine,  or  nasal,  enters  the  superior  meatus  of 
the  nose  through  the  spheno-palatine  foramen  in  company  with 
the  nasal  branches  of  Meckel's  ganglion,  and  divides  into  two  or 
three  branches.  One  branch  (artery  of  the  septum),  is  distributed 
to  the  mucous  membrane  of  the  septum,  and  inosculates  in  the 
anterior  palatine  canal  with  a  terminal  branch  of  the  descending 
palatine.  Another  branch  supplies  the  mucous  membrane  of 
the  lateral  wall  of  the  nares,  antrum,  sphenoid  and  ethmoid 
cells. 

The  superior  or  descending  palatine  artery  (posterior  palatine), 
descends  along  the  posterior  palatine  canal,  in  company  with  the 
palatine  branches  of  Meckel's  ganglion,  to  the  posterior  pala- 
tine foramen.  It  then  bends  forward,  lying  in  a  groove  upon 
the  bone,  and  is  distributed  to  the  palate.  While  in  the  poste- 
rior palatine  canal  it  sends  a  branch  backwards,  through  the 
small  posterior  palatine  foramen,  to  supply  the  soft  palate,  and 
anteriorly  it  distributes  a  branch  to  the  anterior  palatine  canal, 
which  reaches  the  nares  and  inosculates  with  the  branches  of  the 
spheno-palatine  artery. 

The  Vidian  branch  passes  backwards  along  the  pterygoid 
canal,  and  is  distributed  to  the  sheath  of  the  Vidian  nerve,  and 
to  the  Eustachian  tube. 

VEINS  OF  THE  EXTERNAL  CAROTID. — The  veins  of  the  branches 
of  the  external  carotid  artery  follow  the  direction  of  their  re- 
spective vessels.  The  internal  maxillary  vein  commences  by  the 
union  of  veins  returning  the  blood  from  the  zygomatic  and  ptery- 
goid fossa,  where  they  are  so  numerous  and  communicate  so 
freely  with  each  other  as  to  constitute  a  pterygoid  plexus.  Be- 
hind the  neck  of  the  lower  jaw  the  internal  maxillary  vein  unites 
with  the  temporal  vein,  and  the  two  together  constitute  the  tem- 
poro-maxillary  vein.  The  temporo-maxillary  vein  descends 
through  the  substance  of  the  parotid  gland,  receiving  in  its 
course  the  transverse  facial,  anterior  auricular,  and  parotid  veins. 
At  the  lower  part  of  the  gland  it  is  joined  by  the  posterior  auri- 


116  THE   DISSECTOR. 

cular  vein,  and  becomes  the  external  jugular.  The  external 
jugular  vein  communicates  with  the  internal  jugular  in  the  pa- 
rotid gland,  and  after  receiving  a  cutaneous  branch  from  the 
occipital  region  takes  its  course  down  the  neck,  across  the  sterno- 
mastoid  muscle,  to  the  subclavian  vein. 

The  facial,  the  occipital,  the  lingual,  and  superior  thyroid  veins 
open  into  the  internal  jugular  vein. 

Fifth  Pair  of  Nerves. 

The  preparation  already  made  for  the  examination  of  the  internal 
maxillary  artery  and  its  branches,  is  that  which  is  best  suited  for  the 
display  of  the  two  maxillary  divisions  of  the  fifth  nerve,  superior  and 
inferior.  Within  the  cranium,  the  dura  mater  should  be  stripped  off 
the  bones  of  the  middle  fossa,  so  as  to  expose  the  Casserian  ganglion,  and 
the  ganglion  may  be  carefully  raised  from  its  bed  in  order  to  see  the  an- 
terior root  of  the  nerve,  in  its  course  beneath  the  ganglion  to  join  the 
inferior  maxillary  nerve.  In  the  present  dissection  it  will  be  more  con- 
venient to  study  the  inferior  maxillary  nerve  before  the  superior. 

The  FIFTH  NERVE  (trifacial ;  trigeminus),  is  the  great  sensitive 
nerve  of  the  head  and  face,  and  the  largest  of  the  cranial  nerves. 
It  is  a  flattened  cord,  composed  of  a  number  of  filaments  held 
together  by  a  sheath  of  the  arachnoid  membrane.  It  passes 
through  an  oval  opening  in  the  dura  mater,  near  the  extremity 
of  the  petrous  portion  of  the  temporal  bone,  resting  in  a  groove 
upon  that  bone,  and  spreads  out  into  a  large  flattened  semilunar 
ganglion — the  Casserian.  The  Casserian  ganglion  occupies  a  con- 
siderable extent  of  space  immediately  in  front  of  the  extremity 
of  the  petrous  bone,  and  upon  the  base  of  the  great  wing  of  the 
sphenoid,  and  divides  into  three  branches — ophthalmic,  superior 
maxillary,  and  inferior  maxillary. 

The  ophthalmic  nerve,  the  smallest  of  the  three,  is  about  three 
quarters  of  an  inch  in  length ;  it  is  situated  in  the  outer  wall  of 
the  cavernous  sinus,  externally  to  the  other  nerves  in  the  sinus, 
and  divides  into  three  branches — -frontal,  lachrymal,  and  nasal, 
which  enter  the  orbit  through  the  sphenoidal  fissure  (page  134). 

The  superior  maxillary  nerve  passes  forwards  to  the  foramen 
rotundum,  through  which  it  escapes  from  the  cranium. 

The  INFERIOR  MAXILLARY  NERVE,  the  largest  of  the  three, 
proceeds  from  the  posterior  angle  of  the  Casserian  ganglion,  and 
passes  out  of  the  cranium  through  the  foramen  ovale.  It  then 
divides  into  two  portions — external  and  internal. 

The  EXTERNAL  DIVISION,  into  which  nearly  the  whole  of  the 
motor  root  may  be  traced,  separates  into  five  or  six  branches 
for  the  supply  of  the  muscles  of  the  temporo-maxillary  region. 

The  masseteric  branch,  passing  over  the  external  pterygoid 
muscle  and  behind  the  tendon  of  the  temporal,  crosses  the  sig- 


EXTERNAL  DIVISION. 


177 


moid  notch  with  the  masseteric  artery,  and  is  distributed  to  the 
masseter  muscle. 

The    deep   temporal  branches,  two  in  number,   anterior  and 

Fig.  52. 


THE  BRANCHES  OP  THE  FIFTH  NERVE. — 1.  The  Casserian  ganglion.  2.  The 
ophthalmic  nerve.  3.  The  frontal  nerve.  4.  Its  supra-trochlear  branch.  5.  The 
IJM  hrvinal  nerve.  6.  The  nasal  nerve.  7.  Its  branch  of  communication  with 
the  ciliary  ganglion.  8.  The  passage  of  the  nerve  through  the  anterior  ethmoi- 
dal  foramen.  9.  The  infra-trochlear  nerve.  10.  The  superior  maxillary  nerve. 
11.  Its  orbital  branch.  12.  The  branches  of  communication  with  Meckel's  gan- 
glion. 13.  The  posterior  dental  branches.  14.  Middle  dental  branches.  15. 
The  anterior  dental  branches.  16.  The  infra-orbital  branches.  17.  The  infe- 
rior maxillary  nerve.  18.  Its  external  or  muscular  division.  19.  The  internal 
division  of  the  inferior  maxillary  nerve.  The  arrow  marks  the  separation  of 
these  two  divisions  of  the  nerve  by  the  external  pterygoid  muscle.  20.  The 
gustatory  nerve.  21.  The  branch  of  communication  with  the  submaxillary 
ganglion.  22.  The  inferior  dental  nerve,  arising  by  two  roots.  23.  Its  mylb- 
hyoidean  branch.  24.  The  auricular  nerve.  25.  Its  branch  of  communication 
with  the  facial  nerve. 

posterior,  pass  between  the  external  pterygoid  muscle  and  the 
side  of  the  cranium,  to  be  distributed  to  the  temporal  muscle. 

The  buccal  branch  is  of  large  size,  and  pierces  the  lower  fibres 
of  the  external  pterygoid  muscle  at  its  anterior  part.  It  sends 
a  branch  to  the  external  pterygoid  muscle,  and  is  then  distributed 
to  the  buccinator,  where  it  communicates  with  the  facial  nerve. 

The  internal  pterygoid  branch  is  a  long  and  slender  nerve, 
which  passes  inwards  to  the  internal  pterygoid  muscle,  and  gives 
filaments  in  its  course  to  the  tensor  palati  and  tensor  tympani. 


ITS  THE   DISSECTOR. 

This  nerve  is  remarkable  for  its  connection  with  the  otic  gan- 
glion, to  which  it  is  closely  attached. 

The  external  pterygoid  branch  is  commonly  derived  from  the 
buccal  nerve. 

The  examination  of  some  of  the  preceding  nerves  will  have  required 
the  drawing  aside  of  the  external  pterygoid,  and  even,  as  in  the  case  of 
the  buccal  nerve,  the  division  of  some  of  its  fibres.  The  muscle  must 
now  be  entirely  removed,  in  order  to  see  the  branches  of  the  internal 
division  of  the  inferior  maxillary  nerve,  which  lie  behind  it. 

The  INTERNAL  DIVISION  splits  into  three  branches — auriculo- 
temporal,  inferior  dental,  and  gustatory. 

The  AURICULO-TEMPORAL  NERVE  passes  backwards  behind  the 
articulation  of  the  lower  jaw,  and  enters  the  parotid  gland,  where 
it  divides  into  two  temporal  branches.  It  generally  consists  of 
two  cords,  between  which  the  arteria  meningea  media  takes  its 
course  to  the  foramen  spinosum. 

Its  branches  are,  a  small  branch  to  the  temporo-maxillary 
articulation  ;  two  or  three  small  branches  to  the  parotid  gland  ; 
two  branches  to  the  meatus  auris,  which  enter  the  canal  between 
the  fibro-cartilage  and  the  processus  auditorius ;  "two  auricular 
branches  to  the  pinna ;  a  communicating  branch  to  the  otic  gan- 
glion ;  two  communicating  branches  to  the  facial  nerve ;  and  the 
temporal  branches. 

The  auricular  branches,  superior  and  inferior,  are  distributed 
to  the  pinna  above  and  below  the  meatus.  The  inferior  branch 
communicates  with  the  sympathetic. 

The  branches  which  communicate  with  the  facial  nerve  em- 
brace the  external  carotid  artery  in  their  course. 

The  temporal  branches  are  anterior  and  posterior.  The  ante- 
rior accompanies  the  temporal  artery,  and  supplies  the  integu- 
ment of  the  temporal  region,  communicating  with  the  branches 
of  the  facial  and  supraorbital  nerve;  the  latter  is  distributed  to 
the  upper  part  of  the  pinna,  the  attrahens  aurem  muscle,  and  the 
integument  of  the  posterior  part  of  the  temple. 

The  INFERIOR  DENTAL  NERVE,  the  largest  of  the  three  branches 
of  the  internal  division  of  the  inferior  maxillary,  passes  down- 
wards with  the  inferior  dental  artery,  at  first  between  the  two 
pterygoid  muscles,  and  then  between  the  internal  lateral  liga- 
ment and  the  ramus  of  the  lower  jaw,  to  the  dental  foramen.  It 
then  runs  along  the  canal  in  the  inferior  maxillary  bone,  distri- 
buting branches  (inferior  maxillary  plexus)  to  the  teeth  arid 
gums,  and  divides  into  two  terminal  branches — incisive  and 
mental. 

The  branches  of  the  inferior  dental  nerve,  besides  those  given 
to  the  teeth,  are  the  mylo-hyoidean  and  the  two  terminal 
branches. 


GUSTATORY   NERVE.  179 

The  mylo-hyoidean  branch  quits  the  nerve  just  as  it  is  about 
to  enter  the  dental  foramen.  This  branch  pierces  the  insertion 
of  the  internal  lateral  ligament,  and  descends  along  a  groove  in 
the  bone  to  the  inferior  surface  of  the  mylo-hyoid  muscle,  to 
which,  and  to  the  anterior  belly  of  the  digastricus,  it  is  dis- 
tributed. 

The  incisive  branch  is  continued  forwards  to  the  symphysis  of 
the  jaw,  to  supply  the  incisor  teeth. 

The  mental  or  labial  branch  emerges  from  the  jaw  at  the  mental 
foramen,  beneath  the  depressor  anguli  oris,  and  divides  into 
branches  which  supply  the  muscles  and  integument  of  the  lower 
lip  and  chin,  and  communicate  with  the  facial  nerve. 

The  mylo-hyoidean  nerve  is  seen  in  the  dissection  of  the  mylo-hyoideus 
muscle,  when  the  submaxillary  region  is  turned  upwards.  It  is,  how- 
ever, better  seen  when  a  section  is  made  through  the  body  of  the  lower 
jaw  a  little  to  the  side  of  the  symphysis,  and  the  jaw  is  drawn  aside, 
after  the  detachment  of  the  mylo-hyoideus  muscle  and  buccinator, 
together  with  the  pterygo-maxillary  ligament  and  that  portion  of  the 
superior  constrictor  which  is  connected  with  the  lower  jaw.  If  this  pre- 
paration is  not  made  for  the  mylo-hyoidean  nerve,  it  is  necessary  in 
tracing  the  course  of  the  following  nerve. 

The  GUSTATORY  NERVE  descends  between  the  two  pterygoid 
muscles,  and  makes  a  gentle  curve  forwards  to  the  side  of  the 
tongue,  along  which  it  takes  its  course  to  the  tip.  On  the  side 
of  the  tongue  it  is  flattened,  and  gives  off  numerous  branches, 
which  are  distributed  to  the  mucous  membrane  and  papillae. 

In  the  upper  part  of  its  course  the  gustatory  nerve  lies  be- 
tween the  external  pterygoid  muscle  and  the  pharynx,  next 
between  the  two  pterygoid  muscles,  then  between  the  internal 
pterygoid  and  ramus  of  the  jaw,  and  between  the  stylo-glossus 
muscle  and  the  submaxillary  gland ;  lastly,  it  runs  along  the 
side  of  the  tongue,  resting  against  the  hyo-glossus  muscle,  and 
crossing  the  duct  of  the  submaxillary  gland,  and  is  covered  in  by 
the  mylo-hyoideus  and  mucous  membrane. 

The  gustatory  nerve,  while  between  the  pterygoid  muscles, 
often  receives  a  communicating  branch  from  the  inferior  dental ; 
lower  down  it  is  joined  at  an  acute  angle  by  the  chorda  tympani, 
a  small  nerve  which,  arising  from  the  facial  in  the  aqueductus 
Fallopii,  crosses  the  tympanum,  and  escapes  from  that  cavity 
through  the  fissura  Glaseri.  Having  joined  the  gustatory  nerve, 
the  chorda  tympani  is  continued  downwards  in  its  sheath  to  the 
submaxillary  ganglion. 

One  or  two  branches  are  given  by  the  gustatory  nerve  to  the 
submaxillary  ganglion. 

On  the  hyo-glossus  muscle  several  branches  of  communication 
join  with  branches  of  the  hypoglossal  nerve,  and  others  are  sent 
to  the  sublingual  gland  and  Wharton's  duct. 


180  THE  DISSECTOR. 

The  SUBMAXILLARY  GANGLION,  of  small  size  and  reddish  color, 
is  situated  on  the  submaxillary  gland,  in  close  relation  with  the 
gustatory  nerve,  and  near  the  posterior  border  of  the  mylo- 
hyoideus  muscle. 

Its  branches  of  distribution,  six  or  eight  in  number,  divide 
into  many  filaments,  which  supply  the  side  of  the  tongue,  the 
submaxillary  and  sublingual  glands,  and  Wharton's  duct. 

Its  branches  of  communication  are  two  or  three  from  and  to  the 
gustatory  nerve;  one  from  the  chorda  tympani ;  two  or  three 
which  form  a  plexus  with  branches  of  the  hypoglossal  nerve  ;  and 
one  or  two  filaments  which  pass  to  the  facial  artery,  and  com- 
municate with  the  nervi  molles  from  the  cervical  portion  of  the 
sympathetic. 

If  the  student  cut  across  the  inferior  maxillary  nerve  at  its  origin  from 
the  Casserian  ganglion,  and  after  breaking  away  the  bone  at  the  outer 
side  of  the  foramen  ovale  draw  the  nerve  outwards,  he  may  find  lying 
against  the  nerve,  close  to  its  exit  from  the  foramen  ovale,  a  small  oval- 
shaped  body — the  otic  ganglion.  Another  guide  to  this  small  ganglion 
is  the  internal  pterygoid  nerve,  upon  which  the  ganglion  is  placed. 
Unless  the  subject  be  fresh,  the  dissector  may  fail  to  discover  the  gan- 
glion, which,  to  make  it  out  clearly  with  its  branches,  requires  a  fresh 
subject  and  a  special  dissection.  If  the  latter  can  be  obtained,  the 
ganglion  is  best  found  by  dissecting  from  within  ;  taking  the  Eustachian 
tube,  against  which  it  lies,  and  the  internal  pterygoid  nerve,  as  guides 
to  its  position. 

The  OTIC  GANGLION  (Arnold's)  is  a  small  oval-shaped  and  flat- 
tened ganglion,  situated  upon  the  internal  pterygoid  nerve,  and 
appearing  like  a  swelling  of  that  nerve.  It  lies  against  the  inner 
surface  of  the  inferior  maxillary  nerve,  close  to  the  foraman  ovale, 
and  is  in  relation  internally  with  the  Eustachian  tube  and  tensor 
palati  muscle,  and  behind  with  the  arteria  meningea  media. 

The  branches  of  the  otic  ganglion  are  seven  in  number ;  two  of 
distribution,  and  five  of  communication. 

The  branches  of  distribution  are,  a  small  filament  to  the  tensor 
tympani  muscle,  and  one  or  two  to  the  tensor  palati  muscle. 

The  branches  of  communication  are,  one  or  two  filaments  from 
the  inferior  maxillary  nerve  (short  root)  ;  one  or  two  filaments 
from  the  auriculo-temporal  nerve  ;  filaments  from  the  nervi  molles 
of  the  arteria  meningea  media  and  the  nervus  petrosus  superjicialis 
minor  (long  root).  The  latter  nerve  ascends  from  the  ganglion 
to  a  small  canal  situated  between  the  foramen  ovale  and  foramen 
spinosum,  and  passes  backwards  on  the  petrous  bone  to  the  hiatus 
Fallopii,  where  it  divides  into  two  filaments.  One  of  these  fila- 
ments enters  the  hiatus  and  joins  the  intumescentia  gangliformis 
of  the  facial ;  the  other  passes  to  a  minute  foramen  nearer  the  base 
of  the  petrous  bone,  and  enters  the  tympanum,  where  it  communi- 
cates with  a  branch  of  Jacobson's  nerve. 


SUPERIOR   MAXILLARY   NERVE. 


181 


The  SUPERIOR  MAXILLARY  NERVE,  issuing  from  the  middle  of 
the  Casserian  ganglion,  passes  through  the  foramen  rotundum, 
then  crosses  the  spheno-maxillary  fossa,  and  enters  the  canal  in 


Fig.  53. 


THE  OTIC  GANGLION  SEEN 
FROM  THE  INNER  SIDE. — a. 
Internal  pterygoid  muscle. 
b.  Carotid  artery  with  the 
sympathetic.  c.  Mastoid 
process,  d.  Membrane  of 
tympanum.  e.  Bones  of 
tympanum.  1.  Casserian 
ganglion.  2.  First  division 
of  fifth.  3.  Second  division. 
4.  Third  division.  5.  Branch 
to  tensor  palati.  6.  Small 
superficial  petrosal  nerve. 
7.  Chorda  tympani.  The 
nerve  of  the  internal  ptery- 
goid muscle  is  seen  on  the 
muscle. 


the  floor  of  the  orbit,  along  which  it  runs  to  the  infra-orbital 
foramen.  Emerging  on  the  face,  beneath  the  levator  labii  supe- 
rioris  muscle,  it  divides  into  a  number  of  branches,  which  form  a 
plexus  with  the  facial  nerve. 

The  branches  of  the  superior  maxillary  nerve  are  divisible 
into  three  groups:  Those  which  are  given  off  in  the  spheno- 
maxillary  fossa ;  those  in  the  infra-orbital  canal ;  and  those  on 
the  face.  They  may  be  thus  arranged : — 

(  Orbital,  or  temporo-malar, 
Spheno-maxillary  fossa,  •<  Spheno-palatine, 

(  Posterior  dental. 

?  Middle  dental, 

(Anterior  dental. 

( Muscular, 

(Cutaneous. 

The  orbital  or  temporo-malar  branch  enters  the  orbit  through 
the  spheno-maxillary  fissure,  and  divides  into  two  branches — 
temporal  and  malar :  the  temporal  branch  ascends  along  the 
outer  wall  of  the  orbit,  and  after  receiving  a  branch  from  the 
lachrymal  nerve,  passes  through  a  canal  in  the  malar  bone,  and 
enters  the  temporal  fossa ;  it  then  pierces  the  temporal  muscle 
and  fascia,  and  is  distributed  to  the  integument  of  the  temple 
and  side  of  the  forehead,  communicating  with  the  facial  and 
anterior  temporal  nerve.  In  the  temporal  fossa  it  communicates 
16 


Infra-orbital  canal, 
On  the  face, 


182  THE   DISSECTOR. 

with  the  deep  temporal  nerves.  The  malar,  or  inferior,  branch 
(subcutaneous  malse)  takes  its  course  along  the  lower  angle  of 
the  outer  wall  of  the  orbit,  and  emerges  upon  the  cheek  through 
an  opening  in  the  malar  bone,  passing  between  the  fibres  of  the 
orbicularis  palpebrarum  muscle.  It  communicates  with  branches 
of  the  infra-orbital  ajnd  facial  nerve. 

The  spheno-palatine  branches,  two  in  number,  pass  downwards 
to  the  spheno-palatine,  or  Meckel's  ganglion. 

The  posterior  dental  branches,  two  in  number,  pass  down- 
wards upon  the  tuberosity  of  the  superior  maxillary  bone,  where 
one  enters  a  canal  in  the  bone  and  is  distributed  to  the  molar 
teeth  and  lining  membrane  of  the  antrum,  and  communicates 
with  the  anterior  dental  nerve;  while  the  other,  lying  externally 
to  the  bone,  is  distributed  to  the  gums  and  buccinator  muscle. 

The  middle  and  anterior  dental  branches  descend  to  the  corre- 
sponding teeth  and  gums;  the  former  beneath  the  lining  mem- 
brane of  the  antrum,  the  latter  through  distinct  canals  in  the 
walls  of  the  bone.  Previously  to  their  distribution,  the  dental 
nerves  form  a  plexus  (superior  maxillary  plexus)  in  the  outer 
wall  of  the  superior  maxillary  bone,  immediately  above  the  alveo- 
lus. From  this  plexus  the  filaments  are  given  off  which  supply 
the  pulps  of  the  teeth,  gums,  mucous  membrane  of  the  floor  of 
the  nares  and  the  palate. 

The  muscular  and  cutaneous  branches  are  the  terminating  fila- 
ments of  the  nerve ;  they  supply  the  muscles,  integument,  and 
mucous  membrane  of  the  lower  eyelid,  cheek,  nose,  arid  lip,  and 
form  a  plexus  by  their  communications  with  the  facial  nerve. 

The  student  may  now  proceed  to  examine  the  small  ganglion  con- 
nected with  the  superior  maxillary  nerve,  and  situated  in  the  spheno- 
maxillary  fossa.  To  ascertain  the  precise  position  of  the  ganglion,  and 
the  direction  of  its  branches,  he  should  refer  to  the  skull,  and  make 
such  observations  with  regard  to  the  removal  of  parts  of  the  bones  as 
will  enable  him  to  obtain  a  good  view  of  the  contents  of  the  cavity.  The 
branches  proceeding  downwards  from  the  superior  maxillary  nerve  are 
the  proper  guide  to  the  ganglion ;  the  nasal  branches,  which  pass  into 
the  nose  through  the  spheno-palatine  foramen,  can  only  be  followed  on 
a  section  of  the  skull,  and  must  be  left  for  a  later  period  of  the  dis- 
section :  the  same  remark  applies  to  the  palatine  nerves ;  but  the 
Vidian  may  be  traced  backwards  through  the  pterygoid  canal,  by  cut- 
ting away  with  care  the  root  of  the  pterygoid  process,  and  may  then  be 
followed  to  the  petrous  portion  of  the  temporal  bone,  where  it  joins  the 
facial  nerve. 

The  SPHENO-PALATINE,  or  MECKEL'S  GANGLION  is  situated  in 
the  spheno-maxillary  fossa,  at  a  short  distance  below  the  supe- 
rior maxillary  nerve,  with  which  it  is  connected  by  the  two 
spheno-palatine  nerves.  It  is  of  small  size,  triangular  in  shape, 
of  a  reddish-gray  color,  and  is  placed  on  the  posterior  part  of 
the  spheno-palatine  nerves,  which  it  only  partially  involves. 


SPHENO-PALATINE  GANGLION.  183 

Its  branches  are  divisible  into  four  groups,  ascending,  descend- 
ing, internal,  and  posterior. 

The  ascending  branches  are  three  or  four  small  filaments  which 
are  distributed  to  the  periosteum  of  the  orbit. 

The  descending  branches  are  the  three  palatine  nerves — ante- 
rior, middle,  and  posterior. 

The  anterior  or  large  palatine  nerve  descends  from  the  ganglion 
through  the  posterior  palatine  canal,  and  emerges  at  the  poste- 
rior palatine  foramen.  It  then  passes  forwards  in  the  substance 
of  the  hard  palate  to  which  it  is  distributed,  and  communicates 
with  the  naso-palatine  nerve.  While  in  the  posterior  palatine 
canal,  this  nerve  gives  off  several  branches  (inferior  nasal), 
which  enter  the  nose  through  openings  in  the  palate  bone,  and 
are  distributed  to  the  middle  and  inferior  meatus,  the  inferior 
spongy  bone,  and  the  antrum. 

The  middle  or  external  palatine  nerve  descends,  externally  to 
the  preceding,  to  the  posterior  palatine  foramen,  and  distributes 
branches  to  the  tonsil,  soft  palate,  and  uvula. 

The  posterior  or  small  palatine  nerve  passes  down  through  a 
separate  canal,  and  emerges  through  a  separate  opening  behind 
the  posterior  palatine  foramen.  It  is  distributed  to  the  hard 
palate  and  gums,  near  its  point  of  exit,  as  also  to  the  tonsil,  soft 
palate,  and  uvula. 

The  internal  branches  are  the  superior  nasal  and  the  naso- 
palatine. 

The  superior  nasal,  four  or  five  in  number,  enter  the  nasal 
fossa  through  the  spheno-palatine  foramen,  and  are  distributed 
to  the  mucous  membrane  of  the  superior  meatus  and  superior 
and  middle  spongy  bones. 

The  naso-palatine  nerve  enters  the  nasal  fossa  with  the  nasal 
nerves,  and  crosses  the  roof  of  the  nares  to  reach  the  septum,  to 
which  it  gives  filaments.  It  then  curves  downwards  and  for- 
wards to  the  naso-palatine  canal,  and  passes  through  that  canal 
to  the  palate,  to  which  and  to  the  papilla  behind  the  incisor 
teeth  it  is  distributed.  This  nerve  was  described  by  Cloquet  as 
uniting  with  its  fellow  in  the  anterior  palatine  canal,  and  consti- 
tuting the  naso-palatine  ganglion.  The  existence  of  this  gan- 
glion is  disputed. 

The  posterior  branches  are  the  Yidian  or  pterygoid  nerve  and 
the  pharjngeal. 

The  Vidian  nerve  passes  directly  backwards  from  the  spheno- 
palatine  ganglion,  through  the  pterygoid  or  Yidian  canal,  to 
the  foramen  lacerum  basis  cranii,  where  it  divides  into  two 
branches,  the  carotid  and  petrosal.  The  carotid  branch  (n. 
petrosus  profundiis)  crosses  the  foramen  lacerum,  surrounded  by 
the  cartilaginous  substance  which  closes  that  opening,  and  enters 


184 


THE   DISSECTOR. 


the  carotid  canal  to  join  the  carotid  plexus.  Thepetrosal  branch 
(nervus  petrosus  superficialis  major)  enters  the  cranium  through 
the  foramen  lacerum  basis  cranii,  piercing  the  cartilaginous  sub- 


Fig.  54. 


THE  CRANIAL  GAN- 
GLIA OF  THE  SYMPA- 
THETIC NERVE.  —  1. 
The  ganglion  of  Ribes. 
2.  The  filament  by 
which  it  communicates 
with  the  carotid  plexus 
(3) .  4.  The  ciliary  or 
lenticular  ganglion, 
giving  off  ciliary 
branches  for  the  supply 
of  the  globe  of  the  eye. 
5.  Part  of  the  inferior 
division  of  the  third 
nerve,  receiving  a  short 
thick  branch  from  the 
ganglion.  6.  Part  of 
the  nasal  nerve,  receiv- 
ing a  longer  branch 
from  the  ganglion.  7. 
A  slender  filament  sent 
directly  backwards 
from  the  ganglion  to 
the  sympathetic 

branches  in  the  cavernous  sinus.  8.  Part  of  the  sixth  nerve  in  the  cavernous 
sinus,  receiving  two  branches  from  the  carotid  plexus.  9.  Meckel's  ganglion 
(spheno-palatine) .  10.  Its  ascending  branches,  communicating  with  the  supe- 
rior maxillary  nerve.  11.  Its  descending  branches,  the  posterior  palatine.  12. 
Its  anterior  branches,  spheno-palatine  or  nasal.  13.  The  naso-palatine  branch, 
one  of  the  nasal  branches.  *  The  point  where  Cloquet  imagined  the  naso- 
palatine  ganglion  to  be  situated.  14.  The  posterior  branch  of  the  ganglion,  the 
Vidian  nerve.  15.  Its  carotid  branch,  communicating  with  the  carotid  plexus. 
16.  Its  petrosal  branch,  joining  the  angular  bend  of  the  facial  nerve.  17.  The 
facial  nerve.  18.  The  chorda  tympani  nerve,  which  descends  to  join  the  gus- 
tatory nerve.  19.  The  gustatory  nerve.  20.  The  submaxillary  ganglion,  re- 
ceiving the  chorda  tympani  nerve  from  the  gustatory.  21.  The  superior  cervi- 
cal ganglion  of  the  sympathetic. 

stance,  and  passes  backwards  beneath  the  Casserian  ganglion 
and  dura  mater,  embedded  in  a  groove  on  the  anterior  surface  of 
the  petrous  bone,  to  the  hiatus  Fallopii.  In  the  hiatus  Fallopii 
it  receives  a  branch  from  Jacobson's  nerve,  and  terminates  in  the 
intumescentia  gangliformis  of  the  facial  nerve. 

The  pharyngeal  nerve  is  a  small  branch  which  passes  back- 
wards through  the  pterygo-palatine  canal  with  the  pterygo-pala- 
tine  artery,  to  be  distributed  to  the  mucous  membrane  of  the 
Eustachian  tube  and  neighboring  part  of  the  pharynx. 

While  examining  the  nerves  proceeding  from  Meckel's  gan- 
glion, the  dissector  will  observe  the  branches  of  the  internal 
maxillary  artery  by  which  they  are  accompanied  :  the  spheno- 
palatine  artery  enters  the  nose  with  the  superior  nasal  nerves ; 


INTERNAL   CAROTID  ARTERY.  185 

the  descending  palatine  artery  passes  down  to  the  palate  with 
the  palatine  nerves  ;  and  the  Yidian  artery  accompanies  the 
Vidian  nerve. 

INTERNAL  CAROTID  ARTERY. 

The  student  may  now  proceed  to  examine  the  internal  carotid  artery, 
with  which  view  he  may  remove  any  structure  that  conceals  the  artery. 
The  internal  jugular  vein  lies  to  its  outer  side  ;  it  is  crossed  in  front  by 
the  stylo-glossus  and  stylo-pharyngeus  muscle  and  stylo-hyoid  ligament, 
and  higher  up  it  has  the  parotid  gland  ;  to  its  inner  side  is  the  pharynx 
and  ascending  pharyngeal  artery  (p.  170),  and  behind  it  has  the  verte- 
bral column,  the  rectus  anticus  major  muscle,  and  some  important 
nerves. 

As  the  student  may  wish  to  remove  the  styloid  process,  he  should 
observe  the  relative  position  of  the  parts  connected  with  it.  Passing 
forward  from  the  apex  of  this  process  to  the  angle  of  the  jaw  is  the  stylo- 
maxillary  ligament,  a  process  of  the  deep  cervical  fascia  which  separates 
the  submaxillary  from  the  parotid  gland.  Proceeding  also  from  the 
apex  of  the  process  and  partly  from  this  ligament,  is  the  stylo-glossus,  the 
highest  of  the  three  styloid  muscles.  Arising  from  the  middle  of  the 
styloid  process,  and  coming  forwards  to  the  body  of  the  os  hyoides,  is 
the  stylo-hyoideus  muscle,  middle  in  position  to  the  others — but  the  most 
superficial  of  the  three.  Next  the  stylo-pharyngeus  may  be  seen  arising 
from  the  inner  side  of  the  base  of  the  styloid  process,  and  passing  down- 
wards almost  vertically  to  the  middle  of  the  pharynx,  the  lowest  and 
deepest  of  the  three  muscles.  Lastly,  there  is  the  stylo-hyoid  ligament,  a 
fibrous  cord  extending  from  the  apex  of  the  styloid  process  to  the  lesser 
cornu  of  the  os  hyoides.  This  ligament  is  sometimes  cartilaginous  or 
even  osseous,  and  may  be  jointed  with  the  styloid  process  above  and  the 
lesser  cornu  of  the  os  hyoides  below.  At  its  lower  part  it  is  behind  the 
hyo-glossus  muscle,  and  gives  origin  to  part  of  the  middle  constrictor 
muscle. 

The  INTERNAL  CAROTID  ARTERY  curves  slightly  outwards  at  its 
origin  from  the  common  carotid,  and  ascends  nearly  perpendicu- 
larly by  the  side  of  the  pharynx  to  the  carotid  foramen  in  the 
petrous  portion  of  the  temporal  bone.  It  then  passes  inwards 
along  the  carotid  canal ;  forwards  by  the  side  of  the  sella  tur- 
cica ;  and  upwards  by  the  anterior  clinoid  process,  where  it 
pierces  the  dura  mater,  and  divides  into  three  terminal  branches. 

The  course  of  this  artery  is  remarkable  for  the  number  of 
angular  curves  which  it  forms ;  one  or  two  of  these  flexures  are 
sometimes  seen  in  the  cervical  portion,  near  the  base  of  the 
skull ;  by  the  side  of  the  sella  turcica,  it  resembles  the  Italic  let- 
ter S  placed  horizontally. 

The  internal  carotid,  which  at  first  lies  on  the  same  plane  with 
the  external  carotid,  soon  gets  behind  the  latter,  and  higher  up 
is  separated  from  it  by  the  stylo-glossus,  stylo-pharyngeus,  stylo- 
hyoid  ligament,  and  parotid  gland ;  and  is  crossed  by  the  glosso- 
pharyngeal  nerve.  To  its  inner  side  is  the  pharynx,  tonsil,  and 
ascending  pharyngeal  artery  ;  to  its  outer  side,  the  internal  jugu- 

16* 


186  THE   DISSECTOR. 

lar  vein  ;  between  the  vein  and  artery  near  the  base  of  the 
skull,  the  glosso-pharyngeal,  pneumogastric,  and  hypoglossal 
nerve  ;  and  externally  to  the  vein,  the  loop  between  the  first  and 
second  cervical  nerves.  Behind,  the  artery  rests  on  the  rectus 
anticus  major,  the  superior  cervical  ganglion  of  the  sympathetic, 
the  pharyngeal  and  superior  laryngeal  nerves  being  interposed. 

To  follow  the  internal  carotid  artery  through  the  petrous  portion  of  the 
temporal  bone,  it  is  necessary  to  make  a  section  of  the  skull  from  the  back 
part  of  the  mastoid  process  to  the  carotid  foramen,  keeping  close  to  the 
outside  of  the  styloid-mastoid  foramen.  This  piece  of  bone  may  then  be 
broken  away  and  preserved  for  the  subsequent  examination  of  the  mem- 
brana  tympani,  ossicula  auditus,  and  chorda  tympani  nerve.  The  anterior 
wall  of  the  carotid  canal  is  to  be  furthermore  broken  away  by  the  chisel. 

The  petrous  portion  of  the  artery  is  in  close  contact  with  the 
periosteal  lining  of  the  carotid  canal  derived  from  the  dura  mater, 
and  is  embraced  by  the  nerves  of  the  carotid  plexus.  At  the 
extremity  of  the  canal,  the  artery  is  in  relation  with  the  under 
surface  of  the  Casserian  ganglion. 

By  the  side  of  the  sella  turcica  the  internal  carotid  artery  is 
situated  in  the  inner  wall  of  the  cavernous  sinus,  and  is  in  relation 
by  its  outer  side  with  the  lining  membrane  of  the  sinus,  the  sixth 
nerve,  and  the  ascending  branches  of  the  carotid  plexus.  The 
third,  fourth,  and  ophthalmic  nerve  are  placed  in  the  outer  wall 
of  the  sinus,  and  are  separated  by  the  latter  from  the  artery. 

The  cerebral  portion  of  the  artery  is  invested  by  a  sheath  of 
the  arachnoid,  and  is  in  close  relation  with  the  optic  nerve. 

The  branches  of  the  internal  carotid  artery  are  derived  from  its 
cranial  portion,  and  are  as  follows  : — 

Tympanic,  Anterior  cerebral, 

Anterior  meningeal,          Middle  cerebral, 
Ophthalmic,  Posterior  communicating, 

Choroidean. 

The  tympanic  is  a  small  branch  given  off  in  the  carotid  canal ; 
it  enters  the  tympanum,  and  inosculates  with  the  tympanic  branch 
of  the  internal  maxillary  and  with  the  stylo-mastoid  artery. 

The  anterior  meningeal,  arising  from  the  artery  after  its  escape 
from  the  carotid  canal,  is  distributed  to  the  Casserian  ganglion 
and  dura  mater  of  the  middle  fossa  of  the  cranium. 

The  ophthalmic  artery  is  given  off  close  to  the  anterior  clinoid 
process,  and  passes  through  the  optic  foramen  lying  to  the  outer 
side  of  the  optic  nerve.  Its  distribution  within  the  orbit  has 
been  already  described  (page  137). 

The  anterior  and  middle  cerebral  artery,  and  the  posterior  com- 
municating, the  terminal  branches  of  the  internal  carotid,  will  be 
described  with  the  anatomy  of  the  brain  in  the  next  chapter. 

INTERNAL  JUGULAR  YEIN. — The  vein  corresponding  with  the 


FACIAL   NERVE.  1ST 

internal  carotid  artery,  and  which,  lower  in  the  neck,  accompanies 
the  common  carotid,  is  the  internal  jugular.  It  commences  at 
the  jugular  fossa,  in  the  foramen  lacerum  posterius  basis  cranii, 
where  it  receives  the  blood  from  the  sinuses  of  the  dura  mater. 
At  its  origin,  the  internal  jugular  vein  is  posterior  to  the  internal 
carotid  artery,  but  soon  gets  to  its  outer  side,  and  keeps  that 
position  in  relation  to  the  common  carotid  artery  in  its  course 
through  the  neck.  The  eighth  pair  of  nerves,  at  its  exit  from 
the  cranium,  lies  in  front  and  to  the  inner  side  of  the  vein ;  the 
hypoglossal  nerve  being  behind  its  inner  border.  The  glosso- 
pharyngeal  and  hypoglossal  nerves  then  pass  forwards,  between 
the  inner  side  of  the  vein  and  the  internal  carotid  artery ;  the 
pneumogastric,  and  superior  cervical  ganglion  of  the  sympathetic, 
are  placed  at  its  inner  side ;  and  the  spinal  accessory  nerve  crosses 
behind,  and  sometimes  in  front  of  it,  at  its  upper  part. 

The  internal  jugular  vein  receives  the  facial,  occipital,  lingual, 
pharyugeal,  and  superior  and  middle  thyroid  veins. 

FACIAL  NERVE. 

The  section  already  prescribed  (page  185)  for  the  demonstration  of  the 
internal  carotid  may  be  made  subservient  to  the  examination  of  the  facial 
nerve  in  its  course  through  the  petrous  bone.  With  this  object  the  saw 
should  not  be  carried  too  far  or  too  deeply,  and  used  only  to  divide  such 
parts  as  may  not  be  conveniently  broken  away  with  the  chisel  and 
hammer.  The  outer  boundary  of  the  stylo-mastoid  foramen  being  laid 
open,  the  wall  of  the  aqueductus  Fallopii  may  be  broken  away  in  its 
course  along  the  internal  boundary  of  the  tympanum  to  the  anterior  sur- 
face of  the  petrous  bone,  and  thence  backwards  to  the  meatus. 

The  FACIAL  NERVE  (portio  dura  of  the  seventh  pair)  passes  into 
the  meatus  auditorius  internus,  with  the  auditory  nerve  or  portio 
mollis,  lying  at  first  to  the  inner  side  and  then  upon  the  latter. 
At  the  bottom  of  the  meatus  it  enters  the  aqueductus  Fallopii, 
and  takes  its  course  forwards  to  the  hiatus  Fallopii,  in  the  anterior 
surface  of  the  petrous  bone  ;  it  then  curves  backwards  towards  the 
tympanum,  and  descends  in  the  inner  wall  of  that  cavity  to  the 
stylo-mastoid  foramen,  through  which  it  emerges. 

While  in  the  meatus  auditorius,  the  facial  nerve  communicates 
with  the  auditory  nerve  by  one  or  two  filaments.  At  the  angu- 
lar bend  of  the  aqueductus  Fallopii,  where  the  nerve  is  close  to 
the  anterior  surface  of  the  petrous  bone,  it  presents  a  gangliform 
swelling  (intumescentiagangliformis:  ganglion  geniculare),  which 
receives  the  petrosal  branch  of  th'e  Vidian  nerve  and  that  of  the 
otic  ganglion,  and  sends  a  filament  back  to  the  auditory  nerve. 
Behind  the  tympanum  it  is  joined  by  one  or  two  twigs  from  the 
auricular  branch  of  the  pneumogastric  ;  and  lower  down  it  gives 
off  a  tympanic  branch  to  the  stapedius  muscle,  and  the  chorda 
tympani  nerve. 


188 


THE   DISSECTOR. 


The  chorda  tympani  nerve  may  now  be  sought  for  on  the  removed  section 
of  the  bone  previously  made,  and  may  be  traced  across  the  tympanum. 

Fig.  55 


THB  DISTRIBUTION  OF  THE  FACIAL  NERVE  AND  THE  BRANCHES  OF  THE  CER- 
VICAL PLEXUS. — 1.  The  facial  nerve,  escaping  from  the  stylo-mastoid  foramen, 
and  crossing  the  ramus  of  the  lower  jaw ;  the  parotid  gland  has  been  removed 
in  order  to  see  the  nerve  more  distinctly.  2.  The  posterior  auricular  branch  ; 
the  digastric  and  stylo-mastoid  filaments  are  seen  near  the  origin  of  this  branch. 
3.  Temporal  branches,  communicating  with  (4)  the  branches  of  the  frontal 
nerve.  5.  Facial  branches,  communicating  with  (6)  the  infra-orbital  nerve.  7. 
Facial  branches,  communicating  with  (8)  the  mental  nerve.  9.  Cervico -facial 
branches,  communicating  with  (10)  the  superficialis  colli  nerve,  and  forming  a 
plexus  (11)  over  the  submaxillary  gland.  The  distribution  of  the  branches  of 
the  facial  in  a  radiated  direction  over  the  side  of  the  face  constitutes  the  pes 
anserinus.  12.  The  auricularis  magnus  nerve,  one  of  the  ascending  branches 
of  the  cervical  plexus.  13.  The  occipitalis  minor,  ascending  along  the  posterior 
border  of  the  sterno-mastoid  muscle.  14.  The  superficial  and  deep  descending 
branches  of  the  cervical  plexus.  15.  The  spinal  accessory  nerve,  giving  off  a 
branch  to  the  external  surface  of  the  trapezius  muscle.  16.  The  occipitalis 
major  nerve,  the  posterior  branch  of  the  second  cervical  nerve. 

The  chorda  tympani  nerve  quits  the  facial  just  above  the  stylo- 
mastoid  foramen,  and  ascends  by  a  distinct  canal  to  the  upper 
part  of  the  posterior  wall  of  the  tympanum,  which  it  enters 
through  an  opening  situated  between  the  base  of  the  pyramid 
and  the  attachment  of  the  membrana  tympani.  It  then  crosses 
the  tympanum,  between  the  handle  of  the  malleus  and  long  pro- 
cess of  the  incus  to  the  anterior  inferior  angle  of  the  cavity,  and 


GLOSSO-PHARYNGEAL  NERVE. 


189 


escapes  through  a  distinct  opening  Fig-  56. 

in  the  fissura  Glaseri,  to  join   the 

gustatory  nerve   at  an  acute  angle 

between  the  two  pterygoid  muscles 

(page  179).     In  its  course  through 

the  tympanum  it  is  inclosed  within  a 

sheath  of  mucous  membrane. 

EIGHTH  PAIR  OF  NERVES. — The 
eighth  pair  consists  of  three  nerves — 
glosso  -  pharyngeal,  pneumogastric, 
and  spinal  accessory — which  escape 
from  the  cranium  at  the  foramen 
lacerum  posterius,  internally  and  an- 
teriorly to  the  internal  jugular  vein. 
At  their  point  of  exit  the  glosso- 
pharyngeal  is  in  front  of  the  other 
two,  and  has  a  separate  sheath  of 
dura  mater.  The  pueumogastric  and 
spinal  accessory  are  inclosed  in  the 
same  sheath. 

The    GLOSSO-PHARYNGEAL    NERVE, 

the  smallest  of  the  three,  advances 
forwards  between  the  internal  carotid 
artery  and  jugular  vein,  and  crosses 
the  artery  to  the  lower  border  of 
the  stylo-pharyngeus  muscle;  it  then 
turns  forwards  across  the  stylo-pha- 
ryngeus, and,  getting  behind  the 
hyo-glossus  muscle,  is  distributed  to 
the  mucous  membrane  of  the  tongue, 
the  pharynx,  and  the  tonsil. 

While  in  the  jugular  fossa,  the 
nerve  presents  two  gangliform,  swell- 
ings; one,  superior,  of  small  size, 

ORIGIN  AND  DISTRIBUTION  OF  THE  EIGHTH  PAIR  OP  NERVES  OF  THE  LEFT 
SIDE. — 1.  The  medulla  oblongata.  2.  The  corpus  pyramidale  of  the  left  side. 
3.  The  corpus  olivare.  4.  The  corpus  restiforme.  5.  The  origin  of  the  glosso- 
pharyngeal  nerve.  6.  The  ganglion  of  the  glosso-pharyngeal  nerve,  or  of 
Andersch.  7.  A  branch  from  the  glosso-pharyngeal  nerve  to  the  pharyngeal 
plexus.  8.  The  origin  of  the  pneumogastric  nerve.  9.  The  upper  ganglion  of 
the  pneumogastric.  10.  The  lower  or  plexiform  ganglion  of  the  nerve.  11. 
The  pharyngeal  nerve,  descending  to  form  the  pharyngeal  plexus.  12.  The 
superior  laryngeal  nerve.  13.  A  branch  to  the  pharyngeal  plexus.  14.  Car- 
diac nerves.  15.  The  recurrent  laryngeal  nerve.  16.  Cardiac  branches  from 
the  recurrent.  17.  (Esophageal  plexus.  18.  Branches  to  the  stomach.  19. 
A  branch  which  joins  the  solar  plexus.  20.  The  origin  of  the  spinal  accessory 
nerve.  21.  Its  branches  to  the  sterno-mastoid  muscle.  22.  Terminal  branches 
to  the  trapezius.  23.  The  origin  of  the  facial  nerve,  p.  The  branches  forming 
the  pulmonary  plexuses. 


190  THE  DISSECTOR. 

and  involving  only  the  posterior  fibres  of  the  nerve — the  gan- 
glion jugulare  (Muller)  ;  the  other,  inferior,  of  larger  size,  nearly 
half  an  inch  below  the  superior,  and  occupying  the  whole  diameter 
of  the  nerve,  the  ganglion  petrosum,  or  ganglion  of  Andersch.1 

The  branches  of  the  glosso-pharyngeal  nerve  are,  branches  of 
communication  and  branches  of  distribution. 

The  branches  of  communication  proceed  chiefly  from  the  gan- 
glion of  Andersch;  they  are,  one  to  join  the  auricular  branch  of 
the  pneumogastric ;  one  to  the  ganglion  of  the  pneumogastric  ; 
one  to  the  superior  cervical  ganglion  of  the  sympathetic, ;  and 
one,  which  arises  below  the  ganglion,  and  pierces  the  posterior 
belly  of  the  digastricus  muscle,  to  join  the  facial  nerve. 

The  branches  of  distribution  are — 

Tympanic,  Pharyngeal, 

Carotid,  Tonsillitic, 

Muscular,  Lingual. 

The  tympanic  branch  (Jacobson's  nerve)  proceeds  from  the 
ganglion  of  Andersch,  or  from  the  trunk  of  the  nerve  immediately 
above  the  ganglion ;  it  enters  a  small  bony  canal  in  the  jugular 
fossa,  and  divides  into  six  branches,  which  are  distributed  upon 
the  inner  wall  of  the  tympanum,  and  establish  a  plexiform  com- 
munication (tympanic  plexus)  with  the  sympathetic  and  fifth 
pair  of  nerves.  The  branches  of  distribution  supply  the  fenestra 
rotunda,  fenestra  ovalis,  and  Eustachian  tube:  those  of  commu- 
nication join  the  carotid  plexus  in  the  carotid  canal,  the  petrosal 
branch  of  the  Yidian  nerve,  and  the  otic  ganglion. 

The  carotid  branches  are  several  filaments  which  follow  the 
trunk  of  the  internal  carotid  artery,  and  communicate  with  the 
nervi  molles  of  the  sympathetic. 

The  muscular  branch  divides  into  filaments,  which  are  distri- 
buted to  the  posterior  belly  of  the  digastricus,  stylo-hyoideus, 
stylo-pharyngeus,  and  constrictor  muscles. 

The  pharyngeal  branches  are  two  or  three  filaments,  which 
are  distributed  to  the  pharynx  and  unite  with  the  pharyngeal 
branches  of  the  pneumogastric  and  sympathetic  nerve  to  form 
the  pharyngeal  plexus. 

The  tonsiUitic  branches  proceed  from  the  glosso-pharyngeal 
nerve  near  its  termination ;  they  form  a  plexus  (circulus  tonsil- 
laris)  around  the  base  of  the  tonsil,  from  which  numerous  fila- 
ments are  given  off  to  the  mucous  membrane  of  the  fauces  and 
soft  palate.  These  filaments  communicate  with  the  descending 
palatine  branches  of  Meckel's  ganglion. 

The  lingual  branches  enter  the  substance  of  the  tongue  be- 

1  Charles  Samuel  Andersch.  Tractatus  Anatomico-Physiologica  de 
Nervis  Corporus  Human!  Aliquibis,  1797. 


PNEUMOGA6TRIC  OR  VAGUS  NERVE.        191 

neath  the  hyo-glossus  and  stylo-glossus  muscle,  and  are  distri- 
buted to  the  mucous  membrane  of  the  side  and  base  of  the 
tongue,  and  to  the  epiglottis  and  fauces. 

The  PNEUMOGASTRIC  or  VAGUS  NERVE,  the  largest  of  the  three 
divisions  of  the  eighth  pair,  at  its  escape  from  the  jugular  fora- 
men, is  inclosed  in  a  sheath  of  dura  mater,  which  is  common  to 
it  and  the  spinal  accessory.  The  nerve  takes  its  course  down 
the  side  of  the  neck,  lying  at  first  between  the  internal  carotid 
artery  and  jugular  vein,  and  then  between  and  behind  the  com- 
mon carotid  artery  and  jugular  vein,  inclosed  in  the  same  sheath, 
to  the  superior  opening  of  the  thorax,  through  which  it  passes 
to  the  lungs  and  stomach. 

In  the  jugular  foramen  the  pneumogastric  nerve  presents  a 
small  round  ganglion,  the  superior  or  jugular  ganglion;  and, 
immediately  at  its  exit,  a  gangliform  swelling  nearly  an  inch  in 
length,  the  inferior  ganglion  (plexus  gangliformis). 

The  branches  of  the  pneumogastric  nerve  are,  the  branches  of 
communication  and  the  branches  of  distribution. 

The  branches  of  communication  proceed  from  the  ganglia: 
from  the  superior  ganglion  one  or  two  branches  pass  to  the 
spinal  accessory;  one  or  two  to  the  superior  ganglion  of  the 
sympathetic;  and  one  to  the  inferior  ganglion  of  the  glosso- 
pharyngeal.  From  the  inferior  ganglion  there  pass  off  branches 
to  the  hypoglossal ;  branches  to  the  superior  cervical  ganglion 
of  the  sympathetic;  and  branches  to  the  loop  between  the  first 
and  second  cervical  nerves. 

The  branches  of  distribution  are — 

Auricular,  Superior  laryngeal, 

Pharyngeal,  Cardiac, 

Inferior  laryngeal. 

The  auricular  nerve  is  given  off  from  the  lower  part  of  the 
jugular  ganglion,  or  from  the  trunk  of  the  nerve  immediately 
below  it,  and  receives  immediately  after  its  origin  a  small  branch 
of  communication  from  the  glosso-pharyngeal.  It  then  passes 
outwards  behind  the  jugular  vein,  and  on  the  outer  side  of  that 
vessel  enters  a  small  canal  in  the  petrous  portion  of  the  temporal 
bone  near  the  stylo-mastoid  foramen.  Guided  by  this  canal  it 
reaches  the  descending  part  of  the  aqueductus  Fallopii  and  joins 
the  facial  nerve.  In  the  aqueductus  Fallopii  the  auricular  nerve 
gives  off  two  small  filaments,  one  of  which  communicates  with 
the  posterior  auricular  branch  of  the  facial,  while  the  other  is 
distributed  to  the  pinna. 

The  pharyngeal  nerve  arises  from  the  upper  part  of  the  supe- 
rior ganglion,  and  crosses  behind  the  internal  carotid  artery  to 
the  upper  border  of  the  middle  constrictor,  upon  which  it  forms 


192  THE   DISSECTOR. 

the  pharyngeal  plexus,  assisted  by  branches  from  the  glosso- 
pharyngeal,  superior  laryngeal,  and  sympathetic.  The  pharyn- 
geal plexus  is  distributed  to  the  muscles  and  mucous  membrane 
of  the  pharynx. 

The  superior  laryngeal  nerve  arises  from  the  inferior  ganglion, 
and  descends  behind  the  internal  carotid  artery  to  the  -opening 
in  the  thyro-hyoidean  membrane,  through  which  it  passes  with 
the  superior  laryngeal  artery,  and  is  distributed  to  the  mucous 
membrane  of  the  larynx  and  arytenoideus  muscle.  On  the 
latter,  and  behind  the  cricoid  cartilage,  it  communicates  with 
the  recurrent  laryngeal  nerve.  Behind  the  internal  carotid  it 
gives  off  the  external  laryngeal  branch,  which  sends  a  twig  to 
the  pharyngeal  plexus,  and  then  descends  to  supply  the  inferior 
constrictor  and  crico-thyroid  muscle  and  thyroid  gland.  This 
branch  communicates  inferiorly  with  the  recurrent  laryngeal  and 
sympathetic  nerve. 

The  cardiac  branches,  two  or  three  in  number,  arise  from  the 
upper  and  lower  part  of  the  nerve.  Those  from  above  commu- 
nicate with  cardiac  branches  of  the  sympathetic.  One  large 
branch  is  given  off  just  before  the  nerve  enters  the  chest;  on  the 
right  side  this  nerve  descends  by  the  side  of  the  arteria  innomi- 
nata  to  the  deep  cardiac  plexus ;  and  on  the  left  it  passes  in 
front  of  the  arch  of  the  aorta  to  the  superficial  cardiac  plexus. 

The  inferior  laryngeal,  or  recurrent  laryngeal  nerve,  curves 
around  the  subclavian  artery  on  the  right,  and  the  arch  of  the 
aorta  on  the  left  side.  It  ascends  in  the  groove  between  the 
trachea  and  oesophagus,  and  piercing  the  lower  fibres  of  the  in- 
ferior constrictor  muscle  enters  the  larynx  close  to  the  articula- 
tion of  the  inferior  cornu  of  the  thyroid  with  the  cricoid  cartilage. 
It  is  distributed  to  all  the  muscles  of  the  larynx,  with  the  excep- 
tion of  the  crico-thyroid,  and  communicates  on  the  arytenoideus 
muscle  with  the  superior  laryngeal  nerve.  As  it  curves  around 
the  subclavian  artery  and  aorta  it  gives  branches  (cardiac),  to 
the  heart  and  root  of  the  lungs  ;  and  as  it  ascends  the  neck  it 
distributes  filaments  to  the  oesophagus  and  trachea,  and  commu- 
nicates with  the  external  laryngeal  nerve  and  sympathetic. 

The  SPINAL  ACCESSORY  SWERVE,  in  its  passage  through  the  jugu- 
lar foramen,  is  contained  in  the  same  sheath  of  dura  mater  as  the 
pneumogastric  nerve,  and  is  applied  against  the  posterior  aspect 
of  its  superior  ganglion.  Quitting  the  opening  the  nerve  passes 
outwards  behind  and  sometimes  in  front  of  the  jugular  vein  to 
the  upper  part  of  the  sterno-mastoid  muscle,  whence  it  is  con- 
tinued obliquely  across  the  posterior  triangular  space  of  the  neck 
to  the  trapezius. 

The  branches  of  communication  of  the  spinal  accessory  are  one 
or  two  small  branches  from  the  superior  ganglion  of  the  pneumo- 


SYMPATHETIC   NERVE.  193 

gastric,  and  a  large  branch  which  joins  the  pneumogastric  be- 
tween the  two  ganglia. 

Its  branches  of  distribution  are  muscular  branches  to  the 
sterno-mastoid  and  trapezius. 

The  HYPOGLOSSAL  NERVE  [ninth]  passes  out  of  the  cranium 
through  the  anterior  condyloid  foramen,  where  it  is  situated  be- 
hind the  internal  carotid  artery  and  internal  jugular  vein;  it  then 
advances  forwards  between  the  artery  and  vein,  and  opposite  the 
angle  of  the  lower  jaw  curves  around  the  occipital  artery,  and 
crosses  the  external  carotid  artery  to  the  hyo-glossus  muscle. 
Resting  on  the  hyo-glossus  muscle  at  its  lower  part,  it  becomes 
flattened,  and  divides  into  a  number  of  branches  which  are  dis- 
tributed to  the  muscles  of  the  tongue. 

The  branches  of  communication  of  the  hypoglossal  nerve  are, 
several  to  the  pnoumogastric,  with  which  nerve  it  is  closely  united ; 
one  or  two  with  the  superior  cervical  ganglion  of  the  sympathetic ; 
and  one  or  two  with  the  loop  between  the  first  and  second  cervi- 
cal nerves. 

Its  branches  of  distribution  are  the  descendens  noni,  thyro- 
hyoidean,  and  muscular. 

The  descendens  noni  is  a  long  and  slender  nerve,  which  quits 
the  hypoglossal  just  as  it  is  about  to  form  its  arch  around  the 
occipital  artery,  and  descends  upon  the  sheath  of  the  carotid 
vessels.  Just  below  the  middle  of  the  neck,  it  forms  a  loop  with 
a  long  branch  from  the  second  and  third  cervical  nerves.  From 
the  convexity  of  this  loop  branches  are  sent  to  the  sterno-hyoideus, 
stiTiio-thyroideus,  and  both  bellies  of  the  omo-hyoideus ;  some- 
times also  a  twig  is  given  off  to  the  cardiac  plexus,  and  occasion- 
ally one  to  the  phrenic  nerve. 

The  thyro  hyoidean  nerve  is  a  small  branch  distributed  to  the 
thyro-hyoideus  muscle.  It  is  given  off  from  the  trunk  of  the 
hypoglossal  near  the  posterior  border  of  the  hyo-glossus  muscle, 
and  descends  obliquely  over  the  great  cornu  of  the  os  hyoides. 

The  muscular  branches  are  given  off  where  the  nerve  is  covered 
in  by  the  mylo-hyoideus  muscle,  and  rests  on  the  hyo-glossus ; 
several  large  branches  take  their  course  across  the  fibres  of  the 
genio-hyo-glossus  to  reach  the  substance  of  the  tongue.  More- 
over, on  the  hyo-glossus  muscle,  the  branches  of  the  hypoglossal 
nerve  communicate  with  those  of  the  gustatory  nerve. 

SYMPATHETIC  NERVE. 

The  sympathetic  nerve  is  brought  into  view  by  dividing  the  internal 
carotid  artery  and  internal  jugnlar  vein,  and  drawing  them  aside  together 
with  the  pneumogastric  nerve. 

The  cervical  portion  of  the  sympathetic  nerve  consists  of  three 
ganglia  with  their  connecting  cords  and  branches. 
17 


194 


THE   DISSECTOR. 


Fig.  57. 


The  SUPERIOR  CERVICAL  GANGLION  is  long  and  fusiform,  of  a 
reddish-gray  color,  smooth,  and  of  considerable  thickness,  extend- 
ing from  within  an  inch  of  the  carotid 
foramen  in  the  petrous  bone  to  opposite 
the  lower  border  of  the  third  cervical 
vertebra.  It  rests  on  the  rectus  anticus 
major  muscle,  and  lies  behind  and  to  the 
inner  side  of  the  internal  carotid  artery. 

Its  branches,  like  those  of  all  the  sym- 
pathetic ganglia  are  divisible  into  supe- 
rior, inferior,  external,  and  internal ;  to 
which  may  be  added,  as  proper  to  this 
ganglion,  anterior. 

The  superior  (carotid  nerve)  is  a  single 
branch  which  ascends  by  the  side  of  the 
internal  carotid,  and  divides  into  two 
branches ;  one  lying  to  the  outer,  the 
other  to  the  inner  side  of  that  vessel. 
The  two  branches  enter  the  carotid  canal, 
and  by  their  communications  with  each 
other,  and  with  the  petrosal  branch  of 
the  Yidian,  constitute  the  carotid  plexus. 
The  continuation  of  the  carotid  plexus 
onwards  with  the  artery  by  the  side  of 
the  sella  turcica  is  the  cavernous  plexus, 
and  from  the  latter  branches  having  a 
plexiform  distribution  are  given  off  with 
each  branch  of  the  artery. 

The  carotid  plexus,  moreover,  is  the 
means  of  communication  of  the  greater 
number  of  the  cranial  nerves  with  the 
rest  of  the  sympathetic.  It  sends  branches 
to  the  third  nerve,  the  ophthalmic,  the 
Casserian  ganglion  ;  two  large  branches 
join  the  sixth  nerve  in  the  cavernous 
sinus ;  it  sends  a  branch  to  the  ophthal- 

THE  SYMPATHETIC  NEUVE,  ITS  ENTIRE  LENGTH. — 1.  The  superior  cervical 

fanglion.  2.  Its  ascending  or  carotid  branch,  which  divides  into  two  branches. 
.  Its  descending  branch.  4.  Its  external  branches,  communicating  with  the 
first,  second,  and  third  cervical  nerves.  5.  Internal  branches  to  communicate 
with  the  facial  eighth  and  ninth  pairs,  and  with  the  pharyngeal  plexus.  6.  The 
superior  cardiac  nerve,  superficialis  cordis.  7.  The  middle  or  great  cardiac 
nerve,  arising  from  the  second  cervical  ganglion.  8.  The  inferior  cardiac  nerve, 
from  the  inferior  cervical  ganglion.  9.  The  first  dorsal  ganglion.  10.  The  last 
dorsal  ganglion.  11,11.  Spinal  nerves.  12.  Great  splanchnic  nerve.  13.  The 
two  semilunar  ganglia,  which  form  by  their  communications  the  solar  plexus. 
14.  The  lesser  splanchnic  nerve,  forming  the  renal  plexus.  15.  Branches  from 
the  lumbar  ganglia.  16.  The  hypogastric  plexus.  17.  Sacral  ganglia.  18.  The 
last  ganglion  or  the  sympathetic,  ganglion  impar. 


SYMPATHETIC   NERVE.  195 

mic  ganglion;  it  communicates  with  the  superior  maxillary,  the 
fat-in  1,  and  auditory  nerve  by  means  of  the  Vidian ;  with  the  in- 
ferior maxillary  by  a  branch  from  the  otic  ganglion;  and  with  the 
glosso-pharyugeal  by  means  of  two  filaments  to  the  tympanic 
nerve. 

The  inferior  or  descending  branch,  sometimes  two,  is  the  cord 
of  communication  with  the  middle  cervical  ganglion. 

The  external  branches  are  numerous,  and  may  be  divided  into 
two  sets  :  those  which  communicate  with  the  glosso-pharyngeal, 
pneumogastric,  and  hypoglossal  nerve ;  and  those  which  com- 
municate with  the  first  four  cervical  nerves. 

The  internal  branches  are  three  in  number :  pharyngeal,  to 
assist  in  forming  the  pharyngeal  plexus  ;  laryngeal,  to  join  the 
superior  laryngeal  nerve  and  its  branches  ;  and  the  superior 
cnrili  (ic  nerve,  or  nervus  superficialis  cordis. 

The  anterior  branches  accompany  the  external  carotid  artery 
with  its  branches,  around  which  they  form  plexuses,  and  here 
and  there  small  ganglia  ;  they  are  called,  from  the  softness  of 
their  texture,  nervi  molles,  and  from  their  reddish  hue,  nervi 
snhr-uji.  The  branches  accompanying  the  facial  artery  are  con- 
ducted by  that  vessel  to  the  submaxillary  ganglion,  and  those 
which  accompany  the  internal  maxillary  artery  reach  the  otic 
ganglion  through  the  medium  of  the  arteria  meningea  media. 

The  MIDDLE  CERVICAL  GANGLION  (thyroid  ganglion)  is  of  small 
size,  and  sometimes  altogether  wanting.  It  is  situated  opposite 
the  fifth  cervical  vertebra,  and  rests  against  the  inferior  thyroid 
artery.  This  relation  is  so  constant  as  to  have  induced  Haller 
to  name  it  the  "thyroid  ganglion." 

Its  superior  branch,  or  branches,  ascend  to  communicate  with 
the  superior  cervical  ganglion. 

Its  inferior  branches  descend  to  join  the  inferior  cervical  gan- 
glion ;  one  of  these  frequently  passes  in  front  of  the  subclavian 
artery,  the  other  behind  it. 

Its  external  branches  communicate  with  the  fifth  and  sixth 
cervical  nerves. 

Its  internal  branches  are  filaments  which  accompany  the  inferior 
thyroid  artery,  the  inferior  thyroid  plexus  ;  and  the  middle  cardiac 
nerve,  nervus  cardiacus  magnus. 

The  INFERIOR  CERVICAL  GANGLION  (vertebral  ganglion)  is  much 
larger  than  the  preceding,  and  is  constant  in  its  existence.  It  is 
of  a  semilunar  form,  and  is  situated  on  the  base  of  the  transverse 
process  of  the  seventh  cervical  vertebra  immediately  behind  the 
vertebral  artery;  hence  its  designation  "vertebral  ganglion." 

Its  superior  branches  communicate  with  the  middle  cervical 
ganglion. 


196  THE   DISSECTOR. 

The  inferior  branches  pass,  some  before  and  some  behind  the 
subclavian  artery,  to  join  the  first  thoracic  ganglion. 

The  external  branches  consist  of  two  sets  ;  one  which  commu- 
nicates witn  the  sixth,  seventh,  and  eighth  cervical  and  first  dorsal 
nerve,  and  one  which  accompanies  the  vertebral  artery  along  the 
vertebral  canal,  forming  the  vertebral  plexus.  This  plexus  sends 
filaments  to  all  the  branches  given  off  by  the  artery,  and  com- 
municates in  the  cranium  with  the  filaments  of  the  carotid  plexus 
accompanying  the  branches  of  the  internal  carotid  artery. 

The  internal  branch  is  the  inferior  cardiac  nerve,  nervus  car- 
diacus  minor. 

CARDIAC  NERVES. — The  cardiac  nerves  are  three  in  number  on 
each  side  of  the  neck ;  namely,  superior,  middle,  and  inferior. 

The  superior  cardiac  nerve  (nervus  superficial  cordis)  arises 
from  the  lower  part  of  the  superior  cervical  ganglion,  and  descends 
the  neck  behind  the  sheath  of  the  common  carotid  artery  to  the 
chest ;  crossing  in  its  course  the  inferior  thyroid  artery  and  recur- 
rent laryngeal  nerve.  The  nerve  of  the  left  side  follows  the  course 
of  the  carotid  artery,  and  crossing  the  arch  of  the  aorta  terminates 
in  the  superficial  cardiac  plexus.  The  nerve  of  the  right  side 
crosses  the  subclavian  artery  sometimes  in  front  and  sometimes 
behind,  and  follows  the  posterior  border  of  the  arteria  innominata 
to  the  deep  cardiac  plexus.  The  superficial  cardiac  nerve  receives 
filaments  from  the  pneumogastric  nerve,  and  distributes  branches 
to  the  thyroid  gland  and  trachea. 

The  middle  cardiac  nerve  (nervus  cardiacus  magnus)  proceeds 
from  the  middle  cervical  ganglion,  or,  in  its  absence,  from  the 
cord  of  communication  between  the  superior  and  inferior  ganglion. 
It  is  the  largest  of  the  three  nerves,  and  lies  parallel  with  the  re- 
current laryngeal.  At  the  root  of  the  neck  it  divides  into  several 
branches  which  pass,  some  before  and  some  behind,  the  subclavian 
artery,  communicates  with  the  superior  and  inferior  cardiac,  the 
pneumogastric,  and  recurrent  nerve,  and  descends  to  the  deep 
cardiac  plexus. 

The  inferior  cardiac  nerve  (nervus  cardiacus  minor)  arises  from 
the  inferior  cervical  ganglion,  communicates  with  the  recurrent 
laryngeal  and  middle  cardiac  nerve,  and  descends  to  the  deep 
cardiac  plexus. 

PR^EVERTEBRAL  REGION. 

The  student  should  now  cut  through  the  trachea  and  oesophagus,  with 
the  vessels  and  nerves  of  the  neck  opposite  the  first  rib,  and  draw  them 
forwards  ;  he  should  divide  with  the  scalpel  the  loose  cellular  tissue  which 
connects  the  back  part  of  the  pharynx  with  the  vertebral  column,  and 
continue  the  separation  to  the  base  of  the  skull.  He  should  then  make 
a  section  of  the  cranium  on  each  side  behind  the  mastoid  process,  direct- 
ing the  saw  towards  the  basilar  process,  and  then  break  through  the 


PR^EVERTEBRAL   REGION. 


m 


basilar  process  with  the  chisel  and  hammer, 
be  made  with  care,  and  the  eighth 
pair  of  nerves  at  their  exit  from  the 
cranium  as  much  as  possible  pre- 
served. Having  accomplished  this 
section,  he  may  proceed  to  examine 
the  muscles  lying  on  the  front  of  the 
vertebral  column  in  the  cervical 
region. 

The  muscles  of  the  praeverte- 
bral  region  are,  the  rectus  anti- 
cus  major  and  minor,  longus 
colli,  and  two  muscles  which 
have  been  already  examined, 
the  scaleni. 

The   RECTUS   ANTICUS  MAJOR, 

broad  and  thick  above,  and 
narrow  and  pointed  below, 
arises  from  the  anterior  tuber- 
cles of  the  transverse  processes 
of  the  third,  fourth,  fifth,  and 
sixth  cervical  vertebrae,  and  is 
inserted  into  the  basilar  process 
of  the  occipital  bone. 

The    RECTUS    ANTICUS    MINOR 

arises  from  the  anterior  border 
of  the  lateral  mass  of  the  atlas, 
and  is  inserted  into  the  basilar 


This  preparation  should 
Fig.  58. 


THE  PR^EVERTEBRAL  GROUP  OF 
MUSCLES  OP  THE  NECK. — 1.  The  rec- 
tus anticus  major  muscle.  2.  The  sca- 
lenus  anticus.  3.  The  lower  part  of  the 
longus  colli  of  the  right  side  ;  it  is  con- 


muscle.  6.  Its  lower  portion  ;  the  figure 
rests  upon  the  seventh  cervical  verte- 
bra. 7,  8.  The  scalenus  posticus.  9.  One 
of  the  inter-transversales  muscles.  10. 
The  rectus  lateralis  of  the  left  side. 


process,  its  fibres  being  directed  cea.led  superiorly  by  the  rectus  anticus 
*Y«.  j  j  .  ,  maior.  4.  The  rectus  anticus  minor. 

obliquely  upwards  and  inwards.   6<  JThe  upper  portion  Of  the  longus  colli 

The  LONGUS  COLLI  is  a  long 
and  flat  muscle,  consisting  of 
two  portions.  The  upper  arises 
from  the  anterior  tubercle  of  the 
atlas,  and  is  inserted  into  the 

transverse  processes  of  the  third,  fourth,  and  fifth  cervical  vertebrae. 
The  lower  portion  arises  from  the  bodies  of  the  second,  third, 
and  fourth,  and  transverse  processes  of  the  fifth  and  sixth,  and 
passes  down  the  neck,  to  be  inserted  into  the  bodies  of  the  three 
lower  cervical  and  three  upper  dorsal  vertebrae.  We  should  thus 
arrange  these  attachments  in  a  tabular  form  : — 

Origin.  Insertion. 

Upper)  ^tjas  f  3d,  4th,  and  5th  transverse 

portion  j  (      processes. 

Lower!  ^'  3(*'  an(*  4t^  Bodies  (  3  lower  cervical  vertebrae, 
portion  f     5lh  and  6th  trans-  ^      bodies 

)      verse  processes         ( 3  upper  dorsal,  bodies. 

17* 


198  THE   DISSECTOR. 

In  general  terms,  the  muscle  is  attached  to  the  bodies  and 
transverse  processes  of  the  six  superior  cervical  vertebrae  above, 
and  to  the  bodies  of  the  last  three  cervical  and  first  three  dorsal 
below. 

The  student  should  also  examine  in  this  region  the  rectus  late- 
ralis,  which  is  presented  by  its  anterior  face,  and  in  the  dissection 
of  the  back  was  seen  only  from  behind  ;  and  the  anterior  inter- 
transversales.  The  anterior  division  of  the  cervical  nerves  will 
be  found  between  the  anterior  and  posterior  inter-transversales. 

If  the  anterior  inter-transversales  be  removed,  the  vertebral 
artery  will  be  seen  taking  its  course  upwards  through  the  foramina 
in  the  transverse  processes  of  the  vertebra?.  It  lies  in  front  of 
the  cervical  nerves,  and  is  accompanied  by  the  vertebral  vein  and 
vertebral  plexus  of  nerves.  Opposite  each  inter-vertebral  foramen , 
the  vertebral  artery  sends  a  spinal  branch  into  the  vertebral  canal 
to  supply  the  spinal  cord. 

ACTIONS. — The  rectus  anticus  major  and  mi  nor  preserve  the  equilibrium 
of  the  head  upon  the  atlas  ;  and,  acting  conjointly  with  the  longus  colli, 
flex  and  rotate  the  head  and  the  cervical  portion  of  the  vertebral  column. 

ANATOMY  OF  THE  PHARYNX. 

Turning  now  to  the  portion  which  has  been  removed  from  the  front  of 
the  vertebral  column,  the  student  may  proceed  to  its  dissection.  By  the 
removal  of  the  cellular  tissue  from  the  nerves,  he  will  be  enabled  to  see 
the  communications  which  take  place  between  the  eighth  and  ninth  nerves 
and  sympathetic  ;  and  make  out  the  origin  of  the  upper  branches  of  the 
pneumogastric,  and  particularly  the  branches  distributed  to  the  pharynx 
and  larynx. 

Preparatory  to  dissecting  the  muscles  of  the  pharynx,  its  cavity  should 
be  distended  with  tow  or  wool.  The  students  should  then  remove  the 
cellular  tissue  from  off  the  muscles  on  one  side,  reserving  the  other  for 
the  examination  of  the  vessels  and  nerves. 

The  PHARYNX  is  a  musculo-membranous  sac  resting  against 
the  vertebral  column,  and  extending  from  the  base  of  the  skull 
to  opposite  the  cricoid  cartilage  and  fifth  cervical  vertebra.  It 
is  composed  of  muscles,  mucous  membrane,  and  a  strong  aponeu- 
rosis,  and  communicates  in  front  with  the  cavity  of  the  nose, 
mouth,  and  larynx.  Above  it  is  attached  partly  by  muscle,  but 
chiefly  by  aponeurosis,  to  the  basilar  process  of  the  occipital 
bone  and  petrous  portion  of  the  temporal,  and  below  it  is  con- 
tinous  with  the  oesophagus. 

The  MUSCLES  of  the  pharynx  are  the  superior,  middle,  and 
inferior  constrictor,  the  stylo-pharyngeus,  and  palato-pharyn- 
geus. 

The  CONSTRICTOR  INFERIOR,  the  thickest  of  the  three  muscles, 
arises  from  the  cricoid  cartilage  and  the  oblique  line  of  the  thy- 
roid. Its  fibres  spread  out  and  are  inserted  into  the  fibrous  raphe 


MUSCLES   OP  THE   PHARYNX. 


199 


of  the  middle  of  the  pharynx,  the  inferior  fibres  being  almost 
horizontal,  and  the  superior  oblique  and  overlapping  the  middle 
constrictor.  The  upper  border  of  the  muscle  is  in  relation  with 
the  superior  laryngeal  nerve,  and  the  lower  border  near  its  origin 
with  the  inferior  laryngeal  or  recurrent. 

Detach  the  upper  portion  of  the  inferior  constrictor  from  its  attachment 
to  the  raphe,  and  turn  it  downwards  to  bring  the  lower  part  of  the  next 
muscle  into  view. 

The  CONSTRICTOR  MEDIUS  arises  from  the  great  cornu  of  the  os 
hyoides,  from  the  lesser  cornu,  and  from  the  stylo-hyoidean  liga- 
ment. It  radiates,  from  its  origin,  upon  the  side  of  the  pharynx, 
the  lower  fibres  descending  and  being  overlapped  by  the  con- 
strictor inferior ;  and  the  upper  fibres  ascending,  so  as  to  cover 
in  the  constrictor  superior.  It  is  inserted  into  the  raphe,  and  by 
a  fibrous  aponeurosis  into  the  basilar  process  of  the  occipital 
bone.  The  lower  border  of  the  muscle  is  in  relation  with  the 
superior  laryngeal  nerve,  and  its  upper  border  is  separated  from 
the  superior  constrictor  by  the  stylo-pharyngeus  muscle  and 
glosso-pharyngeal  nerve. 

The  upper  portion  of  this  muscle  must  be  turned  down,  to  bring  the 
whole  of  the  superior  constrictor  into  view  ;  in  so  doing,  the  stylo-pha- 
ryngeus muscle  will  be  seen  passing  behind  its  upper  border. 

Fig.  59. 


A    SIDE    VIEW    OP     THE    MUSCLES    OF 

THK  PHAKYXX. — 1.  The  trachea.  2.  The 
cricoid  cartilage.  3.  The  erico-thyroid 
membrane.  4.  The  thyroid  cartilage. 
5.  The  thyro-hyoidean  membrane.  6. 
The  os  hyoides.  7.  The  stylo-hyoidean 
ligament.  8.  The  oesophagus.  9.  The 
inferior  constrictor.  10.  The  middle  con- 
strictor. 11.  The  superior  constrictor. 
12.  The  stylo-pharyngeus  muscle  passing 
down  between  the  superior  and  middle 
constrictor.  13.  The  upper  concave  bor- 
der of  the  superior  constrictor ;  at  this 
point  the  muscular  fibres  of  the  pharynx 
are  deficient.  14.  The  pterygo-maxillary 
liuMiiH-nt.  15.  The  buccinator  muscle. 
Hi.  The  orbicularis  oris.  17.  The  mylo- 
hyoideus. 


The  CONSTRICTOR  SUPERIOR  is  a  thin  and  quadrilateral  plane 
of  muscular  fibres,  arising  from  the  extremity  of  the  molar  ridge 
of  the  lower  jaw,  from  the  pterygo-maxillary  ligament,  and  from 
the  lower  third  of  the  internal  pterygoid  plate,  and  inserted  into 


200  THE   DISSECTOR. 

the  rapM  and  basilar  process  of  the  occipital  bone.  Its  superior 
fibres  are  arched,  and  leave  a  concave  interspace  between  its 
upper  border  and  the  basilar  process ;  some  of  its  lower  fibres 
are  continuous  with  those  of  the  genio-hyo-glossus  on  the  side  of 
the  tongue ;  and  it  is  overlapped  inferiorly  by  the  middle  con- 
strictor. 

Between  the  side  of  the  pharynx  and  the  ramus  of  the  lower  jaw  is  a 
triangular  interval,  the  maxillo-pharyngeal  space,  which  is  bounded  on  the 
inner  side  by  the  superior  constrictor  muscle ;  on  the  outer  side  by  the 
internal  pterygoid  muscle  ;  and  behind  by  the  rectus  anticus  major  and 
vertebral  column.  In  this  space  are  situated  the  internal  carotid  artery, 
the  internal  jugular  vein,  and  the  glosso-pharyngeal,  pneumogastric, 
spinal  accessory,  and  hypoglossal  nerve. 

The  STYLO-PHARYNGEUS  is  a  long  and  slender  muscle,  arising 
from  the  inner  side  of  the  base  of  the  styloid  process ;  it  descends 
between  the  superior  and  middle  constrictor  muscles,  and  spreads 
out  beneath  the  mucous  membrane  of  the  pharynx ;  it  is  inserted 
partly  into  the  posterior  border  of  the  thyroid  cartilage,  and 
partly  into  the  internal  face  of  the  inferior  constrictor.  Along 
its  lower  border  is  seen  the  glosso-pharyngeal  nerve  which  crosses 
it,  opposite  the  root  of  the  tongue,  to  pass  between  the  superior 
and  middle  constrictor  and  behind  the  hyo-glossus. 

When  the  muscles  of  the  exterior  of  the  pharynx  have  been  studied, 
the  sac  should  be  opened  along  the  middle  line,  and  the  sides  drawn 
apart  in  order  to  examine  its  interior. 

The  pharynx  presents  seven  openings,  two  at  its  upper  and 
front  part,  the  posterior  nares ;  one  on  each  side  of  the  posterior 
nares,  the  aperture  of  the  Eustachian  tube ;  below  the  posterior 
nares,  the  opening  of  the  mouth,  or  isthmus  faucium  ;  lower  down, 
the  opening  of  the  larynx  ;  and  inferiorly,  the  oesophagus. 

The  posterior  nares  are  oval  in  shape,  and  separated  from  each 
other  by  the  vomer. 

The  apertures  of  the  Eustachian  tubes  are  two  slit-like  open- 
ings, situated  one  at  each  side  of  the  fauces,  and  in  a  line  with 
the  posterior  extremity  of  the  inferior  spongy  bone.  The  Eus- 
tachian tube  is  a  fibro-cartilaginous  and  osseous  canal,  which 
extends  obliquely  outwards  and  upwards  to  the  tympanum,  and 
is  the  medium  of  communication  between  that  cavity  and  the 
external  air.  If  the  mucous  membrane  be  removed  from  around 
the  aperture,  the  fibro-cartilage  will  be  found  to  be  about  an 
inch  in  length,  broad  at  the  extremity,  and  narrower  as  it  pro- 
ceeds outwards.  It  is  lined  by  mucous  membrane  which  is  con- 
tinuous with  that  of  the  tympanum,  and  is  provided  around  the 
aperture  with  numerous  mucous  glands. 

Between  the  posterior  nares  and  the  opening  of  the  mouth  is  a 
rausculo-membranous  fold,  which  forms  a  kind  of  curtain  at  the 


SOFT   PALATE  —  TONSILS. 


201 


Fig.  60. 


back  of  the  mouth,  the  soft  palate  or  velum  pendulum  palati. 
Hanging  from  the  middle  of  its  inferior  border  is  a  small  rounded 
process,  the  uvula  ;  and  passing  outwards  from  the  uvula  on  each 
side  are  two  curved  folds  of  the 
mucous  membrane,  the  arches  or 
pillars  of  the  palate.  The  anterior 
pillar  is  continued  downwards  to 
the  side  of  the  base  of  the  tongue, 
and  is  formed  by  the  prominence 
of  the  palato-glossus  muscle.  The 
posterior  pillar  \&  prolonged  down- 
wards and  backwards  into  the 
pharynx,  and  is  formed  by  the 
convexity  of  the  palato-pharyn- 
geus  muscle.  These  two  pillars, 
closely  united  above,  are  sepa- 
rated below  by  a  triangular  inter- 
val or  niche,  in  which  the  tonsil 
is  lodged. 

The  TONSILS  (amygdalae)  are 
two  glandular  organs,  shaped  like 
almonds,  and  situated  between 
the  anterior  and  posterior  pillar 

of  the  Soft  palate,  On  each  Side  of    — 1.  The  basilar  process  of  the  occi 
the  fauces.       They   are    Composed     Ptal  bone.    2   2 The  petrous  portion 

of  an  assemblage  of  mucous  foi- 

licles,    wllk'll    Open  Upon  the    SUr- 

face  of  the  gland  by  about  twelve 
apertures.  Externally,  they  are 
invested  by  the  pharyngeal  fascia, 
which  separates  them  from  the  su- 
perior constrictor  muscle  and  in- 
ternal carotid  artery,  and  prevents 
an  abscess  from  opening  in  that 
direction.  In  relation  to  surrounding  parts,  each  gland  corre- 
sponds with  the  angle  of  the  lower  jaw. 

The  space  included  between  the  soft  palate  and  the  root  of  the 
tongue  is  the  isthmus  of  the  fauces.  It  is  bounded  above  by  the 
soft  palate,  on  each  side  by  the  pillars  of  the  soft  palate  and  ton- 
sils, and  below  by  the  root  of  the  tongue.  It  is  the  opening 
between  the  mouth  and  pharynx. 

The  opening  into  the  larynx  is  broad  in  front  and  narrow  be- 
hind. It  is  bounded  in  front  by  the  epiglottis,  and  on  the  sides 
by  the  fold  of  mucous  membrane  stretched  between  the  sides  of 
the  epiglottis  and  the  arytenoid  cartilages.  In  front  of  the  epi- 
glottis is  the  root  of  the  tongue. 


THE  OPENINGS  INTO  THE  PHARYNX. 


4,4.  The  openings  of  the  Eustachian 
tubes.  5.  Soft  palate.  6,  6.  The 
posterior  arches  of  the  soft  palate. 
7.  The  opening  from  the  mouth.  8. 
The  epiglottis.  9.  The  opening  into 
the  larynx.  10.  The  opening  into 
the  oesophagus.  11,  11.  The  sides 
of  the  pharynx  drawn  open.  12. 
The  oesophagus. 


202 


THE   DISSECTOR. 


The  opening  into  the  oesophagus  corresponding  with  the  lower 
border  of  the  inferior  constrictor  and  the  commencement  of  the 
circular  muscular  fibres,  has  the  appearance  of  the  aperture  of  a 
sphincter,  the  mucous  membrane,  paler  than  that  of  the  pharynx, 
being  thrown  into  folds. 

The  student  may  now  proceed  to  the  removal  of  the  mucous  membrane 
from  the  posterior  surface  and  pillars  of  the  palate,  and  for  some  little 
distance  on  the  side  of  the  pharynx.  On  the  middle  line  he  will  find  a 
pair  of  small  muscles  which  descend  into  the  uvula  ;  these  are  the  azygos 
uvulae.  On  the  side  of  the  soft  palate,  and  coming  down  from  the  base 
of  the  cranium,  is  the  levator  palati.  The  attachment  of  the  superior 
constrictor  to  the  internal  pterygoid  plate  should  now  be  defined  and 
divided  in  order  to  bring  into  view  a  muscle  which  lies  under  cover  of 
that  plate,  the  tensor  palati.  In  the  posterior  pillar  of  the  soft  palate  is 
the  palato-pharyngeus  muscle,  and  in  the  anterior  pillar  the  palato- 
glossus. 

The  MUSCLES  of  the  soft  palate  are — 

Levator  palati,  Azygos  uvulae, 

Tensor  palati,  Palato-glossus, 

Palato-pharyngeus. 

The  AZYGOS  UVULAE  is  a  pair  of  small  muscles  situated  along 
the  midline  of  the  soft  palate.  They  arise  from  the  spine  of  the 
palate  bone,  and  are  inserted  into  the  uvula. 

The  LEVATOR  PALATI  arises  from  the  extremity  of  the  petrous 
portion  of  the  temporal  bone,  and  from 
the  posterior  aspect  of  the  Eustachian 
tube,  and  passing  down  by  the  side  of 
the  posterior  naris,  spreads  out  between 
the  fasciculi  of  origin  of  the  palato-pha- 
ryngeus and  is  inserted  into  the  raphe, 
where  it  is  overlaid  bythe  azygos  uvulae. 
The  TENSOR  PALATI  (circumflexus), 
arises  from  the  scaphoid  fossa  at  the 
base  of  the  internal  pterygoid  plate, 
from  the  adjacent  part  of  the  sphenoid 
bone,  and  from  the  anterior  aspect  of 
the  Eustachian  tube.  It  lies  between 
the  internal  pterygoid  muscle  and  in- 
ternal pterygoid  plate,  and  winding 
around  the  hamular  process  of  the  lat- 

THE  PHARYNX  HAVING  BEEN  LAID  OPEN  FROM  BEHIND,  THE  CONSTRICTORS 
WERE  TURNED  OUTWARDS,  AND  THE  MUCOUS  MEMBRANE  WAS  REMOVED  FROM 
THEM  AND  FROM  THE  SOFT  PALATE.  THE  POSTERIOR  NARES,  THE  TONGUE, 
AND  THE  OPENING  INTO  THE  LARYNX  ARE  SEEN,  TOGETHER  WITH  THE  FOLLOW- 
ING MUSCLES,  viz  : — 1.  Levator  palati  mollis.  2.  Circumflexus  palati.  3. 
Azygos  uvulae.  4.  This  number  rests  on  the  tongue,-  it  points  to  the  palato- 
glossus.  5.  Palato-pharyngeus.  6.  Posterior  naris  of  one  side. 


Fig.  61, 


MUSCLES  OF   THE  PALATE.  203 

ter,  expands  into  a  tendinous  aponeurosis  which  is  inserted  into 
the  transverse  ridge  on  the  horizontal  portion  of  the  palate  bone 
and  into  the  raphe\ 

The  PALATO-PHARYNGEUS  forms  the  posterior  pillar  of  the 
fauces  ;  it  arises  by  two  fasciculi  from  the  raphe  of  the  soft 
palate,  where  its  fibres  are  continuous  with  those  of  the  muscle 
of  the  opposite  side ;  and  is  inserted  into  the  inner  surface  of 
the  pharynx  and  posterior  border  of  the  thyroid  cartilage.  This 
muscle  is  broad  above  where  it  forms  the  whole  thickness  of  the 
lower  half  of  the  soft  palate,  narrow  in  the  posterior  pillar,  and 
again  broad  and  thin  in  the  pharynx,  where  it  spreads  out  pre- 
viously to  its  insertion.  The  levator  palati  passes  to  its  insertion 
between  the  two  fasciculi  of  origin  of  the  muscle. 

The  PALATO-GLOSSUS  (constrictor  isthmi  faucium),  is  a  small 
fasciculus  of  fibres  which  arises  in  the  soft  palate,  and  descends 
to  be  inserted  into  the  side  of  the  tongue.  It  is  the  projection 
of  this  small  muscle,  covered  by  mucous  membrane,  that  forms 
the  anterior  pillar  of  the  soft  palate.  It  has  been  named  con- 
strictor isthmi  faucium,  from  a  function  it  performs  in  common 
with  the  palato-pharyngeus,  viz  :  of  constricting  the  opening  of 
the  fauces. 

ACTIONS. — The  azygos  uvulae  shortens  the  uvula.  The  levator  palati 
raises  the  soft  palate,  while  the  tensor  spreads  it  out  laterally  so  as  to 
form  a  septum  between  the  pharynx  and  posterior  nares.  Taking  its 
fixed  point  from  below,  the  tensor  palati  will  dilate  the  Eustachian  tube. 
The  palato-glossus  and  palato-pharyngeus  constrict  the  opening  of  the 
fauces,  and  by  drawing  down  the  soft  palate,  they  serve  to  press  the 
mass  of  food  from  the  dorsum  of  the  tongue  into  the  pharynx. 

The  (ESOPHAGUS  commences  at  the  lower  border  of  the  cricoid 
cartilage,  and  in  its  course  down  the  neck  rests  on  the  vertebral 
column,  inclining  to  the  left  so  as  to  project  beyond  the  border 
of  the  trachea  on  that  side.  It  is  composed  of  three  coats — 
muscular,  cellular,  and  mucous. 

The  muscular  coat  consists  of  two  layers  of  fibres,  of  which 
the  external  are  longitudinal,  and  the  internal  circular.  The 
longitudinal  fibres  commence  by  three  fasciculi,  anterior  and  two 
lateral:  the  anterior  fasciculus  is  attached  to  the  longitudinal 
ridge  on  the  posterior  surface  of  the  cricoid  cartilage;  the  lateral 
fasciculi  are  connected  with  the  inferior  constrictor  of  the  pha- 
rynx. The  internal  layer  of  circular  fibres  is  continuous  with  the 
inferior  constrictor. 

The  mucous  coat  is  covered  by  a  thick,  whitish  epithelium,  and 
is  thrown  into  longitudinal  folds. 

The  anatomy  of  the  nose,  mouth,  and  larynx  are  contained  in 
a  subsequent  chapter  (V.),  in  which  they  are  associated  with 
the  organs  of  vision  and  hearing. 


204  THE   DISSECTOR. 


CHAPTER   IT. 

BRAIN  AND  SPINAL  CORD. 

THE  brain  is  a  collective  term  which  signifies  those  parts  of  the 
nervous  system,  exclusive  of  the  nerves  themselves,  which  are 
contained  within  the  cranium:  they  are  the  cerebrum,  cerebellum, 
and  medulla  oblongata.  These  are  invested  and  protected  by 
the  membranes  of  the  brain,  and  the  whole  together  constitute 
the  encephalon  (lv  xf^a^,  within  the  head). 

To  examine  the  encephalon  with  its  membranes,  the  upper  part  of  the 
skull  must  he  removed  by  sawing  through  the  external  table,  and  break- 
ing the  internal  table  with  the  chisel  and  hammer.  After  the  calvaria 
has  been  loosened  all  round,  it  will  require  a  considerable  degree  of 
force  to  tear  the  bone  away  from  the  dura  mater.  This  adhesion  is  par- 
ticularly firm  at  the  sutures,  where  the  dura  mater  is  continuous  with  a 
membranous  layer  interposed  between  the  edges  of  the  bones ;  in  other 
situations,  the  connection  results  from  numerous  vessels  which  permeate 
the  inner  table  of  the  skull.  The  adhesion  subsisting  between  the  dura 
mater  and  bone  is  greater  in  the  young  subject  than  in  the  adult. 

Upon  being  torn  away,  the  internal  table  will  present  the  deeply 
grooved  and  ramified  channels  corresponding  with  branches  of  the 
arteria  meningea  media.  Along  the  middle  line  will  be  seen  a  groove 
corresponding  with  the  superior  longitudinal  sinus,  and  on  either  side 
may  be  frequently  observed  some  depressed  fossae,  corresponding  with 
the  Pacchionian  bodies. 

The  MEMBRANES  of  the  encephalon  and  spinal  cord  are  the 
dura  mater,  arachnoid  membrane,  and  pia  mater. 

The  DURA  MATER'  is  the  firm,  whitish  or  grayish  layer  which  is 
brought  into  view  when  the  calvaria  is  removed.  It  is  a  strong 
fibrous  membrane,  somewhat  laminated  in  texture,  and  composed 
of  white  fibrous  tissue.  Lining  the  interior  of  the  cranium,  it 
serves  as  the  internal  periosteum  of  that  cavity;  it  is  prolonged 
also  into  the  spinal  column,  under  the  name  of  theca  vertebralis, 
but  is  not  adherent  to  the  bones  in  that  canal  as  in  the  cranium. 
From  the  internal  surface  of  the  dura  mater,  processes  are 
directed  inwards  for  the  support  and  protection  of  parts  of  the 
brain;  while  from  its  exterior,  other  processes  are  prolonged 
outwards  to  form  sheaths  for  the  nerves  as  they  quit  the  skull 

1  So  named  from  a  supposition  that  it  was  the  source  of  all  the  fibrous 
membranes  of  the  body. 


GLANDULE   PACCHIONI.  205 

and  spinal  column.  Its  external  surface  is  rough  and  fibrous, 
and  corresponds  with  the  internal  table  of  the  skull.  The  inter- 
nal surface  is  smooth,  and  lined  by  the  thin  varnish-like  lamella 
of  the  arachnoid  membrane.  The  latter  is  a  serous  membrane. 
Hence  the  dura  mater  becomes  a  fibro-serous  membrane,  being 
composed  of  its  own  proper  fibrous  structure,  and  the  serous 
layer  derived  from  the  arachnoid.  There  are  two  other  instances 
of  fibro-serous  membrane  in  the  body,  formed  in  the  same  way, 
namely,  the  pericardium  and  tunica  albuginea  of  the  testicle. 

On  the  external  surface  of  the  dura  mater  the  branches  of  the  middle 
meningeal  artery  may  be  seen  ramifying ;  and  in  the  middle  line  is  a 
depressed  groove,  formed  by  the  subsidence  of  the  upper  wall  of  the  su- 
]><•!  ior  longitudinal  sinus.  If  the  sinus  be  opened  along  its  course,  it 
will  be  found  to  be  a  triangular  channel,  crossed  at  its  lower  angle  by 
numerous  white  bands,  called  chordae  Willisii;1  granular  bodies  are  also 
occasionally  seen  in  its  interior,  these  are  glandulse  Pacchioni. 

The  GLANDULE  PACCHIONI3  are  small,  round,  whitish  granula- 
tions, occurring  singly  or  in  clusters,  and  forming  small  groups 
of  various  size  along  the  margins  of  the  longitudinal  fissure  of 
the  cerebrum,  and  more  particularly  near  the  summit  of  the  latter. 
These  bodies  would  seem  to  be  of  morbid  origin;  they  are  absent 
in  infancy,  increase  in  numbers  in  adult  life,  and  are  abundant  in 
the  aged.  They  are  generally  associated  with  opacity  of  the 
arachnoid  around  their  bases,  but  in  some  instances  are  wanting 
even  in  the  adult.  They  have  their  point  of  attachment  in  the 
pia  mater,  from  which  they  seem  to  spring,  carrying  with  them 
the  arachnoid  membrane,  and  then,  in  proportion  to  their  size, 
producing  various  effects  upon  contiguous  parts.  For  example, 
when  small,  they  remain  free  or  constitute  a  bond  of  adhesion 
between  the  visceral  and  parietal  layer  of  the  arachnoid  :  when 
of  larger  size  they  produce  absorption  of  the  dura  mater,  and  as 
the  degree  of  absorption  is  greater  or  less,  they  protrude  through 
that  membrane,  and  form  depressions  on  the  inner  surface  of  the 
cranium,  or  simply  render  the  dura  mater  thin  and  cribriform. 
Sometimes  they  cause  absorption  of  the  wall  of  the  longitudinal 
sinus,  and  projecting  into  its  cavity,  give  rise  to  the  granulations 
described  in  connection  with  that  channel. 

[Hyrtl,  in  his  work  on  "  Topographical  Anatomy"  (Vienna, 
1853),  states  that  these  bodies  are  granular,  and  originate  from 
the  arachnoid;  and,  by  increase  in  size,  they  perforate  the  dura 

1  Willis  lived  in  the  seventeenth  century :  he  was  a  great  defender  of 
the  opinions  of  Harvey. 

2  These  bodies  are  incorrectly  described  as  conglobate  glands  by  Pac- 
chioni, in   an  epistolary  dissertation,  "De  Glandulis  conglobatis  Durae 
Mciiingis  indeque  ortis  Lymphaticis  ad  Piam  Matrem  productis,"  pub- 
lished at  Rome,  in  1705. 

18 


206  THE   DISSECTOR. 

mater,  then  enlarge  upon  the  outside  of  it,  and  thus  acquire  the 
shape  of  irregularly  round  masses,  with  contracted  necks  in  the 
centre.] 

If  the  student  cut  through  one  side  of  the  dura  mater,  in  the  direction 
of  his  incision  through  the  skull,  and  turn  it  upwards  towards  the  middle 
line,  he  will  observe  the  smooth  internal  surface  of  this  membrane.  He 
will  perceive  also  the  large  veins  of  the  hemispheres  filled  with  dark 
blood,  and  passing  from  behind  forwards  to  open  into  the  superior  longi- 
tudinal sinus  ;  and  the  firm  connection,  by  means  of  these  veins  and  the 
Pacchionian  bodies,  between  the  opposed  surfaces  of  the  arachnoid  mem- 
brane. If  he  separate  these  adhesions  with  his  scalpel,  he  will  see  a 
vertical  layer  of  dura  mater  descending  between  the  hemispheres  ;  and 
if  he  draw  one  side  of  the  brain  a  little  outwards,  he  will  be  enabled  to 
perceive  the  extent  of  the  process  of  membrane,  which  is  called  the  falx 
cerebri. 

The  processes  of  dura  mater  which  are  sent  inwards  towards 
the  interior  of  the  skull,  are  the  falx  cerebri,  tentorium  cerebelli , 
and  falx  cerebelli. 

The  falx  cerebri  (falx,  a  sickle),  so  named  from  its  sickle-like 
appearance,  narrow  in  front,  broad  behind,  and  forming  a  sharp 
curved  edge  below,  is  attached  in  front  to  the  crista  galli  process 
of  the  ethmoid  bone,  and  behind  to  the  tentorium  cerebelli. 

The  tentorium  cerebelli  (tentorium,  a  tent)  is  a  roof  of  dura 
mater,  thrown  across  the  cerebellum,  and  attached  at  each  side 
to  the  margin  of  the  petrous  portion  of  the  temporal  bone ; 
behind,  to  the  transverse  ridge  of  the  occipital  bone,  which  lodges 
the  lateral  sinuses ;  and  to  the  clinoid  processes  in  front.  It 
supports  the  posterior  lobes  of  the  cerebrum,  and  prevents  their 
pressure1  on  the  cerebellum,  leaving  only  a  small  opening  ante- 
riorly, for  the  transmission  of  the  crura  cerebri. 

The  falx  cerebelli  is  a  small  process,  generally  double,  attached 
to  the  vertical  ridge  of  the  occipital  bone  beneath  the  lateral 
sinus,  and  to  the  tentorium.  It  is  received  into  the  indentation 
between  the  two  hemispheres  of  the  cerebellum. 

The  student  cannot  see  the  tentorium  and  falx  cerebelli  until  the 
brain  is  removed  ;  but  he  should  consider  the  attachments  of  the  former 
on  the  dried  skull,  for  he  will  have  to  incise  it  in  the  removal  of  the 
brain.  He  should  now  proceed  to  that  operation,  for  which  purpose  the 
dura  mater  is  to  be  divided  all  round,  on  a  level  with  the  section  through 
the  skull,  and  the  scissors  are  to  be  carried  deeply  between  the  hemi- 
spheres of  the  brain  in  front  to  cut  through  the  anterior  part  of  the  falx  ; 
then  draw  the  dura  mater  backwards,  and  leave  it  hanging  by  its  attach- 
ment to  the  tentorium.  Raise  the  anterior  lobes  of  the  brain  carefully 
with  the  hand,  and  lift  the  olfactory  bulbs  from  the  cribriform  fossae  with 
the  handle  of  the  scalpel.  Then  cut  across  the  two  optic  nerves  and 
internal  carotid  arteries.  Next  divide  the  infundibulum  and  third 


1  In  leaping  animals,  as  the  feline  and  canine  genera,  the  tentorium 
forms  a  bony  tent. 


ARACHNOID   MEMBRANE.  20T 

nerves,  and  cany  the  knife  along  the  margin  of  the  petrous  bone  at  each 
side,  so  as  to  divide  the  tentorium  near  its  attachment.  Cut  across  the 
fourth,  fifth,  sixth,  seventh,  and  eighth  nerves  in  succession  with  a 
sharp  knife,  and  pass  the.  scalpel  as  far  down  as  possible  into  the  verte- 
bral canal,  to  sever  the  spinal  cord,  cutting  first  to  one  side  and  then  to 
the  other,  in  order  to  divide  the  vertebral  arteries  and  first  cervical 
nerves.  Then  let  him  press  the  cerebellum  gently  upwards  with  the 
fingers  of  the  right  hand,  the  hemispheres  being  supported  with  the  left, 
and  the  brain  will  roll  into  his  hand. 

The  student  may  now  direct  his  attention  to  the  anatomy  of  the  brain, 
and  the  two  membranes  which  form  its  immediate  investment ;  namely, 
the  ai-achnoid  and  pia  mater ;  leaving  the  dura  mater  in  the  base  of  the 
cranium,  the  exit  of  the  cranial  nerves,  and  the  sinuses  of  the  dura  mater 
for  subsequent  examination.  The  brain  should  be  placed  upon  a  plate, 
and  supported  by  a  towel,  disposed  like  a  turban  within  the  margin  of 
the  plate.  When  the  upper  surface  has  been  examined,  the  organ  should 
be  carefully  turned  in  order  to  display  the  under  surface  or  base. 

The  ARACHNOID  MEMBRANE  (dpa^vj?,  fl8os,  like  a  spider's  web), 
so  named  from  its  extreme  tenuity,  is  the  serous  membrane  of 
the  cerebro-spinal  centre  ;  and,  like  other  serous  membranes,  a 
shut  sac.  It  envelops  the  brain  and  spinal  cord  (visceral  layer), 
and  is  reflected  on  the  inner  surface  of  the  dura  mater  (parietal 
layer),  giving  to  that  membrane  its  serous  investment. 

On  the  upper  surface  of  the  hemispheres  the  arachnoid  is 
transparent,  but  may  be  demonstrated  as  it  passes  across  the 
sulci  from  one  convolution  to  another,  by  injecting  with  a  blow- 
pipe, a  stream  of  air  beneath  it.  At  the  base  of  the  brain  the 
membrane  is  opalescent  and  thicker  than  in  other  situations,  and 
more  easily  demonstrable  from  the  circumstance  of  stretching 
across  the  interval  between  the  middle  lobes  of  the  hemispheres. 
The  space  which  is  included  between  this  layer  of  membrane  and 
those  parts  of  the  base  of  the  brain  which  are  bounded  by  the 
optic  commissure  and  fissures  of  Sylvius  in  front,  and  the  pons 
Varolii  behind,  is  termed  the  anterior  sub-arachnoidean  space. 
Another  space  formed  in  a  similar  manner,  between  the  under 
part  of  the  cerebellum  and  the  medulla  oblongata,  is  the  posterior 
sub-arachnoidean  space;  and  a  third  space,  situated  over  the 
corpora  quadrigemina,  may  be  termed  the  superior  sub-arachnoi- 
dean space.  These  spaces  communicate  freely  with  each  other, 
the  anterior  and  posterior  across  the  crura  cerebelli,  the  anterior 
and  the  superior  around  the  crura  cerebri,  and  the  latter  and  the 
posterior  across  the  cerebellum  in  the  course  of  the  vermiform 
processes.  They  communicate  also  with  a  still  larger  space 
formed  by  the  loose  disposition  of  the  arachnoid  around  the 
spinal  cord,  the  spinal  sub-arachnoidean  space.  The  whole  of 
these  spaces,  with  the  lesser  spaces  between  the  convolutions  of 
the  hemispheres,  constitute  one  large  and  continuous  cavity, 
which  is  filled  with  a  limpid,  serous  secretion,  the  sub-arachnoi- 


208  THE   DISSECTOR. 

dean  or  cerebro-spinal  fluid,  a  fluid  which  is  necessary  to  the 
maintenance  and  protection  of  the  cerebro-spinal  mass.  The 
quantity  of  the  cerebro-spinal  fluid  is  determined  by  the  relative 
size  of  the  cerebro-spinal  axis  and  that  of  the  containing  cavity, 
and  is  consequently  very  variable.  It  is  smaller  in  youth  than  in 
old  age,  and  in  the  adult  has  been  estimated  at  about  two 
ounces.  The  visceral  layer  of  the  arachnoid  is  connected  to  the 
pia  mater  by  a  delicate  cellular  tissue,  which  in  the  sub-arach- 
noidean  spaces  is  loose  and  filamentous.  The  serous  secretion  of 
the  true  cavity  of  the  arachnoid  is  very  small  in  quantity  as  com- 
pared with  the  sub-arachnoidean  fluid. 

The  arachnoid  does  not  enter  into  the  ventricles  of  the  brain, 
as  imagined  by  Bichat,  but  is  reflected  inwards  upon  the  venae 
Galeni  for  a  short  distance  only,  and  returns  upon  those  vessels 
to  the  dura  mater  of  the  tentorium.  It  surrounds  the  nerves  as 
they  originate  from  the  brain,  and  forms  a  sheath  around  them 
to  their  point  of  exit  from  the  skull.  It  is  then  reflected  back 
upon  the  inner  surface  of  the  dura  mater. 

According  to  Mr.  Rainey,'  vessels  of  considerable  size,  but  few  in  num- 
ber, and  branches  of  cranial  nerves,  are  found  in  the  arachnoid.  He  also 
describes,  in  this  membrane,  numberless  plexuses  and  ganglia,  which  he 
considers  to  be  analogous  to  those  of  the  sympathetic  nerve.  The  fibres 
proceeding  from  this  source  are  distributed  on  the  arteries  and  nerves  of 
the  cerebro-spinal  axis,  but  particularly  on  the  former. 

The  PIA  MATER  is  a  vascular  membrane  composed  of  innume- 
rable vessels  held  together  by  a  thin  layer  of  cellular  tissue.  It 
invests  the  whole  surface  of  the  brain,  dipping  into  the  sulci 
between  the  convolutions,  and  forming  a  fold  in  its  interior 
called  velum  interpositum.  It  also  forms  folds  in  other  situa- 
tions, as  in  the  third  and  fourth  ventricles,  and  in  the  longitudi- 
nal fissures  of  the  spinal  cord. 

This  membrane  differs  in  structure  in  different  parts  of  the 
cerebro-spinal  axis.  Thus,  on  the  surface  of  the  cerebrum,  in 
contact  with  the  soft  gray  matter  of  the  brain,  it  is  extremely 
vascular,  forming  remarkable  loops  of  anastomoses  in  the  inter- 
spaces of  the  convolutions,  and  distributing  multitudes  of  minute 
straight  vessels  (tomentum  cerebri)  to  the  gray  substance.  In 
the  substantia  perforata,  again,  and  locus  perforatus,  it  gives  off 
tufts  of  small  arteries,  which  pierce  the  white  matter  to  reach  the 
gray  substance  in  the  interior.  But  upon  the  crura  cerebri,  pons 
Yarolii,  and  spinal  cord,  its  vascular  character  seems  almost  lost. 
It  has  become  a  dense  fibrous  membrane,  difficult  to  tear  off,  and 
forming  the  proper  sheath  of  the  spinal  cord. 

The  pia  mater  is  the  nutrient  membrane  of  the  brain,  and 

1  Medico-Chirurgical  Transactions,  vol.  xxix. 


INTERNAL  CAROTID  ARTERY. 


209 


derives  its  blood  from  the  internal  carotid  and  vertebral  arteries. 
Its  nerves  are  the  minute  filaments  of  the  sympathetic,  which 
accompany  the  branches  of  the  arteries.  At  the  base  of  the 
brain  the  arteries  maintain  a  remarkable  communication,  the 
circle  of  Willis.  If  the  arachnoid  membrane  be  removed,  and 
the  connections  of  the  pia  mater  gently  separated,  these  vessels 
may  be  examined. 

THE  CIRCLE  OF  WIL-  Fig.  62. 

LIS.  THE  BRANCHES  OP 
THE  ARTERIES  HAVE  RE- 
FERENCES ONLY  TO  ONE 
SIDE,  ON  ACCOUNT  OP 
THEIR  SYMMETRICAL 
DISTRIBUTION.  —  1.  The 
vertebral  arteries.  2. 
The  two  anterior  spinal 
branches  uniting  to  form 
a  single  vessel.  3.  One 
of  the  posterior  spinal 
arteries.  4.  The  poste- 
rior meningeal.  5.  The 
inferior  cerebellar.  6. 
The  basilar  artery  giv- 
ing off  its  transverse 
branches  to  either  side. 
7.  The  superior  cerebel- 


lar artery.  8.  The  pos- 
terior cerebral.  9.  The 
posterior  communicating 
branch  of  the  internal 
carotid.  10.  The  inter- 
nal carotid  artery,  show- 
ing the  curvatures  it 
makes  within  the  skull. 
11.  The  ophthalmic  arte- 
ry divided  across.  12. 
The  middle  cerebral  ar- 
tery. 13.  The  anterior  ce- 
rebral arteries  connect- 
ed by,  14.  The  anterior 
communicating  artery. 

The  INTERNAL  CAROTID  ARTERY  at  the  fissure  of  Sylvius  divides 
into  three  branches,  namely,  anterior  cerebral,  middle  cerebral, 
and  posterior  communicating. 

The  anterior  cerebral  artery  passes  forwards  in  the  great  longi- 
tudinal fissure  between  the  two  hemispheres  of  the  brain  ;  then 
curves  backwards  along  the  corpus  callosum  to  its  posterior  ex- 
tremity. It  gives  branches  to  the  olfactory  and  optic  nerves,  to 
the  under  surface  of  the  anterior  lobes,  the  third  ventricle,  the 
corpus  callosum,  and  the  inner  surface  of  the  hemispheres.  The 
two  anterior  cerebral  arteries  are  connected  soon  after  their  origin 
by  a  short  anastomosing  trunk,  the  anterior  communicating  artery. 

The  middle  cerebral  artery,  larger  than  the  preceding,  passes 

18* 


210  THE  DISSECTOR. 

outwards  along  the  fissure  of  Sylvius,  and  divides  into  three  prin- 
cipal branches,  which  supply  the  anterior  and  middle  lobes  of  the 
brain,  and  the  island  of  Reil.  Near  its  origin  it  gives  off  the 
numerous  small  branches  which  enter  the  substantia  perforata,  to 
be  distributed  to  the  corpus  striatum. 

The  posterior  communicating  artery,  very  variable  in  size, 
sometimes  double,  and  sometimes  altogether  absent,  passes  back- 
wards and  inosculates  with  the  posterior  cerebral,  a  branch  of 
the  basilar  artery.  Occasionally  it  is  so  large  as  to  take  the 
place  of  the  posterior  cerebral  artery. 

The  choroidean  artery  is  a  small  branch  given  off  by  the  in- 
ternal carotid,  near  the  origin  of  the  posterior  communicating  ; 
it  passes  beneath  the  edge  of  the  middle  lobe  of  the  brain  to  enter 
the  descending  cornu  of  the  lateral  ventricle,  and  is  distributed  to 
the  choroid  plexus. 

The  VERTEBRAL  ARTERY  pierces  the  dura  mater  on  the  side  of 
the  spinal  canal  between  the  atlas  and  occipital  bone,  and  enters 
the  cranium  through  the  foramen  magnum.  Opposite  the  lower 
border  of  the  pons  Varolii,  it  unites  with  its  fellow  of  the  opposite 
side  to  form  the  basilar  artery. 

The  BASILAR  ARTERY  passes  forwards,  resting  in  the  groove  on 
the  midline  of  the  pons  Yarolii ;  and  at  the  anterior  border  of  the 
pons  divides  into  four  ultimate  branches,  two  to  either  side. 

The  branches  of  the  vertebral  artery  within  the  cranium  and  of 
the  basilar  are  as  follows  : — 

Vertebral.  Basilar. 

Posterior  meningeal,  Inferior  cerebellar, 

Anterior  spinal,  Transverse, 

Posterior  spinal,  Superior  cerebellar, 

Posterior  cerebral. 

The  posterior  meningeal  are  one  or  two  small  branches  which 
enter  the  cranium  through  the  foramen  magnum,  to  be  distributed 
to  the  dura  mater  of  the  cerebellar  fossa?,  and  to  the  falx  cerebelli. 
One  branch,  described  by  Soemmering,  passes  into  the  cranium 
along  the  first  cervical  nerve. 

The  anterior  spinal  is  a  small  branch  which  unites  with  its  fellow 
of  the  opposite  side,  on  the  front  of  the  medulla  oblongata.  The 
artery  formed  by  the  union  of  these  two  vessels  descends  along 
the  anterior  aspect  of  the  spinal  cord,  to  which  it  distributes 
branches. 

The  posterior  spinal  winds  around  the  medulla  oblongata  to 
the  posterior  aspect  of  the  cord,  and  descends  on  either  side  to 
the  cauda  equina.  It  communicates  very  freely  with  the  spinal 
branches  of  the  intercostal  and  lumbar  arteries,  and  near  its  ori- 
gin sends  a  branch  upwards  to  the  fourth  ventricle. 


VEINS   OP  THE   BRAIN.  211 

The  inferior  cerebellar  arteries  wind  around  the  upper  part  of 
the  medulla  oblongata  to  the  under  surface  of  the  cerebellum,  to 
which  they  are  distributed.  They  pass  between  the  filaments  of 
origin  of  the  hypoglossal  nerve  in  their  course,  and  anastomose 
with  the  superior  cerebellar  arteries. 

The  transverse  branches  of  the  basilar  artery  supply  the  pons 
Yarolii,  and  adjacent  parts  of  the  brain.  One  of  these  branches, 
larger  than  the  rest,  passes  along  the  crus  cerebelli  to  be  distri- 
buted to  the  anterior  border  of  the  cerebellum  (middle  cerebellar 
artery). 

The  superior  cerebellar  arteries,  two  of  the  terminal  branches 
of  the  basilar,  wind  around  the  crus  cerebri  on  each  side,  lying 
in  relation  with  the  fourth  nerve,  and  are  distributed  to  the  upper 
surface  of  the  cerebellum,  inosculating  with  the  inferior  cerebellar. 
This  artery  gives  off  a  small  branch  (internal  auditory)  which 
accompanies  the  seventh  pair  of  nerves  into  the  meatus  auditorius 
internus  :  the  auditory  branch  may  be  derived  directly  from  the 
basilar. 

The  posterior  cerebral  arteries,  the  other  two  terminal  branches 
of  the  basilar,  wind  around  the  crus  cerebri  at' each  side,  and  are 
distributed  to  the  posterior  lobes  of  the  cerebrum.  They  are 
separated  from  the  superior  cerebellar  arteries,  near  their  origin, 
by  the  third  pair  of  nerves,  and  are  in  close  relation  with  the 
fourth  pair  in  their  course  around  the  crura  cerebri.  Anteriorly, 
near  their  origin,  they  give  off  a  tuft  of  small  vessels  which  enter 
the  locus  perforatus,  and  they  receive  the  posterior  communicating 
arteries  from  the  internal  carotid.  They  also  send  a  branch  to 
the  velum  interpositum  and  plexus  choroides,  posterior  choroid. 

The  communications  established  between  the  anterior  cerebral 
arteries  in  front,  and  the  internal  carotids  and  posterior  cerebral 
arteries  behind,  by  the  communicating  arteries,  constitute  the 
circle  of  Willis.  This  remarkable  vascular  communication  at  the 
base  of  the  brain  is  formed  by  the  anterior  communicating 
branch,  anterior  cerebrals,  and  internal  carotid  arteries  in  front, 
and  by  the  posterior  communicating,  posterior  cerebrals,  and 
basilar  artery  behind. 

The  VEINS  of  the  brain  are  also  situated  in  the  pia  mater,  and 
pour  their  contents  into  the  sinuses  of  the  dura  mater.  They 
are  remarkable  for  the  absence  of  valves  and  extreme  tenuity  of 
their  coats,  and  are  divisible  into  cerebral  and  cerebellar  veins, 
the  former  being  further  divided  into  superficial  and  deep. 

The  superficial  cerebral  veins  are  situated  on  the  surface  of  the 
hemispheres  lying  in  the  grooves  formed  by  the  convexities  of 
the  convolutions.  They  are  named,  from  the  position  which  they 
may  chance  to  occupy  upon  the  surface  of  the  organ,  either  su- 
perior or  inferior,  internal  or  external,  anterior  or  posterior. 


212  THE   DISSECTOR. 

The  superior  cerebral  veins,  seven  or  eight  in  number  on  each 
side,  pass  obliquely  forwards  and  terminate  in  the  superior  longi- 
tudinal sinus,  in  the  opposite  direction  to  the  course  of  the  stream 
of  blood  in  the  sinus. 

The  deep  or  ventricular  veins  commence  within  the  lateral  ven- 
tricles by  the  veins  of  the  corpora  striata  and  those  of  the  choroid 
plexus,  which  unite  to  form  the  vense  Galeni. 

The  vence  Galeni  pass  backwards  in  the  structure  of  the  velum 
interpositum,  and,  escaping  through  the  fissure  of  Bichat,  ter- 
minate in  the  straight  sinus. 

The  cerebellar  veins  are  disposed,  like  those  of  the  cerebrum, 
on  the  surface  of  the  lobes  of  the  cerebellum.  They  are  situated, 
some  upon  the  superior,  and  some  on  the  inferior  surface,  while 
others  occupy  the  borders  of  the  organ.  They  terminate  in  the 
lateral  and  petrosal  sinuses. 

CEREBRUM. 

The  cerebrum  presents  on  its  surface  a  number  of  slightly  con- 
vex elevations,  the  convolutions  (gyri),  which  are  separated 
from  each  other  by  sulci  of  various  depth.1  It  is  divided  supe- 
riorly into  two  hemispheres  by  the  great  longitudinal  fissure 
which  lodges  the  falx  cerebri,  and  marks  the  original  develop- 
ment of  the  brain  by  two  symmetrical  halves. 

Each  hemisphere,  upon  its  under  surface,  admits  of  a  division 
into  three  lobes — anterior,  middle,  and  posterior.  The  anterior 
lobe  rests  on  the  roof  of  the  orbit,  and  is  separated  from  the 
middle  by  the  fissure  of  Sylvius.3  The  middle  lobe  is  received 
into  the  middle  fossa  of  the  base  of  the  skull,  and  is  separated 
from  the  posterior  by  a  slight  impression  produced  by  the  ridge 
of  the  petrous  bone.  The  posterior  lobe  is  supported  by  the 
tentorium. 

If  the  upper  part  of  one  hemisphere,  at  about  one-third  from 
its  summit,  be  removed  with  a  scalpel,  a  centre  of  white  substance 
will  be  observed,  surrounded  by  a  narrow  border  of  gray,  which 
follows  the  line  of  the  sulci  and  convolutions,  and  presents  a 
zigzag  form.  This  section,  from  exhibiting  the  largest  surface 
of  medullary  substance  demonstrable  in  a  single  hemisphere,  is 
called  centrum  ovale  minus.  It  is  spotted  by  numerous  small 

1  In  estimating  the  surface  of  the  brain,  which,  according  to  Baillarger, 
averages  in  round  numbers  670  square  inches,  these  convolutions  and 
the  laminae  of  the  cerebellum  are  supposed  to  be  unfolded. 

2  James  Dubois,  a  celebrated  professor  of  anatomy  in  Paris,  where  he 
succeeded  Vidius  in  1550,  although  known  much  earlier  by  his  works  and 
discoveries,  but  particularly  by  his  violence  in  the  defence  of  Galen.  His 
name  was  Latinized  to  Sylvius. 


CEREBRUM.  213 

red  points  (puncta  vasculosa),  which  are  produced  by  the  escape 
of  blood  from  the  cut  ends  of  minute  arteries  and  veins. 

Separate  carefully  the  two  hemispheres  of  the  cerebrum,  and 
a  broad  band  of  white  substance  (corpus  callosum),  will  be  seen 
to  connect  them ;  it  will  be  seen  also  that  the  surface  of  the  he- 
misphere, where  it  comes  in  contact  with  the  corpus  callosum,  is 
bounded  bv^a  large  convolution  (gyrus  fornicatus),  which  lies 
horizontally  on  that  body,  and  may  be  traced  forwards  and 
backwards  to  the  base  of  the  brain,  terminating  by  each  extre- 
mity at  the  fissure  of  Sylvius.  The  sulcus  between  this  convo- 
lution and  the  corpus  callosum  has  been  termed,  very  improperly, 
the  "ventricle  of  the  corpus  callosum ;"  and  some  longitudinal 
fibres  (striae  longitudinales  laterales),  which  are  brought  into 
view  when  the  convolution  is  raised,  were  called  by  Reil  the 
"covered  band."  If  the  upper  part  of  each  hemisphere  be  re- 
moved to  a  level  with  the  corpus  callosum,  a  large  expanse  of 
medullary  matter,  surrounded  by  a  zigzag  line  of  gray  substance 
corresponding  with  the  convolutions  and  sulci  of  the  two  he- 
mispheres, will  be  seen.  This  is  the  centrum  ovale  majus  of 
Vieussens. 

The  corpus  callosum  (callosus,  hard)  is  a  thick  layer  of  medul- 
lary fibres  passing  transversely  between  the  two  hemispheres, 
and  constituting  the  great  commissure  (trabs  cerebri,  beam  of  the 
brain).  It  is  situated  in  the  middle  line  of  the  centrum  ovale 
majus,  but  nearer  the  anterior  than  the  posterior  part  of  the 
brain,  and  terminates  anteriorly  in  a  rounded  border  (genu), 
which  may  be  traced  downwards  to  the  base  of  the  brain  in  front 
of  the  commissure  of  the  optic  nerves.  Posteriorly  it  forms  a 
thick  rounded  fold  (splenium),  which  is  continuous  with  the  for- 
nix.  The  length  of  the  corpus  callosum  is  about  four  inches. 

Beneath  the  posterior  rounded  border  of  the  corpus  callosum 
is  the  transverse  Jlssure  of  the  cerebrum,  which  extends  between 
the  hemispheres  and  crura  cerebri  from  near  the  fissure  of  Syl- 
vius on  one  side,  to  the  same  point  on  the  opposite  side  of  the 
brain.  It  is  through  this  fissure  that  the  pia  mater  communicates 
with  the  velum  interpositum.  And  it  was  here  that  Bichat  con- 
ceived the  arachnoid  to  enter  the  ventricles;  hence  it  is  also 
named  ihejissure  of  Bichat. 

Along  the  middle  line  of  the  corpus  callosum  is  the  rapht,  a 
linear  depression  between  two  slightly  elevated  longitudinal 
bands  (chordae  longitudinales,  Lancisii)  ;  and,  on  either  side  of 
the  raphe,  may  be  seen  the  linece  transversee,  which  mark  the 
direction  of  the  fibres  of  which  the  corpus  callosum  is  composed. 
These  fibres  may  be  traced  into  the  hemispheres  on  either  side, 
and  they  will  be  seen  to  be  crossed  at  about  an  inch  from  the 
raphe  by  the  longitudinal  fibres  of  the  covered  band  of  Reil. 


214 


THE   DISSECTOR. 


Anteriorly  and  posteriorly  the  fibres  of  the  corpus  callosuin  curve 
into  their  corresponding  lobes. 

If  a  superficial  incision  be  made  through  the  corpus  callosum  on  either 
side  of  the  raphe,  two  irregular  cavities  will  be  opened,  which  extend 
from  one  extremity  of  the  hemispheres  to  the  other :  these  are  the  lateral 
ventricles.  To  expose  them  completely,  their  upper  boundary  should  be 
removed  with  the  scissors.  In  making  this  dissection,  the  thin  and 
diaphanous  membrane  of  the  ventricles  may  frequently  be  seen. 

LATERAL  VENTRICLES. — Each  lateral  ventricle  is  divided  into 
a  central  cavity,  and  three  smaller  cavities  called  cornua.  The 
anterior  cornu  curves  forwards  and  outwards  in  the  anterior  lobe; 
the  middle  cornu  descends  into  the  middle  lobe  ;  and  the  posterior 

Fig.  63. 

THE  LATERAL  VENTRICLES  OF 
THE  CEREBRUM. — 1,  1.  The  two 
hemispheres  cut  down  to  a  level 
with  the  corpus  callosum  so  as  to 
constitute  the  centrum  ovale  ma- 
jus.  The  surface  is  seen  to  be 
studded  with  the  small  vascular 
points — puncta  vasculosa ;  and  sur- 
rounded  by  a  narrow  margin  which 
represents  the  gray  substance.  2. 
A  small  portion  of  the  anterior 
extremity  of  the  corpus  callosum. 
3.  Its  posterior  boundary;  the  in- 
termediate portion  forming  the 
roof  of  the  lateral  ventricles  has 
been  removed,  so  as  to  completely 
expose  those  cavities.  4.  A  part 
of  the  septum  lucidum,  showing 
an  interspace  between  its  layers — 
the  fifth  ventricle.  5.  The  ante- 
rior cornu  of  one  side.  6.  The 
commencement  of  the  middle 
cornu.  7.  The  posterior  cornu. 
8.  The  corpus  striatum  of  one 
ventricle.  9.  The  tenia  semicir- 
cularis  covered  by  the  vena  cor- 

poris  striati  and  tenia  Tarini.  10.  A  small  part  of  the  Thalamus  opticus.  11. 
The  dark  fringe-like  body  to  the  left  of  the  figure  is  the  choroid  plexus.  This 
plexus  communicates  with  that  of  the  opposite  ventricle  through  the  foramen  of 
Munro ;  a  bristle  is  passed  through  this  opening,  and  its  extremities  are  seen 
resting  on  the  corpus  striatum  at  each  side.  The  figure  11  rests  upon  the  edge 
of  the  fornix,  upon  that  part  of  it  which  is  called  the  corpus  fimbriatum.  12. 
The  fornix.  13.  The  commencement  of  the  hippocampus  major  descending  into 
the  middle  cornu.  The  rounded  oblong  body  in  the  posterior  cornu  of  the 
lateral  ventricle,  directly  behind  the  figure  13,  is  the  hippocampus  minor. 

cornu  passes  backwards  in  the  posterior  lobe,  converging  towards 
its  fellow  of  the  opposite  side.  The  central  cavity  is  triangular 
in  form,  being  bounded  above  (roof)  by  the  corpus  callosum  ; 
internally  by  the  septum  lucidum,  which  separates  it  from  the 


CHOBOID  PLEXUS.  215 

opposite  ventricle ;  and  below  (floor)  by  the  following  parts, 
taken  in  their  order  of  position  from  before  backwards  : — 
Corpus  striatum,  Choroid  plexus, 

Tenia  semicircularis,          Corpus  fimbriatum, 
Thalaraus  opticus,  Fornix. 

The  corpus  striatum  is  named  from  the  striated  lines  of  white 
and  gray  matter  which  are  seen  upon  cutting  into  its  substance. 
It  is  gray  on  the  exterior,  and  of  a  pyriform  shape.  The  broad 
end,  directed  forwards,  rests  against  the  corpus  striatum  of  the 
opposite  side :  the  small  end,  backwards,  is  separated  from  its 
fellow  by  the  interposition  of  the  thalami  optici.  The  corpora 
striata  are  the  superior  ganglia  of  the  cerebrum. 

The  tenia  semicircularis  (tenia,  a  fillet)  is  a  narrow  band  of 
medullary  substance,  extending  along  the  posterior  border  of  the 
corpus  striatum,  and  serving  as  a  bond  of  connection  between 
that  body  and  the  thalamus  opticus.  It  is  transparent  and  dense 
at  the  surface,  and  received  from  Tarinus1  the  name  of  horny 
band.  The  tenia  is  partly  concealed  by  a  large  vein  (vena  cor- 
poris  stridti),  which  receives  numerous  small  veins  from  the 
corpus  striatum  and  thalamus  opticus,  and  terminates  in  the 
vena  Galeni  of  its  own  side. 

The  thalamus  opticus  (thalamus,  a  bed)  is  an  oblong  body, 
having  a  thin  coating  of  white  substance  on  its  surface ;  it  has 
received  its  name  from  giving  origin  to  one  root  of  the  optic  nerve. 
It  is  the  inferior  ganglion  of  the  cerebrum.  Part  only  of  the 
thalamus  is  seen  in  the  floor  of  the  lateral  ventricle ;  we  must 
therefore  defer  its  further  description  until  we  can  examine  it  in 
its  entire  extent. 

The  choroid plexus  (^opiov,  tl&o$,  resembling  the  chorion3)  is  a 
vascular  fringe  extending  obliquely  across  the  floor  of  the  lateral 
ventricle,  and  sinking  into  the  middle  cornu.  Anteriorly,  it  is 
small  and  tapering,  and  communicates  with  the  choroid  plexus  of 
the  opposite  ventricle,  through  a  large  oval  opening,  the  foramen 
of  Monro,  or  foramen  commune  anterius.  This  foramen  may  be 
distinctly,  seen  by  pulling  slightly  on  the  plexus,  and  pressing 
aside  the  septum  lucidum  with  the  handle  of  the  knife.  It  is 
situated  between  the  under  surface  of  the  fornix  and  the  anterior 
extremities  of  the  thalami  optici,  and  forms  a  communication 
transversely  between  the  lateral  ventricles,  and  perpendicularly 
with  the  third  ventricle. 

1  Fetor  Tarin,  a  French  anatomist:  his  work,  entitled  "Adversaria 
Anatomica,"  was  published  in  1750. 

1  See  the  note  appended  to  the  description  of  the  choroid  coat  of  the 
eyeball. 


216 


THE   DISSECTOR. 


The  choroid  plexus  presents  upon  its  surface  a  number  of  minute  vas- 
cular processes,  which  are  termed  villi.  They  are  invested  by  a  very 
delicate  epithelium,  surmounted  by  cilia,  which  have  been  seen  in  active 
movement  in  the  embryo.  In  their  interior  the  plexuses  not  unfrequently 
contain  particles  of  calcareous  matter,  and  are  sometimes  covered  by  small 
clusters  of  serous  cysts. 

Fig.  64. 


A  DIAGRAM,  REPRESENTING  A  TRANSVERSE  SECTION  OF  THE  BRAIN.—!,  1. 
The  corpus  callosum,  or  great  commissure  of  the  hemispheres,  extending  trans- 
versely into  each  hemisphere.  2.  The  raphe,  a  linear  depression  between  two 
slightly  elevated  ridges.  3,  3.  The  lateral  ventricles.  4.  The  space  between 
the  two  layers  of  the  septum  luciduni,  called  the  fifth  ventricle.  5,  5.  The 
fornix.  6,  6.  The  thin  edges  of  the  fornix,  called  corpora  fimbriata.  7.  The 
velum  interpositum.  8,  8.  The  plexiform  borders  of  the  velum  interpositum, 
called  choroid  plexuses.  9,  9.  The  thalami  optici.  10.  The  space  between  the 
two  thalami,  called  third  vent.ricle.  11.  The  gray  commissure  of  the  thalami 
optici,  called  middle  commissure,  or  cominissura  mollis  of  the  third  ventricle. 
12.  The  line  of  the  base  of  the  brain. 

The  corpus  finibriatum  is  a  narrow  white  band,  situated  imme- 
diately behind  the  ehoroid  plexus,  and  extending  with  it  into  the 
descending  cornu  of  the  lateral  ventricle.  It  is,  in  fact,  the  lateral 
thin  edge  of  the  fornix,  and  being  attached  to  the  hippocampus 
major  in  the  descending  horn  of  the  lateral  ventricle,  it  is  also 
termed  tenia  hippocampi. 

Theybrmx  is  a  white  layer  of  medullary  substance,  of  which  a 
portion  only  is  seen  in  this  view  of  the  ventricle. 

The  anterior  cornu  is  triangular  in  its  form,  sweeping'outwards, 
and  terminating  by  a  point  in  the  anterior  lobe  of  the  brain,  at  a 
short  distance  from  its  surface. 

The  posterior  cornu  or  digital  cavity  curves  inwards,  as  it  ex- 
tends back  into  the  posterior  lobe  of  the  brain,  and  likewise  ter- 
minates near  the  surface.  An  elevation  (corresponding  with  a 
deep  sulcus  between  two  convolutions)  projects  into  the  area  of 
this  cornu,  and  is  called  the  hippocampus  minor. 

The  middle  or  descending  cornu,  in  descending  into  the  middle 
lobe  of  the  brain,  forms  a  very  considerable  curve,  and  alters  its 
direction  several  times  as  it  proceeds.  Hence  it  is  described  as 


HIPPOCAMPUS  MAJOE.  21f 

passing  backwards  and  outwards  and  downwards,  and  then  turn- 
ing forwards  and  inwards.1  It  is  the  largest  of  the  three  cornua, 
and  terminates  close  to  the  fissure  of  Sylvius,  after  having  curved 
around  the  crus  cerebri. 

The  middle  cornu  should  now  be  laid  open,  by  inserting  the  little  fin- 
ger into  its  cavity,  and  making  it  serve  as  a  director  for  the  scalpel  in 
cutting  away  the  side  of  the  hemisphere,  so  as  to  expose  it  com- 
pletely. 

The  superior  boundary  of  the  middle  cornu  is  formed  by  the 
under  surface  of  the  thalamus  opticus,  upon  which  are  the  two 
projections  called  corpus  geniculatum  internum  and  externum ; 
and  the  inferior  wall  by  the  following  parts  : — 

Hippocampus  major,  Choroid  plexus, 

Pes  hippocampi,  Fascia  dentata, 

Pes  accessorius,  Transverse  fissure. 

Corpus  fimbriatum, 

The  hippocampus  major  or  cornu  Ammonis,  so  called  from  its 
resemblance  to  a  ram's  horn,  the  famous  crest  of  Jupiter  Ammon, 
is  a  considerable  projection  from  the  inferior  wall,  and  extends 
the  whole  length  of  the  middle  cornu.  Its  extremity  is  likened 
to  the  foot  of  an  animal,  from  its  presenting  a  number  of  knuckle- 
like  elevations  upon  the  surface,  and  is  named  pes  hippocampi. 
The  hippocampus  major  is  the  internal  surface  of  the  convolu- 
tion (gyrus  fornicatus),  of  the  lateral  edge  of  the  hemisphere, 
the  convolution  which  has  been  previously  described  as  lying 
upon  the  corpus  callosum  and  extending  downwards  to  the  base 
of  the  brain  to  terminate  at  the  fissure  of  Sylvius.  If  it  be 
cut  across,  the  section  will  be  seen  to  resemble  the  extremity 
of  a  convoluted  scroll,  consisting  of  alternate  layers  of  white  and 
gray  substance.  The  hippocampus  major  is  continuous  superiorly 
with  the  fornix  and  corpus  callosum,  and  derives  its  medullary 
layer  from  the  corpus  fimbriatum. 

The  pes  accessorius  (eminentia  collaterals),  is  a  swelling  some- 
what resembling  the  hippocampus  major,  but  smaller  in  size,  and 
situated  in  the  angular  interval  between  it  and  the  hippocampus 
minor.  Like  the  latter,  it  is  formed  by  the  protrusion  of  one  of 
the  sulci  of  the  convolutions. 

The  corpus  fimbriatum  (tenia  hippocampi),  is  the  narrow 
white  band  which  is  prolonged  from  the  central  cavity  of  the 
ventricle,  and  is  attached  along  the  inner  border  of  the  hippo- 
campus major.  It  is  lost  inferiorly  on  the  hippocampus. 

1  This  complex  expression  of  a  very  simple  curve  has  given  origin  to 
a  symbol  formed  by  the  primary  letters  of  these  various  terms  ;  and  by 
means  of  this  the  student  recollects  with  ease  the  course  of  the  cornu, 
BODFI. 
19 


218  THE   DISSECTOR. 

Fascia  dentata. — If  the  corpus  fimbriatum  be  carefully  raised, 
a  narrow  serrated  band  of  gray  substance,  the  margin  of  the 
gray  substance  of  the  middle  lobe  will  be  seen  beneath  it;  this 
is  the  fascia  dentata.  Beneath  the  corpus  fimbriatum  will  be 
likewise  seen  the  transverse  fissure  of  the  brain,  which  has  been 
before  described  as  extending  from  near  the  fissure  of  Sylvius  on 
one  side,  across  to  the  same  point  on  the  opposite  side  of  the 
brain.  It  is  through  this  fissure  that  the  pia  mater  communi- 
cates with  the  choroid  plexus,  and  the  latter  obtains  its  supply 
of  blood.  The  fissure  is  bounded  on  one  side  by  the  corpus 
fimbriatum,  and  on  the  other  by  the  under  surface  of  the  thala- 
mus  opticus. 

The  internal  boundary  of  the  lateral  ventricle  is  the  septum 
lucidum.  This  septum  is  thin  and  semi-transparent,  and  consists 
of  two  laminae  of  cerebral  substance  attached  above  to  the  under 
surface  of  the  corpus  callosum  at  its  anterior  part,  and  below 
to  the  fornix.  Between  the  two  layers  is  a  narrow  space,  the 
fifth  ventricle,  which  is  lined  by  a  proper  membrane.  The  fifth 
ventricle  may  be  shown,  by  snipping  through  the  septum  lucidum 
transversely  with  the  scissors. 

The  corpus  callosum  should  now  be  cut  across  towards  its  anterior 
extremity,  and  the  two  ends  carefully  dissected  away.  The  anterior 
portion  will  be  retained  only  by  the  septum  lucidum,  but  the  posterior 
will  be  found  incorporated  with  the  white  layer,  beneath  which  is  the 
fornix. 

FORNIX. — The  fornix  (arch),  is  a  triangular  lamina  of  white 
substance,  broad  behind,  and  extending  into  each  lateral  ven- 
tricle :  narrow  in  front,  where  it  terminates  in  two  crura,  which 
arch  downwards  to  the  base  of  the  brain.  The  two  crura  de- 
scend in  a  curved  direction  to  the  base  of  the  brain,  embedded 
in  gray  substance  in  the  lateral  walls  of  the  third  ventricle,  and 
lying  directly  behind  the  anterior  commissure.  At  the  base  of 
the  brain  they  make  a  sudden  curve  upon  themselves  and  consti- 
tute the  corpora  albicantia,  from  which  they  may  be  traced  up- 
wards to  their  origin  in  the  thalami  optici.  Opening  transversely 
beneath  these  two  crura,  just  as  they  are  about  to  arch  down- 
wards, is  the  foramen  of  communication  between  the  lateral  and 
the  third  ventricle,  the  foramen  ofMonro  ;  or  foramen  commune 
anterius.  The  choroid  plexuses  communicate,  and  the  veins  of 
the  corpora  striata  pass  through  this  opening. 

The  lateral  thin  edges  of  the  fornix  are  continuous  posteriorly 
with  the  concave  border  of  the  hippocampus  major  at  each  side, 
and  form  the  narrow  white  band  called  corpus  fimbriatum  (pos- 
terior cms  of  the  fornix).  In  the  middle  line  the  fornix  is  con- 
tinuous with  the  corpus  callosum,  and  at  each  side  with  the 
hippocampus  major  and  minor.  Upon  the  under  surface  of  the 


FORNIX. 


219 


fornix  towards  its  posterior  part,  some  transverse  lines  are  seen 
passing  between  the  diverging. corpora  fimbriata:  this  appear- 

Fig.  65. 


A  DIAGRAM   REPRESENTING    THE    LONGITUDINAL     SECTION    OP     THE     BRAIN 

BETWEEN  THE  TWO  HEMISPHERES. — 1.  The  corpus  callosum.  2.  Its  anterior 
extremity  turning  downwards  to  terminate  at  the  base  of  the  brain.  3.  Its 
posterior  extremity,  much  larger  than  the  anterior,  forms  a  rounded  border, 
which  is  continuous  with  4.  The  fornix.  5.  The  two  crura  of  the  fornix,  ter- 
minating in  6.  The  two  corpora  albicantia.  7.  The  septum  lucidum.  8.  The 
velum  interpositum.  9.  The  foramen  of  Munro.  10.  The  venae  Galeni,  escap- 
ing through  the  fissure  of  BichSt  to  enter  the  straight  sinus.  11.  The  third 
ventricle.  12.  Section  of  the  anterior  commissure.  13.  Section  of  the  middle 
commissure,  cominissura  mollis.  14.  Section  of  the  posterior  commissure. 
15.  The  foramen  commune  anterius,  or  space  between  the  anterior  and  middle 
commissure,  leading  downwards  in  the  direction  of  the  arrow,  between  the 
crura  of  the  fornix  to  the  infundibulum  :  hence  it  is  also  named  iter  ad  infundi- 
Imlum.  16.  The  pituitary  gland.  17.  The  foramen  commune  posterius.  18. 
The  cut  edge  of  the  corpora  quadrigemina,  which  forms  the  superior  boundary 
of  the  iter  i  tertio  ad  quartum  ventriculum,  leading  from  the  third  (11.)  into 
the  fourth  ventricle  19.  20.  The  corpora  quadrigemina.  21.  The  crus  cerebri 
of  the  right  side.  22.  Section  of  the  pons  Varolii.  23.  Section  of  the  medulla 
oblongata. 

ance  is  termed  the  lyra  (corpns  psalloides),  from  a  fancied  re- 
semblance to  the  strings  of  a  harp. 

Tim  fornix  may  now  be  removed  by  dividing  it  across  anteriorly  and 
turning  it  backwards,  at  the  same  time  separating  its  lateral  connec- 
tions with  the  hippocampi.  If  the  student  examine  its  under  surface, 
he  will  perceive  the  lyra  above  described. 

Beneath  the  fornix  is  the  velum  interpositum  (tela  choroidea), 
a  duplicature  of  pia  mater  introduced  into  the  interior  of  the 
brain,  through  the  transverse  fissure.  The  velum  is  continuous 
at  each  side  with  the  choroid  plexus,  and  contains  in  its  inferior 
layer  two  large  veins  (yence  Galeni)  which  receive  the  blood 


220  THE   DtSSECTOR. 

from  the  corpora  striata  and  choroid  plexuses,  and  terminate 
posteriorly,  after  uniting  into  a  single  trunk,  in  the  straight 
sinus.  Upon  the  under  surface  of  the  velum  interpositum  are 
two  fringe-like  bodies,  which  project  into  the  third  ventricle. 
These  are  the  choroid  plexuses  of  the  third  ventricle;  posteriorly 
these  fringes  inclose  the  pineal  gland. 

If  the  velum  interposition  be  raised  and  turned  back,  an  operation 
which  must  be  conducted  with  care,  particularly  at  its  posterior  part 
where  it  invests  the  pineal  gland,  the  thalami  optici  and  the  cavity  of 
the  third  ventricle  will  be  brought  into  view. 


THE  MESIAL  SURFACE  OP  A  LONGITUDINAL  SECTION  OF  THE  BRAIN.     THE 

INCISION  HAS  BEEN  CARRIED  ALONG  THE  MIDDLE  LINE  ;  BETWEEN  THE  TWO 
HEMISPHERES  OF  THE  CEREBRUM,  AND  THROUGH  THE  MIDDLE  OF  THE  CERE- 
BELLUM AND  MEDULLA  OBLONGATA. — 1.  The  inner  surface  of  the  left  hemi- 
sphere. 2.  The  divided  surface  of  the  cerebellum,  showing  the  arbor  vita?. 
3.  The  medulla  oblongata.  4.  The  corpus  callosum,  rounded  before  to  termi- 
nate in  the  base  of  the  brain ;  and  behind,  to  become  continuous  with  5,  the 
fornix.  6.  One  of  the  crura  of  the  fornix  descending  to  7,  one  of  the  corpora 
albicantia.  8.  The  septum  lucidum.  9.  The  velum  interpositum,  communi 
eating  with  the  pia  mater  of  the  convolutions  through  the  fissure  of  Bichat. 
10.  Section  of  the  middle  commissure  situated  in  the  third  ventricle.  11.  Sec- 
tion of  the  anterior  commissure.  12.  Section  of  the  posterior  commissure  ;  the 
commissure  is  somewhat  above  and  to  the  left  of  the  number.  The  interspace 
between  10  and  11  is  the  foramen  commune  anterius,  in  which  the  crus  of  the 
fornix  (6)  is  situated.  The  interspace  between  10  and  12  is  the  foramen  com- 
mune posterius.  13.  The  corpora  quadrigeinina,  upon  which  is  seen  resting 
the  pineal  gland,  14.  15.  The  iter  a  tertio  ad  quartum  ventriculum.  16.  The 
fourth  ventricle.  17.  The  pons  Varolii,  through  which  are  seen  passing  the 
diverging  fibres  of  the  corpora  pyramidalia.  18.  The  crus  cerebri  of  the  left 
side,  with  the  third  nerve  arising  from  it.  19.  The  tuber  cinereum,  from 
which  projects  the  infundibulum,  having  the  pituitary  gland  appended  to  its 
extremity.  20.  One  of  the  optic  nerves.  21.  The  left  olfactory  nerve  termi- 
nating anteriorly  in  a  rounded  bulb. 

THALAMI  OPTICI. — The  thalami  optici  are  two  oblong,  square- 
shaped  bodies,  of  a  white  color  superficially,  inserted  between 
the  two  diverging  portions  of  the  corpora  striata.  In  the  mid- 


THIRD   VENTRICLE.  221 

die  line  a  fissure  exists  between  them  which  is  called  the  third 
ventricle.  Posteriorly  and  inferiorly,  they  form  the  superior  wall 
of  the  descending  cornu  of  the  lateral  ventricle,  and  present  two 
rounded  elevations  called  corpus  geniculatum  extemiim  and  in- 
ternum.  The  corpus  geniculatum  extemum  is  the  larger  of  the 
two,  and  of  a  grayish  color ;  it  is  the  principal  origin  of  the 
optic  nerve.  Anteriorly,  the  thalami  are  connected  with  the 
corpora  albicantia  by  means  of  two  white  bands,  which  appear 
to  originate  in  the  white  substance  (tenia  semicircularius)  uniting 
the  thalami  to  the  corpora  striata.  Externally  they  are  in  rela- 
tion with  the  corpora  striata  and  hemispheres.  In  their  interior 
the  thalami  are  composed  of  white  fibres  mixed  with  gray  sub- 
stance. They  are  essentially  the  inferior  ganglia  of  the  cerebrum. 

THIRD  VENTRICLE. — The  third  ventricle  is  the  fissure  between 
the  two  thalami  optici.  It  is  bounded  above  by  the  under  surface 
of  the  velum  interpositum,  from  which  are  suspended  the  choroid 
plexuses  of  the  third  ventricle.  Its  floor  is  formed  by  the  gray 
substance  of  the  anterior  termination  of  the  corpus  callosum,  called 
lamina  cinerea,  the  tuber  cinereum,  corpora  albicantia,  and  locus 
perforatus.  Laterally  it  is  bounded  by  the  thalami  optici ;  an- 
teriorly by  the  anterior  commissure  and  crura  of  the  fornix  ;  and 
posteriorly  by  the  posterior  commissure  and  the  iter  a  tertio  ad 
quartum  ventriculum.  The  third  ventricle  is  crossed  by  three 
commissures,  anterior,  middle,  and  posterior ;  and  between  these 
are  two  spaces,  called  foramen  commune  anterius  and  foramen 
commune  posterius. 

The  anterior  commissure  is  a  small  rounded  white  cord,  which 
enters  the  corpus  striatum  at  either  side,  and  spreads  out  in  the 
substance  of  the  hemispheres  ;  the  middle  or  soft  commissure 
consists  of  gray  matter,  which  is  continuous  with  the  gray  lining 
of  the  ventricle ;  it  connects  the  adjacent  sides  of  the  thalami  optici ; 
the  posterior  commissure,  smaller  than  the  anterior,  is  a  flattened 
white  cord,  connecting  the  two  thalami  optici  posteriorly. 

The  space  between  the  anterior  and  middle  commissure  is  called 
the  foramen  commune  anterius,  and  is  that  to  which  Monro  has 
given  his  name  (foramen  of  Monro).  It  is  the  medium  of  com- 
munication between  the  two  lateral  and  third  ventricle,  and 
transmits  superiorly  the  choroid  plexus  and  venae  corporum  stria- 
tornin.  The  foramen  commune  anterius  is  also  termed  iter  ad 
infnndibulum,  from  leading  downwards  to  the  funnel-shaped  cavity 
of  the  infundibulum.  The  crura  of  the  fornix  are  embedded  in 
the  lateral  walls  of  the  foramen  commune,  and  are  concealed  from 
view  in  this  situation  by  the  layer  of  gray  substance  which  lines 
the  interior  of  the  third  ventricle.  If  the  crura  be  slightly  sepa- 
rated, the  anterior  commissure  will  be  seen  immediately  in  front 
of  them,  crossing  from  one  corpus  striatura  to  the  other.  Thtf 


222  THE   DISSECTOR. 

space  between  the  middle  and  posterior  commissure  is  the  fora- 
men commune  posterius  ;  it  is  much  shallower  than  the  preceding, 
and  is  the  origin  of  a  canal,  the  aqueduct  of  Sylvius,  or  iter  a  tertio 
ad  quartum  ventriculum,  which  leads  backwards  beneath  the  pos- 
terior commissure  and  through  the  base  of  the  corpora  quadri- 
gemina  to  the  upper  part  of  the  fourth  ventricle. 

CORPORA  QUADRIGEMINA. — The  corpora  quadrigemina,  or  optic 
lobes,  are  situated  immediately  behind  the  third  ventricle  and 
posterior  commissure ;  and  beneath  the  posterior  border  of  the 
corpus  callosum.  They  form,  indeed,  at  this  point,  the  inferior 
boundary  of  the  transverse  fissure  of  the  hemispheres,  the  fissure 
of  Bichat.  The  anterior  pair  of  these  bodies  are  gray  in  color, 
and  are  named  nates:  the  posterior  pair  are  white  and  much 
smaller  than  the  anterior:  they  are  termed  testes.  From  the 
nates  on  each  side  may  be  traced  a  rounded  process  (brachium 
anterius)  which  passes  obliquely  outwards  into  the  thalamus 
opticus  ;  and  from  the  testis  a  similar  but  smaller  process  (bra- 
chium posterius)  which  has  the  same  destination.  The  corpus 
geniculatum  internum  lies  in  the  interval  of  these  two  processes, 
where  they  enter  the  thalamus  ;  and  behind  the  brachium  posterius 
is  a  prominent  band  (laqueus)  which  marks  the  course  of  the 
superior  division  of  the  fasciculus  olivaris.  The  corpora  quadri- 
gemina are  perforated  longitudinally  through  their  base  by  the 
aqueduct  of  Sylvius ;  they  are  covered  in  partly  by  the  pia  mater 
and  partly  by  the  velum  interpositum,  and  the  nates  support  the 
pineal  gland. 

PINEAL  GLAND. — The  pineal  gland  is  a  small  reddish-gray 
body  of  a  conical  form  (hence  its  synonym  conarium},  situated 
on  the  anterior  part  of  the  nates  and  invested  by  a  duplicature 
of  pia  mater  derived  from  the  under  part  of  the  velum  interposi- 
tum. The  pineal  gland,  when  pressed  between  the  fingers,  is 
found  to  contain  a  gritty  matter  (acervulus)  composed  chemically 
of  phosphate  and  carbonate  of  lime,  and  phosphate  of  magnesia 
and  ammonia,  and  is  sometimes  hollow  in  the  interior.  It  is 
connected  to  the  brain  by  means  of  two  medullary  cords  called 
peduncles,  and  a  thin  lamina  derived  from  the  posterior  commis- 
sure ;  the  peduncles  of  the  pineal  gland  are  attached  to  the  thalami 
optici,  and  may  be  traced  along  the  upper  and  inner  margin  of 
those  bodies  to  the  crura  of  the  fornix,  with  which  they  become 
blended.  From  the  close  connection  subsisting  between  the  pia 
mater  and  the  pineal  gland,  and  the  softness  of  texture  of  the 
latter,  the  gland  is  liable  to  be  torn  away  in  the  removal  of  the 
pia  mater. 

Behind  the  corpora  quadrigemina  is  the  cerebellum,  and  beneath  the 
cerebellum,  the  fourth  ventricle.  The  student  must  therefore  divide  the 
cerebellum  down  to  the  fourth  ventricle,  and  turn  its  lobes  aside  tQ 
examine  that  cavity. 


FOURTH   VENTRICLE.  223 

FOURTH  VENTRICLE. — The  fourth  ventricle  (sinns  rhomboi- 
dalis)  is  the  ventricle  of  the  cerebellum.  It  is  situated  on  the 
posterior  surface  of  the  medulla  oblongata  and  pons  Varolii,  is 
lozenge-shaped  in  its  form,  and  bounded  on  each  side  by  a  thick 
cord  passing  between  the  cerebellum  and  corpora  quadrigemina, 
called  the  processus  e  cerebello  ad  testes,  and  by  the  corpus  resti- 
forme.  It  is  covered  in  behind  by  the  cerebellum,  and  by  a  thin 
lamella  of  medullary  substance,  stretched  between  the  two  pro- 
cessus e  cerebello  ad  testes,  termed  the  valve  of  Vieussens.1 

That  portion  of  the  cerebellum  which  forms  the  posterior 
boundary  of  the  fourth  ventricle,  presents  four  small  prominences 
or  lobules,  and  a  thin  layer  of  medullary  substance,  the  velum 
medullare  posterius.  Of  the  lobules  two  are  placed  in  the  middle 
line,  the  nodulus  and  uvula,  the  former  being  before  the  latter; 
the  remaining  two  are  named  amygdalce,  or  tonsils,  and  are 
situated  one  on  either  side  of  the  uvula.  They  all  project  into 
the  cavity  of  the  fourth  ventricle,  and  the  velum  medullare  pos- 
terius is  situated  in  front  of  them.  The  valve  of  Vieussens  or 
velum  raedullare  anterius  is  an  extremely  thin  lamella  of  medul- 
lary substance,  prolonged  from  the  white  matter  of  the  cerebel- 
lum to  the  testes,  and  attached  on  each  side  to  the  processus  e 
cerebello  ad  testes.  This  lamella  is  overlaid  for  a  short  distance 
by  a  thin,  transversely  grooved  lobule  of  gray  substance  (lin- 
guetta  laminosa)  derived  from  the  anterior  border  of  the  cerebel- 
lum, and  its  junction  with  the  testes  is  strengthened  by  a  narrow 
slip  given  off  by  the  commissure  of  those  bodies,  the  frcenulum 
reli  medullaris  anterioris.  The  anterior  wall,  or  floor  of  the 
fourth  ventricle,  is  formed  by  two  slightly  convex  bodies,  fasci- 
culi teretes  (innominati),  separated  by  a  longitudinal  groove 
which  is  continuous  inferiorly  with  the  posterior  median  fissure 
of  the  spinal  cord.  On  these  bodies  the  gray  substance  (fasciolae 
cinereffi)  derived  from  the  interior  of  the  medulla  is  spread  out, 
and  at  the  lower  part  of  the  ventricle  forms  several  eminences  or 
nuclei,  from  which,  according  to  Stilling,  the  eighth  and  ninth 
nerves,  and  probably  also  the  fifth,  take  their  origin.  Higher  up 
the  fasciculi  teretes  are  crossed  by  several  white  strise  (linese 
transverse),  the  origin  of  the  auditory  nerves.  Upon  the  lower 
part  of  the  floor  of  this  ventricle  is  an  impression  resembling  the 
point  of  a  pen,  and  hence  named  calamus  scriptorius ;  the  lateral 
boundaries  of  the  calamus  are  the  processus  clavati  of  the  poste- 
rior pyramids.  Above,  the  fourth  ventricle  is  bounded  by  the 
corpora  quadrigemina  and  aqueduct  of  Sylvius;  and  below  by  a 

1  Raymond  Vieussens,  a  great  discoverer  in  the  anatomy  of  the  brain 
and  nervous  system.  His  "  Neurographia  Universalis"  was  published  in 
Jjyons  in  1685, 


224  THE   DISSECTOR. 

layer  of  pia  mater  and  arachnoid,  called  the  valve  of  the  arach- 
noid. Beneath  this  valve  a  communication  exists  between  the 
ventricles  of  the  brain  and  the.  sub-arachnoid ean  space.  Within 
the  fourth  ventricle,  and  lying  against  the  uvula  and  tonsils,  are 
two  small  vascular  fringes  formed  by  the  pia  mater,  the  choroid 
plexuses  of  the  fourth  ventricle. 

LINING   MEMBRANE   OP   THE   VENTRICLES. 

The  lining  membrane  of  the  ventricles  is  a  serous  layer  distinct 
from  the  arachnoid ;  it  lines  the  whole  of  the  interior  of  the 
lateral  ventricles,  and  is  connected  above  and  below  with  the 
attached  border  of  the  choroid  plexus,  so  as  to  exclude  all  com- 
munication between  the  lateral  ventricles  and  the  exterior  of  the 
brain.  From  the  lateral  ventricles  it  is  reflected  through  the 
foramen  of  Monro,  on  each  side,  into  the  third  ventricle,  which 
it  invests  throughout.  From  the  third  it  is  conducted  into  the 
fourth  ventricle,  through  the  iter  i\  tertio  ad  quartum  ventricu- 
lum,  and,  after  lining  its  interior,  becomes  continuous  inferiorly 
with  the  subarachnoidean  space  of  the  spinal  cord.  The  lining 
membrane  of  the  ventricles  is  provided  with  a  ciliated  epithelium, 
and  is  the  source  of  the  secretion  which  moistens  and  lubricates 
their  interior.  The  fifth  ventricle  has  a  separate  lining  mem- 
brane. 

CEREBELLUM. 

The  cerebellum,  seven  times  smaller  than  the  cerebrum,  is 
situated  beneath  the  posterior  lobes  of  the  latter,  being  lodged 
in  the  posterior  fossa  of  the  base  of  the  cranium,  and  protected 
from  the  superincumbent  pressure  of  the  cerebrum  by  the  tento- 
rium  cerebelli.  Like  the  cerebrum,  it  is  composed  of  gray  and 
white  substance,  the  former  occupying  the  surface,  the  latter  the 
interior ;  and  its  surface  is  formed  of  parallel  lamellae  separated 
by  sulci,  and  here  and  there  by  deeper  sulci.  In  form,  the  cere- 
bellum is  oblong  and  flattened,  its  greater  diameter  being  from 
side  to  side,  its  two  surfaces  looking  upwards  and  downwards, 
and  its  borders  being  anterior,  posterior,  and  lateral.  In  con- 
sideration of  its  shape,  the  cerebellum  admits  of  a  division  into 
two  hemispheres,  into  certain  prominences  termed  processes  and 
lobules,  and  into  certain  divisions  of  its  substance  called  lobes, 
formed  upon  the  hemispheres  by  the  deeper  sulci  above  referred 
to.  The  two  hemispheres  are  separated  from  each  other  on  the 
upper  surface  of  the  cerebellum  by  a  longitudinal  ridge,  which  is 
termed  the  superior  vermijorm  process,  and  which  forms  a  com- 
missure between  them.  On  the  anterior  border  of  the  organ 
there  is  a  semilunar  notch,  incisura  cerebelli  anterior,  which  en- 
circles the  corpora  quadrigemina  posteriorly.  On  the  posterior 


CEREBELLUM.  225 

border  there  is  another  notch,  incisura  cere  belli  posterior,  which 
receives  the  upper  part  of  the  falx  cerebelli :  and  on  the  under 
surface  of  the  cerebellum  is  a  deep  fissure  corresponding  with  the 
medulla  oblongata,  and  termed  the  vallecula  (valley). 

Each  hemisphere  of  the  cerebellum  is  divided  by  means  of  a 
fissure  (sulcus  horizontals)  which  runs  along  its  free  border,  into 
an  upper  and  a  lower  portion  ;  and  upon  each  of  these  portions 
certain  lobes  are  marked  out.  Thus  on  the  upper  portion  there 
are  two  such  lobes  separated  by  a  sulcus,  somewhat  more  strongly 
marked  than  the  rest,  and  extending  deeper  into  the  substance 
of  the  cerebellum.  They  are  the  lobus  superior  anterior  and  lobus 
superior  posterior.  Upon  the  under  portion  of  the  hemisphere 
there  are  three  such  lobes,  namely,  lobus  inferior  anterior,  medius, 
and  posterior,  and  two  additional  ones  of  peculiar  form,  the  lobus 
inferior  internus,  or  tonsil,  and  the  flocculus.  The  tonsil  (amyg- 
dala) is  situated  on  the  side  of  the  vallecula,  and  projects  into 
the  fourth  ventricle.  The  flocculus,  or  pneumogastric  lobule, 
long  and  slender,  extends  from  the  side  of  the  vallecula,  around 
the  corpus  restiforme  to  the  crus  cerebelli,  lying  behind  the  fila- 
ments of  the  eighth  pair  of  nerves. 

The  commissure  between  the  two  hemispheres  is  termed  the 
worm  (vermis),  that  portion  of  the  worm  which  occupies  the 
upper  surface  of  the  cerebellum  as  far  back  as  the  horizontal 
fissure  being  the  processus  vermiformis  superior,  and  that  which 
is  lodged  within  the  vallecula  being  the  processus  vermiformis 
inferior.  The  superior  vermiform  process  is  a  prominent  longi- 
tudinal ridge,  extending  from  the  iucisura  anterior  to  the  incisura 
posterior  cerebelli.  In  imitation  of  the  hemispheres,  it  is  divided 
into  lobes,  of  which  three  have  received  names,  namely,  the  lobu- 
lus  centralis,  which  is  a  small  lobe  situated  in  the  incisura  ante- 
rior ;  the  monticulus  cerebelli,  a  longer  lobe,  having  its  peak  and 
declivity;  and  a  small  lobe  near  the  incisura  posterior,  the  com- 
missura  simplex.  The  lobes  of  the  inferior  vermiform  process 
are  four  in  number,  namely,  the  commissura  brevis,  situated  in 
the  incisura  posterior,  below  the  horizontal  fissure ;  the  pyramid, 
a  small,  obtusely-pointed  eminence  ;  a  larger  prominence,  the 
uvula,  situated  between  the  tonsils,  and  connected  with  them  by 
means  of  a  commissure  ;  and  in  front  of  the  uvula  the  nodulus. 
In  front  of  the  nodulus  is  a  thin  lamina  of  medullary  substance, 
consisting  of  a  central  and  two  lateral  portions,  the  velum  medul- 
lare  posterius  (valvula  Tarini) ;  and  between  this  velum  and  the 
nodulus  and  uvula  is  a  deep  fossa,  which  is  known  as  the  swal- 
low's nest  (nidus  hirundinis).  The  velum  medullare  anterius  is 
the  valve  of  Vieussens,  described  with  the  fourth  ventricle.  Both 
these  vela  proceed  from  the  same  point  in  the  roof  of  that  ven- 


226  THE   DISSECTOR. 

tricle,  and  separate  from  each  other  at  an  angle,  the  one  passing 
obliquely  forwards,  the  other  obliquely  backwards. 

When  a  vertical  incision  is  made  into  the  cerebellum,  that 
appearance  is  seen  which  has  been  denominated  arbor  vita 
cerebelli.  The  white  substance  in  the  centre  of  such  a  section 
resembles  the  trunk  of  a  tree,  from  which  the  branches  are  given 
off,  and  from  the  branches,  branchlets  and  leaves,  the  two  latter 
being  coated  by  a  moderately  thick  and  uniform  layer  of  gray 
substance.  If  the  incision  be  made  somewhat  nearer  the  commis- 
sure than  to  the  lateral  border  of  the  organ,  a  yellowish-gray 
dentated  line,  inclosing  medullary  substance  traversed  by  the 
openings  of  numerous  vessels,  will  be  seen  in  the  centre  of  the 
white  substance.  This  is  the  ganglion  of  the  cerebellum,  the 
corpus  rhomboideum  or  dentatum,  from  which  the  peduncles  of 
the  cerebellum  proceed.  The  gray  line  is  dense  and  horny  in 
structure,  and  is  the  cut  edge  of  a  thin  capsule,  open  towards  the 
medulla  oblongata. 

The  cerebellum  is  associated  with  the  rest  of  the  encephalon 
by  means  of  three  pairs  of  rounded  cords  or  peduncles — supe- 
rior, middle,  and  inferior.  The  superior  peduncles,  or  processus 
e  cerebetto  ad  testes,  proceed  from  the  cerebellum  forwards  and 
upwards  to  the  testes,  in  which  they  are  lost.  They  form  the 
anterior  part  of  the  lateral  boundaries  of  the  fourth  ventricle, 
and  give  attachment  by  their  inner  borders  to  the  valve  of 
Yieussens,  which  is  stretched  between  them.  At  their  junction 
with  the  testes  they  are  crossed  by  the  fourth  pair  of  nerves. 
The  middle  peduncles,  or  crura  cerebelli  ad  pontem,  the  largest 
of  the  three,  issue  from  the  cerebellum  through  the  anterior  ex- 
tremity of  the  sulcus  horizontalis,  and  are  lost  in  the  pons 
Yarolii.  The  inferior  peduncles,  or  crura  ad  medullam  oUonga- 
tam,  are  the  corpora  restiformia  which  descend  to  the  posterior 
part  of  the  medulla  oblongata  and  form  the  inferior  portion  of 
the  lateral  boundaries  of  the  fourth  ventricle. 

BASE  OF  THE  BRAIN. 

The  student  should  now  prepare  to  study  the  base  of  the  brain :  for 
this  purpose  the  organ  should  be  turned  upon  its  incised  surface  ;  and  if 
the  dissection  have  hitherto  been  conducted  with  care,  he  will  find  the 
base  uninjured.  The  arachnoid  membrane,  some  parts  of  the  pia  mater, 
and  the  circle  of  Willis,  must  be  carefully  cleared  away,  in  order  to  ex- 
pose all  the  parts  to  be  examined.  These  he  will  find  arranged  in  the 
following  order  from  before  backwards  : — 

Longitudinal  fissure,  Commencement  of  the  trans- 
Olfactory  nerves,  verse  fissure, 
Fissure  of  Sylvius,  Optic  commissure, 
Substantia  perforata  ;  Tuber  cinereum, 


BASE   OF   THE   BRAIN. 


227 


Infundibulum;  Pons  Yarolii, 

Corpora  albicantia,  Crura  cerebelli, 

Locus  perforatus,  Medulla  oblongata. 

Crura  cerebri ; 

The  longitudinal  fissure  is  the  space  separating  the  two  he- 
mispheres :  it  is  continued  downwards  to  the  base  of  the  brain, 
and  divides  the  two  anterior  lobes.  In  this  fissure  the  anterior 

THE  UNDER  SURFACE  OB  Fig.  67. 

BASE  OF  THE  BRAIN. — 1. 
The  anterior  lobe  of  one  he- 
misphere of  the  cerebrum. 
2.  The  middle  lobe.  3.  The 
posterior  lobe  almost  con- 
cealed by  (4)  the  lateral  lobe 
of  the  cerebellum.  5.  The 
inferior  vermiform  process 
of  the  cerebellum.  6.  The 
pneumogastric  lobule.  7. 
The  longitudinal  fissure.  8. 
The  olfactory  nerves,  with 
their  bulbous  expansions. 
9.  The  substantia  perforata 
at  the  inner  termination  of 
the  fissure  of  Sylvius;  the 
three  roots  of  the  olfactory 
nerve  are  seen  upon  the  sub- 
gtantia  perforata.  The  com- 
mencement of  the  transverse 
fi .--.-•  ure  on  each  side  is  con- 
cealed by  the  inner  border 
of  the  middle  lobe.  10.  The 
commissure  of  the  optio 
nerves.  11.  The  tuber  cine- 
reum,  from  which  the  infun- 
dibulum  is  seen  projecting. 

12.  The  corpora  albicantia. 

13.  The    locus    perforatus, 

bounded  on  each  side  by  the  crura  cerebri,  and  by  the  third  nerve.  14.  The 
pons  Varolii.  15.  The  crus  cerebelli  of  one  side.  16.  The  fifth  nerve  emerg- 
ing from  the  anterior  border  of  the  crus  cerebelli ;  the  small  nerve  by  its  side 
is  the  fourth.  17.  The  sixth  pair  of  nerves.  18.  The  seventh  pair  of  nerves, 
consisting  of  the  auditory  and  facial.  19.  The  corpora  pyramidalia  of  the  me- 
dulla oblongata  ;  the  corpus  olivare  and  part  of  the  corpus  restiforme  are  seen 
at  each  side.  Just  below  the  number  is  the  decussation  of  the  fibres  of  the 
corpora  pyramidalia.  20.  The  eighth  pair  of  nerves.  21.  The  ninth  or  hypo- 
glossal  nerve.  22.  The  anterior  root  of  the  first  cervical  spinal  ner^e. 

cerebral  arteries  ascend  towards  the  corpus  callosum  :  and,  if 
the  two  lobes  be  slightly  drawn  asunder,  the  anterior  border 
(genu)  of  the  corpus  callosum  will  be  seen  descending  to  the 
base  of  the  brain.  Arrived  at  the  base  of  the  brain,  the  corpus 
callosum  terminates  by  a  concave  border,  which  is  prolonged  to 
the  commissure  of  the  optic  nerves  by  a  thin  layer  of  gray  sub- 
stance, the  lamina  cinerea.  The  lamina  cinerea  is  the  anterior 


228  THE   DISSECTOR. 

part  of  the  inferior  boundary  of  the  third  ventricle.  On  each 
side  of  the  lamina  cinerea  the  corpus  callosum  is  continued  into 
the  substantia  perforata  and  crura  cerebri,  and  upon  the  latter 
forms  a  narrow  medullary  band  lying  externally  to,  and  slightly 
overlapping,  the  optic  tract,  the  medulla  innominata. 

Upon  the  under  surface  of  each  anterior  lobe,  on  either  side 
of  the  longitudinal  fissure,  is  the  olfactory  nerve,  with  its  bulb. 

The  fissure  of  Sylvius  bounds  the  anterior  lobe  posteriorly, 
and  separates  it  from  the  middle  lobe ;  it  lodges  the  middle  cere- 
bral artery.  If  this  fissure  be  followed  outwards,  a  small  isolated 
cluster  of  five  or  six  convolutions  (gyri  operti),  will  be  observed; 
these  constitute  the  island  of  Reil.  The  island  of  Reil,  together 
with  the  substantia  perforata,  form  the  base  of  the  corpus 
striatum. 

The  substantia  perforata  (locus  perforatus  anticus),  is  a  trian- 
gular plane  of  white  substance,  situated  at  the  inner  extremity 
of  the  fissure  of  Sylvius.  It  is  named  perforata,  from  being 
pierced  by  a  number  of  openings  for  small  arteries,  which  enter 
the  brain  in  this  situation  to  supply  the  gray  substance  of  the 
corpus  striatum. 

Passing  backwards  on  each  side  beneath  the  edge  of  the 
middle  lobe,  is  the  commencement  of  the  great  transverse  fissure, 
which  extends  beneath  the  hemisphere  of  one  side  to. the  same 
point  on  the  opposite  side.  A  probe  passed  into  this  fissure  be- 
tween the  crus  cerebri  and  middle  lobe  would  enter  the  middle 
cornu  of  the  lateral  ventricle. 

The  optic  commissure  is  situated  on  the  middle  line ;  it  is  the 
point  of  communication  between  the  two  optic  nerves. 

The  tuber  cinereum  is  an  eminence  of  gray  substance  situated 
immediately  behind  the  optic  commissure,  and  in  front  of  the 
corpora  mammillaria.  From  its  centre  there  projects  a  small 
conical  body  of  gray  substance,  apparently  a  prolongation  of  the 
tuber  cinereum,  the  infundibulum.  The  infundibulum  is  hollow 
in  its  interior,  inclosing  a  short  caecal  canal,  which  communicates 
with  the  cavity  of  the  third  ventricle ;  and  below  the  termination 
of  the  canal,  the  conical  process  becomes  connected  with  the 
pituitary  gland.  The  infundibulum  and  tuber  cinereum  form 
part  of  the  floor  of  the  third  ventricle. 

The  pituitary  gland  (hypophysis  cerebri)  is  a  small,  flattened, 
reddish-gray  body  situated  in  the  sella  turcica,  and  closely  re- 
tained in  that  situation  by  the  dura  mater  and  arachnoid.  It 
consists  of  two  lobes,  closely  pressed  together,  the  anterior  lobe 
being  the  larger  of  the  two  and  oblong  in  shape,  the  posterior 
round.  Both  lobes  are  connected  with  the  infundibulum,  but 
the  latter  is  so  soft  in  texture  as  to  be  generally  torn  through  in 
the  removal  of  the  brain.  Indeed,  for  the  purposes  of  the  stu- 


BASE   OP   THE   BRAIN. 


dent,  it  is  better  to  effect  this  separation  with  the  knife,  and 
leave  the  pituitary  body  in  situ,  to  be  examined  with  the  base  of 
the  cranium. 

The  corpora  albicantia  (mammillaria,  pisiformia,  bulbi  for- 
nicis)  are  two  white  convex  bodies,  having  the  shape  and  size  of 
peas,  rdtuated  behind  the  tuber  cinereum,  and  between  the  crura 
cerebri.  They  are  a  part  of  the  crura  of  the  fornix,  which,  after 
their  origin  from  the  thalami  optici,  descend  to  the  base  of  the 


\ 


ANATOMY  OP  THE  BASE  OF  Fig.  68. 

THE  BRAIN. — a,  a.  The  ante- 
rior lobes  of  the  cerebrum. 
b,  b.  The  middle  lobes,  c,  c. 
The  cerebellum,  d.  The  lon- 
gitudinal fissure  of  the  cere- 
brum. 1,  1.  The  first  pair, 
or  olfactory  nerves,  e,  e.  The 
bulbi  olfactorii.  /,  /.  The 
three  roots  of  origin  of  the 
olf;n-t<>ry  nerve  ;  externally  to 
the  letter  is  the  fissure  of 
Sylvius,  g,  g.  The  substan- 
tia  perforata.  2.  The  second 
pair,  or  optic  nerves;  the 
figure  rests  on  the  optic  com- 
missure, h.  The  tuber  cine- 
reum, on  the  summit  of  which 
is  seen  the  infundibulum  cut 
across.  «',  *'.  The  corpora  al- 
bicantia. k.  The  locus  per- 
foratus.  3,  3.  The  third  pair 
of  nerves:  the  figures  are 
placed  on  the  crura  cerebri. 
/.  The  pons  Varolii.  m,  m. 
The  crura  cerebelli.  4,  4. 
The  fourth  pair  of  nerves. 
5,  5.  The  fifth  pair,  issuing 
from  the  crura  cerebelli.  6. 
The  sixth  pair.  7,  7.  The 
seventh  pair;  the  smaller 
nerve  is  the  portio  dura 
11,  n.  The  corpora  pyramidalia  of  the  medulla  oblongata.  o.  The  medulla  spi- 
nalis ;  just  above  the  letter  is  seen  the  decussation  of  the  fibres  of  the  corpora 
liyrninidalia.  p.  One  of  the  corpora  olivaria;  the  other  is  concealed  by  the 
filaments  of  the  ninth  nerve,  q.  One  of  the  corpora  restiformia;  the  other  is 
concealed  by  the  filaments  of  the  eighth  nerve.  8.  The  eighth  nerve  ;  consist- 
ing of  r,  the  glosso-pharyngeal ;  5,  the  pneumogastric ;  t ,  the  spinal  accessory. 
9.  The  ninth,  or  hypoglossal  nerve,  v,  v.  The  anterior  roots  of  the  two  upper 
spinal  nerves,  w,  w.  The  pneumogastric  lobules  of  the  cerebellum,  x,  x.  The 
border  of  the  lobus  superior  of  the  cerebellum,  y,  y.  The  border  of  the  lobus 
inferior  anterior.  The  fissure  between  x  and  y  is  the  sulcus  horizontal. 

brain,  and  making  a  sudden  curve  upon  themselves  previously  to 
their  ascent  to  the  lateral  ventricles,  constitute  the  corpora  albi- 
cantia. When  divided  by  section,  these  bodies  will  be  found  to 
be  composed  of  a  capsule  of  white  substance,  containing  gray 
20 


230  THE  DISSECTOR. 

matter,  the  gray  matter  of  the  two  corpora  being  connected  by 
means  of  a  commissure. 

The  locus  perforatus  (posticus)  is  a  layer  of  whitish-gray  sub- 
stance, connected  in  front  with  the  corpora  albicantia,  behind 
with  the  pons  Yarolii,  and  on  each  side  with  the  crura  cerebri, 
between  which  it  is  situated.  It  is  perforated  by  several  thick 
tufts  of  arteries,  which  are  distributed  to  the  thalami  optici  and 
third  ventricles,  of  which  latter  it.  assists  in  forming  the  floor.  It 
is  also  called  the  pons  Tarini. 

The  crura  cerebri  (peduncles  of  the  cerebrum)  are  two  thick 
white  cords,  which  issue  from  the  anterior  border  of  the  pons 
Yarolii,  and  diverge  to  each  side  to  enter  the  thalami  optici.  By 
their  outer  side  the  crura  cerebri  are  continuous  with  the  corpora 
quadrigemina,  and  above,  they  constitute  the  lower  boundary  of 
the  aqueduct  of  Sylvius.  In  their  interior,  they  contain  gray 
matter,  which  has  a  semilunar  shape  when  the  crus  is  divided 
transversely,  and  has  been  termed  the  locus  niger.  The  third 
nerve  will  be  observed  to  arise  from  the  inner  side  of  each  crus, 
and  the  fourth  nerves  wind  around  their  outer  border  from  above. 

The  pons  Varolii1  (protuberantia  annularis,  nodus  encephali)  is 
the  broad  transverse  band  of  white  fibres  which  arches  like  a 
bridge  across  the  upper  part  of  the  medulla  oblongata  ;  and,  con- 
tracting on  each  side  into  a  thick  rounded  cord,  enters  the  sub- 
stance of  the  cerebellum  under  the  name  of  crus  cerebelli.  There 
is  a  groove  along  its  middle  which  lodges  the  basilar  artery.  The 
pons  Yarolii  is  the  commissure  of  the  cerebellum,  and  associates 
the  two  lateral  lobes  in  their  common  functions.  Resting  against 
the  pons,  near  its  posterior  border,  is  the  sixth  pair  of  nerves. 
On  the  anterior  border  of  the  crus  cerebelli,  at  each  side,  is  the 
thick  bundle  of  filaments  belonging  to  the  fifth  nerve,  and,  lying 
against  its  posterior  border,  the  seventh  pair  of  nerves.  The 
upper  surface  of  the  pons  forms  a  part  of  the  floor  of  the  fourth 
ventricle. 

MEDULLA  OBLONGATA. 

The  medulla  oblongata  (bulbus  rachidicus)  is  the  upper  en- 
larged portion  of  the  spinal  cord.  It  is  somewhat  conical  in 
shape,  and  a  little  more  than  an  inch  in  length,  extending  from 
the  pons  Yarolii  to  a  point  corresponding  with  the  upper  border 
of  the  atlas.  On  the  middle  line,  in  front  and  behind,  the  medulla 

1  Constant  Varolius,  Professor  of  Anatomy  in  Bologna  :  lie  died  in  1578. 
He  dissected  the  brain  in  the  course  of  its  fibres,  beginning  from  the 
medulla  oblongata  ;  a  plan  which  has  since  been  perfected  by  Vieussens, 
and  by  Gall  and  Spurzheim.  The  work,  containing  his  mode  of  dissec- 
tion, "De  Resolutione  Corporis  Humani,"  was  published  after  his  death, 
in  1591. 


MEDULLA  OBLONGATA. 


231 


oblongata  is  marked  by  two  vertical  fissures,  the  anterior  and 
posterior  median  fissures,  which  divide  it  superficially  into  two 


Fig.  69. 


AN  ANTERIOR  VIEW  OP  THE 
MEDULLA  OBLONOATA. — a,  a. 
Anterior  pyramids.  b.  Their 
decussation  across  the  middle 
line,  c,  c.  The  olivary  bodies. 
d,  d.  Restiform  bodies,  e.  Arci- 
form  fibres,  f.  Fibres  shown  by 
Solly  to  pass  from  the  anterior 
column  of  the  cord  to  the  cere- 
bellum, g.  Anterior  column. 
h.  Lateral  column,  p.  Pona 
Varolii.  i.  Its  upper  fibres. 
5,  5.  Roots  of  fifth  nerves. 


Fig.  70. 


r\ 


POSTERIOR  VIEW  OP  THE  MEDULLA. 
OBLONOATA,  AND  BACK  OF  THE  PONS 
VAROLII. — The  peduncles  of  the  cere- 
bellum are  cut  short,  d,  d.  Restiform 
bodies  (fasciculi  cuneati),  passing  up  to 
become  inferior  peduncles  of  cerebellum. 
p,  p.  Posterior  pyramids,  v,  v.  Posterior 
fissure,  or  calamus  scriptorius,  extending 
along  the  floor  of  the  fourth  ventricle. 
a,  a.  Testes.  b,  b.  Nates.  /,/.  Superior 
peduncles  of  cerebellum,  c.  Eminence 
connected  with  hypoglossal  nerve,  e. 
With  glosso-pharyngeal  nerve,  i.  With 
vagus  nerve,  v.  With  spinal  accessory 
nerve.  7,  7.  Roots  of  auditory  nerves. 


symmetrical  lateral  cords  or  columns ;  whilst  each  lateral  column 
is  subdivided  by  minor  grooves  into  three  smaller  cords,  namely, 
the  corpora  pyramidalia,  corpora  olivaria,  and  corpora  restiformia. 
The  corpora  pyramidalia  are  two  narrow  convex  cords,  tapering 
slightly  from  above  downwards,  and  situated  one  on  either  side 
of  the  anterior  median  fissure.  At  about  an  inch  below  the  pons 
the  corpora  pyramidalia  communicate  very  freely  across  the  fissure 
by  a  decussation  of  their  fibres,  and  at  their  point  of  entrance 
into  the  pons  they  are  constricted  into  round  cords.  The  fissure 
is  somewhat  enlarged  by  this  constriction,  and  the  enlarged  space 


232  THE   DISSECTOR. 

has  received  the  name  of  foramen  caecum  (Yicq  d'Azyr)  of  the 
medulla  oblongata. 

The  corpora  olivaria  (named  from  some  resemblance  to  the 
shape  of  an  olive)  are  two  oblong,  oval-shaped,  convex  bodies, 
of  about  the  same  breadth  with  the  corpora  pyramidalia,  about 
half  an  inch  in  length,  and  somewhat  larger  above  than  below. 
The  corpus  olivare  is  situated  immediately  external  to  the  corpus 
pyramidale,  from  which,  and  from  the  corpus  restiforme,  it  is 
separated  by  a  well-marked  groove.  In  this  groove  some  longi- 
tudinal fibres  are  seen  which  inclose  the  base  of  the  corpus  olivare, 
and  have  been  named  funiculi  siliquce,  those  which  lie  to  its  inner 
side  being  the  funiculus  internus,  and  those  to  its  outer  side  the 
funiculus  externus.  Besides  these  there  are  other  fibres  which 
cross  the  corpus  olivare  obliquely  :  these  are  ihejibrtE  arciformes. 
When  examined  by  section,  the  corpus  olivare  is  found  to  be  a 
ganglion  deeply  embedded  in  the  medulla  oblongata,  and  meeting 
its  fellow  at  the  middle  line  behind  the  corpus  pyramidale.  The 
ganglion  of  the  corpus  olivare  (corpus  dentatum,  nucleus  olivae), 
like  that  of  the  cerebellum,  is  a  yellowish-gray  dentated  capsule, 
open  behind,  and  containing  medullary  substance  from  which  a 
fasciculus  of  fibres  proceeds  upwards  to  the  corpora  quadrigemina 
and  thalami  optici.  The  nervous  filaments  which  spring  from 
the  groove  on  the  anterior  border  of  the  corpus  olivare,  are  those 
of  the  hypoglossal  nerve ;  and  those  on  its  posterior  border  are 
the  glosso-pharyngeal  and  pneuraogastric. 

The  corpora  restiformia  (restis,  a  rope)  comprehend  the  whole 
of  the  posterior  half  of  each  lateral  column  of  the  medulla  oblon- 
gata. They  are  separated  from  the  corpora  olivaria  by  the 
grooves  already  spoken  of ;  posteriorly,  they  are  divided  from 
each  other  by  the  posterior  median  fissure  and  the  fourth  ventri- 
cle, and  superiorly  they  diverge  and  curve  backwards  to  enter 
the  cerebellum,  and  constitute  its  inferior  peduncles.  Along  the 
posterior  border  of  each  corpus  restiforme,  and  marked  off  from 
that  body  by  a  groove,  is  a  narrow  white  cord,  separated  from  its 
fellow  by  the  posterior  fissure.  This  pair  of  narrow  cords  are 
termed  the  posterior  pyramids  (fasciculi  graciles).  Each  fasci- 
culus forms  an  enlargement  (processus  clavatus)  at  its  upper  end, 
and  is  then  lost  in  the  corresponding  corpus  restiforme.  The 
processus  clavati  are  the  lateral  boundaries  of  the  nib  of  the 
calamus  scriptorius.  The  corpus  restiforme  is  crossed  near  its 
entrance  into  the  cerebellum  by  the  auditory  nerve,  the  choroid 
plexus  of  the  fourth  ventricle,  and  the  pneumogastric  lobule. 

The  remaining  portion  of  the  medulla  oblongata  visible  from 
the  exterior,  are  the  two  slightly  convex  columns  which  enter  into 
the  formation  of  the  floor  of  the  fourth  ventricle.  These  columns 
are  the  fasciculi  teretes  (innominati). 


FIBRES  OP  THE  BRAIN.  233 

DIVERGING  FIBRES. — The  fibres  composing  the  columns  of  the  medulla 
oblongata  have  a  special  arrangement  on  reaching  the  upper  part  of  that 
body;  those  of  the  corpora  pyramidalia  and  olivaria  enter  the  pons 
Varolii,  and  are  thence  prolonged  through  the  crura  cerebri,  thalami 
optici,  and  corpora  striata  to  the  cerebral  hemispheres  ;  but  those  of  the 
corpora  restiformia  are  reflected  backwards  into  the  cerebellum,  and  form 
its  inferior  peduncles. 

From  pursuing  this  course,  and  spreading  out  as  they  advance,  these 
fibres  have  been  termed  by  Gall  the  diverging  fibres.  While  situated 
within  the  pons,  the  fibres  of  the  corpus  pyramidale  and  olivare  separate 
and  spread  out,  and  have  gray  substance  interposed  between  them ;  and 
they  quit  the  pons,  much  increased  in  number  and  bulk,  so  as  to  form 
the  crus  cerebri.  The  fibres  of  the  crus  cerebri  again  are  separated  in  the 
thalamus  opticus,  and  are  intermingled  with  gray  matter,  and  they  also 
quit  that  body  greatly  increased  in  number  and  bulk.  Precisely  the 
same  change  takes  place  in  the  corpus  striatum,  and  the  fibres  are  now  so 
extraordinarily  multiplied  as  to  be  capable  of  forming  a  large  proportion 
of  the  hemispheres. 

Observing  this  remarkable  increase  in  the  white  fibres,  apparently  from 
the  admixture  of  gray  substance,  Gall  and  Spurzheim  considered  the 
latter  as  the  material  increase  of  formative  substance  to  the  white  fibres, 
and  they  are  borne  out  in  this  conclusion  by  several  collateral  facts, 
among  the  most  prominent  of  which  is  the  great  vascularity  of  the  gray 
substance ;  the  larger  proportion  of  the  nutrient  fluid  circulating  through 
it  is  fully  capable  of  effecting  the  increased  growth  and  nutrition  of  the 
structures  by  which  it  is  surrounded.  For  a  like  reason,  the  bodies  in 
which  this  gray  substance  occurs,  are  called  by  the  same  physiologists 
"  ganglia  of  increase"  and  by  other  authors  simply  ganglia.  Thus,  the 
thalami  optici  and  corpora  striata  are  the  ganglia  of  the  cerebrum ;  or,  in 
other  words,  informative  ganglia  of  the  hemispheres. 

The  fibres  of  the  corpora  pyramidalia  are  not  all  of  them  destined  to 
the  course  above  described  ;  several  fasciculi  curve  outwards  to  reach  the 
corpora  restiformia,  some  passing  in  front  and  some  behind  the  corpus 
olivare  on  each  side.  These  are  the  ar cif or m  fibres;  they  are  distinguish- 
ed by  Mr.  Solly  into  the  superficial  and  deep  cerebellar  fibres.  In  the  pons 
Varolii  the  continued  or  cerebral  fibres  (Solly)  of  the  corpus  pyramidale 
are  placed  between  the  superficial  and  deep  layers  of  transverse  fibres, 
and,  escaping  from  the  pons,  constitute  the  inferior  and  inner  segment  of 
the  crus  cerebri.  From  the  crus  cerebri  they  pass  for  the  most  part  be- 
neath the  thalami  optici  into  the  corpora  striata. 

The  fibres  which  inclose  the  corpus  olivare,  under  the  name  of  fasci- 
culi siliquae,  are  separated  by  that  body  into  two  bands  ;  the  innermost 
of  the  two  bands,  fun ic ulus  siliquce  internus,  accompanies  the  fibres  of  the 
corpus  pyramidale  into  the  crus  cerebri.  The  funiculus  siliquce  externus 
unites  with  a  fasciculus  proceeding  from  the  nucleus  olivae,  and  the  com- 
bined column  ascending  behind  the  crus  cerebelli  divides  into  a  superior 
and  an  inferior  band.  The  inferior  band  proceeds  with  a  fasciculus 
presently  to  be  described,  the  fasciculus  innominatus,  into  the  upper  seg- 
ment of  the  crus  cerebri.  The  superior  band  (laqueus)  ascends  by  the 
side  of  the  processus  e  cerebello  ad  testes,  and,  crossing  the  latter  ob- 
liquely, enters  the  corpora  quadrigemina,  in  which  many  of  its  fibres  are 
distributed,  while  the  rest  are  continued  onwards  into  the  thalamus 
opticus. 

The  corpora  restiformia  derive  their  fibres  from  the  anterior  as  well  as 
from  the  posterior  columns  of  the  medulla  oblongata ;  they  diverge  as 

20* 


234  THE   DISSECTOR. 

they  approach  the  cerebellum,  and  leaving  between  them  the  cavity  of 
the  fourth  ventricle,  enter  the  substance  of  the  cerebellum,  under  the 
form  of  two  rounded  cords.  These  cords  envelop  the  corpora  rhomboidea, 
or  ganglia  of  increase,  and  then  expand  on  all  sides  so  as  to  constitute 
the  cerebellum. 

Besides  the  fibres  here  described,  there  are,  in  the  interior  of  the  me- 
dulla oblongata,  behind  the  corpora  olivaria,  and  more  or  less  apparent 
between  these  bodies  and  the  corpora  restiformia,  two  large  bundles  of 
fibres,  fhe  fasciculi  innominati.  These  fasciculi  ascend  behind  the  deep 
transverse  fibres  of  the  pons  Varolii,  and  become  apparent  in  the  floor  of 
the  fourth  ventricle,  under  the  name  of  fasciculi  teretes.  From  this  point 
they  are  prolonged  upwards  beneath  the  corpora  quadrigemina  into  the 
crura  cerebri,  of  which  they  form  the  upper  and  outer  segment,  and  are 
thence  continued  through  the  thalami  optici  and  corpora  striata  into  the 
hemispheres.  The  locus  niger  of  the  cms  cerebri  is  a  septum  of  gray 
matter  interposed  between  these  fasciculi  and  those  of  the  corpora 
pyramidalia. 

CONVERGING  FIBRES. — In  addition  to  the  diverging  fibres  which  are  thus 
shown  to  constitute  both  the  cerebrum  and  cerebellum,  by  their  increase 
and  development,  another  set  of  fibres  are  found  to  exist,  which  have  for 
their  office  the  association  of  the  symmetrical  halves  and  distant  parts  of 
the  same  hemispheres. 

These  are  called  from  their  direction  converging  fibres,  and  from  their 
office  commissures.  The  commissures  of  the  cerebrum  and  cerebellum  are, 
the— 

Corpus  callosum,  Middle  commissure, 

Fornix,  Posterior  commissure, 

Septum  lucidum,  Peduncles  of  pineal  gland, 

Anterior  commissure,  Pons  Varolii. 

The  corpus  callosum  is  the  commissure  of  the  hemispheres.  It  is  there- 
fore of  moderate  thickness  in  the  middle,  where  its  fibres  pass  directly 
from  one  hemisphere  to  the  other;  thicker  in  front  (genu),  where  the 
anterior  lobes  are  connected  ;  and  thickest  behind  (splenium),  where  the 
fibres  from  the  posterior  lobes  are  assembled.  The  fibres  which  curve 
backwards  into  the  posterior  lobes  from  the  splenium  of  the  corpus  callo- 
sum have  been  termed  forceps,  those  which  pass  directly  outwards  into 
the  middle  lobes  from  the  same  point,  tapetum,  and  those  which  curve 
forwards  and  inwards  from  the  genu  to  the  anterior  lobes,  forceps  anterior. 

The  fornix  is  an  antero-posterior  commissure,  and  serves  to  connect  a 
number  of  parts.  Below,  it  is  associated  with  the  tenia  semicircularis, 
thalami  optici,  and  peduncles  of  the  pineal  gland  ;  on  each  side,  by  means 
of  the  corpora  fimbriata,  with  the  middle  lobes  of  the  brain  ;  and,  above, 
with  the  corpus  callosum,  and  consequently  with  the  hemispheres. 

The  septum  lucidum  is  a  perpendicular  commissure  between  the  fornix 
and  corpus  callosum. 

The  anterior  commissure  traverses  the  corpus  striatum,  and  connects  the 
anterior  and  middle  lobes  of  opposite  hemispheres.  The  middle  commis- 
sure is  a  layer  of  gray  substance,  uniting  the  thalami  optici.  The  posterior 
commissure  is  a  white  rounded  cord,  connecting  the  thalami  optici. 

The  peduncles  of  the  pineal  gland  must  also  be  regarded  as  commis- 
sures, assisted  in  their  function  by  the  gray  substance  of  the  gland. 

The  pons  Varolii  is  the  commissure  to  the  two  hemispheres  of  the  cere- 
bellum. It  consists  of  transverse  fibres,  which  are  split  into  two  layers 
by  the  passage  of  the  fasciculi  of  the  corpora  pyramidalia  and  corpora 
olivaria.  These  two  layers,  the  superior  and  inferior,  are  collected  to- 
gether on  each  side,  in  the  formation  of  the  crura  cerebelli. 


CRANIAL   NERVES. 


235 


CRANIAL  NERVES. 


Having  studied  the  parts  consti- 
tuting the  base  of  the  brain,  the  dis- 
sector may  now  proceed  to  examine 
the  origins  of  the  cranial  nerves,  and, 
where  necessary,  trace  them  through 
the  substance  of  the  brain  to  their  real 
source. 

There  are  nine  pairs*  of  cranial 
nerves,  which,  taken  in  their  order 
from  before  backwards,  are  as  fol- 
lows : — 

1st.  Olfactory. 
2d.  Optic. 

3d.  Motores  ocnlorum. 
4th.  Pathetici  (trochleares). 
5th.  Trifacial  (trigemini). 
6th.  Abducentes. 
*  ,       (Facial  (portio  dura). 
'    |  Auditory  (portio  mollis). 

f  Glosso-pharyngeal. 
Q.I     J  Pneumogastric  (vagus,  par 
th"   1          vagum). 

[  Spinal  accessory. 
9th.  Hypoglossal  (lingual). 

Functionally  or  physiologically 
the  cranial  nerves  admit  of  divi- 
sion into  three  groups,  namely, 
nerves  of  special  sense,  nerves  of 
motion,  and  compound  nerves, 
that  is,  nerves  which  contain  fibres 
both  of  sensation  and  motion. 
The  nerves  belonging  to  these 
groups  are  the  following  : — 


FRONT  VIEW  OF  CRURA  CEREBRI, 
PONS,  MEDULLA  OBLONGATA,  AND 

PART  OF  THE  SPINAL  CORD.   The 

origins  of  some  of  the  cranial  nerves 
are  shown.  2.  Optic  nerve.  3. 
Motor  oculi.  4.  Pathetic  nerve. 
5.  Fifth,  or  trifacial  nerve.  6.  Ab- 
ducent nerve.  7.  Auditory  and  fa- 
cial nerves — seventh  pair.  8.  Eighth 
pair,  including  glosso-pharyngeal, 
vagus,  and  spinal  accessory  nerves. 
9.  Hypoglossal  nerve.  1.  A  spinal 
nerve. 


'  [The  author  in  the  classification  of  these  nerves  has  adopted  that  of 
Willis,  which  is  in  general  use  ;  but  that  of  Soemmering  is  undoubtedly 
pivtWabl.',  because  it  is  the  moat  natural;  it  gives  us  twelve  pairs  of 
cranial  nerves.  Of  these  two  are  considered  as  entering  the  internal 
auditory  in.-atus,  and  three  pass  out  of  the  posterior  foramen  lacerum. 
Soemmering's  classification  is  as  follows  :  — 

Th«-  first  6  the  same  as  above. 

1>  Facia1' 
Auditory. 
Glosso-pharyngeal. 
Pneumogastric. 
Spinal  accessory. 


7th  nf 
7th  of 


9th 


7th 
gth 

9th 
10th 
llth 
12th 


Hypoglossal.] 


236  THE   DISSECTOR. 

1st.  Olfactory. 


Special  sense, 


Motion 


Compound 


2d.  Optic. 

7th.  Auditory. 

3d.  Motores  oculorum. 

4th.  Pathetici. 

6th.  Abdncentes. 

Tth.  Facial. 

9th.  Hypoglossal. 

5th.  Trifacial. 

8th.  Glosso-pharyngeal. 


Pneumogastric. 
Spinal  accessory. 

FIRST  PAIR  :  OLFACTORY. — The  olfactory  nerve  arises  by  three 
roots ;  an  inner  root  from  the  inner  and  posterior  part  of  the 
anterior  lobe,  close  to  the  substantia  perforata  ;  a  middle  root 
from  a  papilla  of  gray  matter  (caruncula  mammillaris),  embedded 
in  the  anterior  lobe ;  and  an  external  root,  which  may  be  traced 
as  a  white  streak  along  the  fissure  of  Sylvius  into  the  corpus 
striatum,  where  it  is  continuous  with  some  of  the  fibres  of  the 
anterior  commissure.  The  nervous  cord  formed  by  the  union  of 
these  three  roots  is  soft  in  texture,  prisinoid  in  shape,  and  embed- 
ded in  a  sulcus  between  two  convolutions  on  the  under  surface  of 
each  anterior  lobe  of  the  brain,  lying  between  the  pia  mater  and 
the  arachnoid.  As  it  passes  forwards  it  increases  in  breadth,  and 
swells  at  its  extremity  into  an  oblong  mass  of  gray  and  white 
substance,  the  bulbus  olfactorius,  which  rests  upon  the  cribriform 
lamella  of  the  ethmoid  bone.  From  the  under  surface  of  the 
bulbus  olfactorius  are  given  off  the  nerves  which  pass  through 
the  cribriform  foramina  and  supply  the  mucous  membrane  of  the 
nares. 

SECOND  PAIR  :  OPTIC. — The  optic  nerve,  a  nerve  of  large  size, 
arises  from  the  corpora  geniculata  on  the  posterior  and  inferior 
aspect  of  the  thalamus  opticus,  from  the  thalamus  itself,  and  from 
the  nates.  Proceeding  from  this  origin,  it  winds  around  the  crus 
cerebri  as  a  flattened  band,  under  the  name  of  tractus  opticus, 
and  joins  with  its  fellow  in  front  of  the  tuber  cinereum  to  form 
the  optic  commissure  (chiasma).  The  tractus  opticus  is  united 
with  the  crus  cerebri  and  tuber  cinereum,  and  is  covered  in  by 
the  pia  mater ;  the  commissure  is  also  connected  with  the  tuber 
cinereum,  from  which  it  receives  fibres,  and  the  nerve  beyond  the 
commissure  diverges  from  its  fellow,  becomes  rounded  in  form, 
and  is  inclosed  in  a  sheath  derived  from  the  arachnoid.  The 
commissure  rests  on  the  processns  olivaris  of  the  sphenoid  bone, 
and  is  composed  of  the  fibres  of  the  two  nerves ;  the  innermost 
fibres  cross  each  other  to  pass  to  opposite  eyes,  while  the  outer 


ORIGIN   OF   OPTIC   NERVES. 


23t 


fibres  continue  their  course  uninterruptedly  to  the  eye  of  the  cor- 
responding side.  The  neurilemma  of  the  commissure,  as  well  as 
that  of  the  nerves,  is  formed  by  the  pia  mater. 

THIRD  PAIR  :  MOTORES  OCULORUM. — The  motor  oculi,  a  nerve 
of  moderate  size,  arises  from  the  inner  side  of  the  cms  cerebri, 
close  to  the  pons  Yarolii,  and  passes  forward  between  the  poste- 
rior cerebral  and  superior  cerebellar  artery. 

The  fibres  of  origin  of  this  nerve  may  be  traced  into  the  gray 
substance  of  the  crus  cerebri,1  into  the  motor  tract,8  and  as  far  as 

Pig.  72. 


THE  ORIGIN  AND  DISTRIBUTION  OF  THE  OPTIC  NERVES. — 1,  1.  The  thalami 
optici,  their  upper  surface.  2.  The  middle  commissure  of  the  third  ventricle, 
connecting  the  two  thalami.  3.  The  posterior  commissure  of  the  third  ven- 
tricle. 4.  The  foramen  commune  posterius.  5.  The  corpus  geniculatum  inter- 
num.  6.  The  corpus  genicnlatum  externum.  7.  The  corpora  quadrigemina  : 
the  anterior  pair  are  the  nates,  the  posterior  the  testes.  8.  One  root  of  the 
optic  nerve,  arising  from  the  corpus  geniculatum  externum  9.  The  other  root, 
arising  from  the  nates.  10.  The  commissure.  11.  The  expansion  of  the  optic 
nerve  into  the  retina.  12.  A  section  of  the  retina,  showing  its  three  layers  :  the 
external  is  Jacob's  membrane,  the  next  the  nervous,  and  the  internal  the  vas- 
cular, formed  by  the  ramifications  of  the  arteria  centralis  retinae,  which  is  seen 
at  13,  piercing  the  optic  nerve,  and  running  forwards  in  the  centre  of  that  nerve. 


Mayo. 


Solly. 


THE  DISSECTOR. 

the  corpora  quadrigemina  and  valve  of  Yieussens.  In  the  caver- 
nous sinus  it  receives  one  or  two  filaments  from  the  carotid 
plexus,  and  one  from  the  ophthalmic  nerve. 

FOURTH  PAIR  :  PATHETICT  (trochlearis). — The  fourth  is  the 
smallest  cerebral  nerve;  it  arises  from  the  valve  of  Yieussens 
close  to  the  testis,  and  winds  around  the  crus  cerebri  to  the  base 
of  the  brain. 

FIFTH  PAIR  :  TRIFACIAL  (trigeminus.) — The  fifth  nerve,  the 
great  sensitive  nerve  of  the  head  and  face,  and  the  largest  cranial 
nerve,  is  analogous  to  the  spinal  nerves  in  its  origin  by  two 
roots  from  the  anterior  and  posterior  columns  of  the  spinal  cord, 
and  in  the  existence  of  a  ganglion  on  the  posterior  root.  It 
arises1  from  a  tract  of  yellowish-white  matter  situated  in  front  of 
the  floor  of  the  fourth  ventricle  and  the  origin  of  the  auditory 
nerve,  and  behind  the  crus  cerebelli.  This  tract  divides  infe- 
riorly  into  two  fasciculi  which  may  be  traced  downwards  into  the 
spinal  cord,  one  being  continuous  with  the  fibres  of  the  anterior 
column,  the  other  with  the  posterior  column.  Proceeding  from 
this  origin,  the  two  roots  of  the  nerve  pass  forward,  and  issue 
from  the  brain  upon  the  anterior  part  of  the  crus  cerebelli,  where 
they  are  separated  by  a  slight  interval.  The  anterior  is  much 
smaller  than  the  posterior,  and  the  two  together  constitute  the 
fifth  nerve,  which,  in  this  situation,  consists  of  seventy  to  a  hun- 
dred filaments  held  together  by  pia  mater. 

SIXTH  PAIR  :  ABDUCENTES. — The  abducens  nerve,  about  half 
the  size  of  the  motor  oculi,  arises  by  several  filaments  from  the 
upper  constricted  part  of  the  corpus  pyramidale,  close  to  the 
pons  Yarolii.  Proceeding  forwards  from  this  origin,  it  lies 
parallel  with  the  basilar  artery.  Mr.  Mayo  traced  the  origin  of 
this  nerve  between  the  fasciculi  of  the  corpora  pyramidalia  to  the 
posterior  part  of  the  medulla  oblongata;  and  Mr.  Grainger 
pointed  out  its  connection  with  the  gray  substance  of  the  spinal 
cord. 

SEVENTH  PAIR. — The  seventh  pair  consists  of  two  nerves 
which  lie  side  by  side  on  the  posterior  border  of  the  crus  cere- 
belli. The  smaller  and  most  internal  of  these,  and,  at  the  same 
time,  the  most  dense  in  texture,  is  the  facial  nerve,  or  portio 
dura.  The  external  nerve,  which  is  soft  and  pulpy,  and  often 
grooved  by  contact  with  the  preceding,  is  the  auditory  nerve,  or 
portio  mollis  of  the  seventh  pair. 

FACIAL  NERVE  (portio  dura). — The  facial  nerve,  the  motor 
nerve  of  the  face,  arises  from  the  upper  part  of  the  groove  be- 

1  I  have  adopted  the  origin  of  this  nerve  given  by  Dr.  Alcock,  of 
Dublin,  in  the  Cyclopaedia  of  Anatomy  and  Physiology,  as  the  result  of 
his  dissections.  Mr.  Mayo  also  traces  the  anterior  root  of  the  nerve  to  a 
similar  origin. 


ORIGIN  OP  EIGHTH  PAIR.  239 

tween  the  corpus  olivare  and  the  corpus  restiforme,  close  to  the 
pons  Varolii,  from  which  point  its  fibres  may  be  traced  deeply 
into  the  corpus  restiforme.  The  nerve  then  passes  forwards, 
resting  on  the  crus  cerebelli,  and  comes  into  relation  with  the 
auditory  nerve,  with  which  it  enters  the  meatus  auditorius  in- 
ternus. 

AUDITORY  NERVE  (portio  mollis). — The  auditory  nerve  takes 
its  origin  in  the  lineae  transversie  (striae  medullares)  of  the  ante- 
Fig.  73. 


THK  ORIGIN  AND  DISTRIBUTION  OF  THE  AUDITORY  NERVE. — I.  The  corpora 
quadrigemina.  2,  2.  The  processus  e  cerebello  ad  testes,  at  each  side.  3,  3. 
The  corpora  restiformia.  4.  The  space  included  between  these  four  bodies,  the 
fourth  ventricle.  5.  The  opening  of  the  canal  of  communication  which  leads 
from  the  third  ventricle,  the  iter  &  tertio  ad  quartum  ventriculum.  6.  The 
calamus  scriptorius.  7.  The  posterior  median  columns  of  the  spinal  cord, 
which  form  by  their  divergence  the  point  of  the  calamus,  which  is  also  called 
the  ventricle  of  Arantius.  8.  The  lineae  transversae  of  the  fourth  ventricle, 
which  are  the  lines  of  origin  of  the  auditory  nerve.  9.  The  anterior  branch  of 
the  auditory  nerve,  distributed  to  the  cochlea.  10.  The  posterior,  or  vestibu- 
lar  branch.  11.  The  utriculus  communis,  which  conceals  the  sacculus  proprius 
from  view.  12.  The  ampulla  of  the  oblique  semicircular  canal.  13.  The  am- 
pullae of  the  perpendicular  and  horizontal  semicircular  canals. 

rior  wall  or  floor  of  the  fourth  ventricle,  and  winds  around  the 
corpus  restiforme,  from  which  it  receives  fibres,  to  the  posterior 
border  of  the  crus  cerebelli,  where  it  comes  into  relation  with 
the  facial  nerve.  From  the  softness  of  texture  of  the  nerve,  it 
presents  a  groove  on  its  superior  surface  for  the  reception  of  the 
portio  dura.  The  auditory  nerve  is  the  eighth  pair  of  Soem- 
mering. 

EIGHTH  PAIR. — The  eighth  pair  consists  of  three  nerves,  the 
glosso-pharyngeal,  pneumogastric,  and  spinal  accessory  :  these 
are  the  ninth,  tenth,  and  eleventh  pairs  of  Soemmering. 


240  THE   DISSECTOR. 

GLOSSO-PHARYNGEAL  NERVE. — This  nerve  arises  by  five  or  six 
filaments  from  the  groove  between  the  corpus  olivare  and  resti- 
forme,  or  rather  from  the  anterior  border  of  the  latter.  The 
filaments  unite  to  form  a  nerve  of  moderate  size.  The  fibres  of 
origin  may  be  traced  through  the  fasciculi  of  the  corpus  resti- 
forme  to  the  gray  substance  in  the  floor  of  the  fourth  ventricle. 

PNEUMOGASTRIC  NERVE  (vagus). — The  pneumogastric  arises 
by  ten  or  fifteen  filaments  from  the  groove  between  the  corpus 
olivare  and  corpus  restiforme,  or  rather  from  the  anterior  border 
of  the  latter,  immediately  below  the  glosso-pharyngeal.  The 
fibres  of  origin  may  be  traced,  like  those  of  the  glosso-pharyn- 
geal, to  the  gray  substance  in  the  floor  of  the  fourth  ventricle. 

SPINAL  ACCESSORY. — The  spinal  accessory  nerve  arises  by 
several  filaments  from  the  side  of  the  spinal  cord,  as  low  down  as 
the  fifth  or  sixth  cervical  nerve,  and  ascends  behind  the  ligamen- 
tum  denticulatuin  and  between  the  anterior  and  posterior  roots 
of  the  spinal  nerves  to  the  side  of  the  medulla  oblongata,  where 
it  comes  into  relation  with  the  two  preceding  nerves. 

NINTH  PAIR  :  HYPOGLOSSAL  NERVE  (lingual). — The  hypoglos- 
sal  nerve  arises  from  the  groove  between  the  corpus  pyramidale 
and  corpus  olivare  by  ten  or  fifteen  filaments,  which  are  collected 
into  two  bundles.  The  bundles  unite  and  form  a  nerve  of  con- 
siderable size. 

At  its  origin,  the  hypoglossal  nerve  sometimes  communicates 
with  the  posterior  root  of  the  first  cervical  nerve.  Its  deep  ori- 
gin may  be  traced  to  the  gray  substance  in  the  floor  of  the  fourth 
ventricle. 

The  student  may  now  return  to  the  cranium  to  examine  the  nerves  in 
their  passage  through  the  dura  mater  and  the  foramina  in  the  base  of  the 
skull. 

The  olfactory  bulb  sends  its  numerous  small  nerves  through  the 
cribriform  foramina  of  the  ethmoid  bone,  in  the  sulcus  situated 
on  either  side  of  the  attachment  of  the  falx  cerebri  to  the  crista 
galli. 

The  optic  nerve  passes  through  the  optic  foramen,  and  receives 
in  its  passage  a  sheath  from  the  dura  mater.  The  dura  mater  at 
this  point  divides  into  two  layers,  one  being  continuous  with  the 
periosteum  of  the  orbit,  the  other  being  the  sheath  of  the  optic 
nerve.  The  ophthalmic  artery  enters  the  orbit  through  the  optic 
foramen,  with  the  optic  nerve  lying  to  its  outer  side. 

The  third,  or  motor  oculi  nerve,  passes  through  an  opening  in 
the  dura  mater  situated  immediately  in  front  of  the  posterior 
clinoid  process,  and  takes  its  course  through  the  outer  wall  of 
the  cavernous  sinus  to  the  sphenoidal  fissure  through  which  it 
enters  the  orbit. 

The  fourth  nerve  passes  through  the  dura  mater  a  little  further 


COURSE   OF   CRANIAL   NERVES.  241 

back,  and  externally  to  the  third  nerve.  It  also  takes  its  course 
through  the  outer  wall  of  the  cavernous  sinus  to  the  sphenoidal 
fissure,  by  which  it  enters  the  orbit  (pp.  133,  134). 

The  ffth  nerve  passes  through  a  large  oval  opening  in  the  dura 
mater,  immediately  behind  and  to  the  outer  side  of  the  fourth 
nerve.  This  opening  is  situated  in  the  anterior  part  of  the  ten- 
torium  cerebelli  at  its  insertion  into  the  petrous  bone,  and  the 
nerve  lies  in  a  groove  on  the  border  of  that  bone  near  its  extre- 
mity. After  passing  through  this  opening,  the  nerve  enters  the 
Casserian  ganglion ;  and  if  the  ganglion  be  gently  raised,  the 
anterior  root  of  the  fifth  nerve  will  be  seen  passing  beneath  the 
ganglionic  mass  to  join  with  the  inferior  maxillary  nerve. 

The  sixth  nerve  enters  an  opening  in  the  dura  mater  behind 
and  to  the  inner  side  of  the  opening  for  the  fifth  nerve,  and 
ascends  upon  the  body  of  the  sphenoid  bone  to  reach  the  cavern- 
ous sinus  below  the  other  nerves.  It  lies  in  the  inner  wall  of 
the  sinus,  between  the  sinus  and  the  internal  carotid  artery,  and 
passes  into  the  orbit  through  the  sphenoidal  fissure. 

The  seventh  pair  of  nerves,  consisting  of  the  facial  and  audi- 
tory, enter  the  meatus  auditorius  internus,  which  is  lined  by  the 
dura  mater.  The  facial  nerve  lies  in  front  of  the  auditory ;  and 
a  small  artery,  the  internal  auditory,  a  branch  of  the  superior 
cerebellar,  enters  with  them  to  be  distributed  to  the  internal  ear. 
At  the  bottom  of  the  meatus  auditorius  internus  the  facial  nerve 
enters  its  special  canal,  the  aqueductus  Fallopii,  and  the  auditory 
nerve  divides  into  a  number  of  small  branches  which  pass  into 
the  cochlea  and  vestibule. 

The  eighth  pair  of  nerves,  the  glosso-pharyngeal,  pneumo- 
gastric,  and  spinal  accessory,  pass  through  the  dura  mater  and 
jugular  foramen,  behind  and  to  the  inner  side  of  the  seventh  pair. 
The  glosso-pharyngeal  pierces  the  dura  mater  separately,  and  in 
front  of  the  other  two,  and  receives  a  sheath  from  that  membrane 
in  its  passage.  The  pneumogastric  and  the  spinal  accessory 
also  receive  a  sheath,  which  is  common  to  the  two  nerves. 

The  ninth,  or  hypoglossal  nerve,  pierces  the  dura  mater  by  two 
or  three  separate  filaments  to  the  inner  side  of  the  eighth  pair, 
and  near  the  foramen  magnum.  Having  passed  through  the 
dura  mater,  the  filaments  unite  into  a  single  nerve  at  the  anterior 
condyloid  foramen  ;  and  the  nerve  receives  a  sheath  from  the 
dura  mater. 

Immediately  behind,  and  to  the  inner  side  of  the  optic  foramen, 
the  internal  carotid  artery  will  be  seen  emerging  from  the  dura 
mater.  And  just  below  the  margin  of  the  foramen  magnum,  on 
either  side,  is  the  trunk  of  the  vertebral  artery  penetrating  the 
dura  mater. 

The  pituitary  gland  will  be  seen  occupying  the  sella  turcica, 
21 


242 


THE   DISSECTOR. 


and  surrounded  by  that  portion  of  the  dura  mater  which  stretches 
between  the  clinoid  processes. 

To  dissect  the  gland,  the  dura  mater  surrounding  it  must  be  turned 
aside  and  the  posterior  clinoid  processes  broken  off;  but  as  this  pre- 
paration would  injure  the  parts  contained  in  the  cavernous  sinuses,  it 
may  be  omitted  until  the  cavernous  sinuses  have  been  examined  and 
are  completed. 

The  gland  is  composed  of  two  lobes,  and  the  remains  of  the 
infundibulum  will  be  seen  attached  to  its  upper  surface  (page 
228). 


Fig.  74. 


THE  SINUSES  OF  THE 
UPPER  AND  BACK  PART 
OP  THE  SKULL. — 1.  The 
superior  longitudinal  si- 
nus. 2,  2.  The  cerebral 
veins  opening  into  the 
sinus  from  behind  for- 
wards. 3.  Thefalx  cere- 
bri.  4.  The  inferior  longi- 
tudinal sinus.  5.  The 
straight  or  fourth  sinus. 
6.  The  venae  Galeni.  7. 
The  torcular  Herophili. 
8.  The  two  lateral  sinuses, 
with  the  occipital  sinuses 
between  them.  9.  The 
termination  of  the  inferior 
petrosal  sinus  of  one  side. 
10.  The  dilatations  corre- 
sponding with  the  jugular 
fossae.  11.  The  internal 
jugular  veins. 


SINUSES  OF  THE  CRANIUM. 

The  sinuses  of  the  dura  mater  are  irregular  channels,  formed 
by  the  splitting  of  the  layers  of  that  membrane,  and  lined  upon 
their  inner  surface  by  a  continuation  of  the  internal  coat  of  the 
veins.  They  may  be  divided  into  two  groups  :  1.  Those  situ- 
ated at  the  upper  and  back  part  of  the  skull.  2.  The  sinuses  at 
the  base  of  the  skull.  The  former  are,  the — 

Superior  longitudinal  sinus,  Occipital  sinuses, 

Inferior  longitudinal  sinus,  Lateral  sinuses. 

Straight  sinus, 

The  only  dissection  required  for  the  sinuses,  with  the  exception  of  the 
cavernous  sinus,  is  to  lay  them  open  with  the  scissors  or  scalpel.  The 
cavernous  requires  to  be  isolated  after  the  examination  of  the  nerves 
which  occupy  its  external  wall. 

The  superior  longitudinal  sinus  is  situated  in  the  attached 
margin  of  the  falx  cerebri,  and  extends  along  the  middle  line  of 


SINUSES   OF   THE   CRANIUM.  243 

the  arch  of  the  skull,  from  the  foramen  caecum  in  the  frontal,  to 
the  inner  tuberosity  of  the  occipital  bone,  where  it  divides  into 
the  two  lateral  sinuses.  It  is  triangular  in  form,  is  small  in 
front,  and  increases  gradually  in  size  as  it  passes  backwards  ;  it 
receives  the  superior  cerebral  veins  which  open  into  it  obliquely, 
numerous  small  veins  from  the  diploe,  and  near  the  posterior 
extremity  of  the  sagittal  suture,  the  parietal  veins,  from  the  pe- 
ricranium and  scalp.  Examined  in  its  interior,  it  presents  nu- 
merous transverse  fibrous  bands  (trabecula?),  the  chords  Wiliisii, 
which  are  stretched  across  its  inferior  angle ;  and  some  small 
white  granular  masses,  the  glandulae  Pacchioni ;  the  oblique  open- 
ings of  the  cerebral  veins,  with  their  valve-like  margin,  are  also 
seen  on  the  walls  of  the  sinus. 

The  termination  of  the  superior  longitudinal  sinus  in  the  two 
lateral  sinuses  forms  a  considerable  dilatation,  into  which  the 
straight  sinus  opens  from  the  front,  and  the  occipital  sinuses 
from  below.  This  dilatation  is  named  the  torcular  Herophili,1 
and  is  the  point  of  communication  of  six  sinuses,  the  superior 
longitudinal,  two  lateral,  two  occipital,  and  the  straight. 

The  inferior  longitudinal  sinus  is  situated  in  the  free  margin 
of  the  falx  cerebri;  it  is  cylindrical  in  form,  and  extends  from 
near  the  crista  galli  to  the  anterior  border  of  the  tentorium, 
where  it  terminates  in  the  straight  sinus.  "  It  receives  in  its  course 
several  veins  from  the  falx. 

The  straight,  or  fourth  sinus,  is  the  sinus  of  the  tentorium:  it 
is  situated  at  the  line  of  union  of  the  falx  with  the  tentorium  ;  is 
prismoid  in  form,  and  extends  across  the  tentorium,  from  the 
termination  of  the  inferior  longitudinal  sinus  to  the  torcular  Hero- 
phili.  It  receives  the  vena3  Galeni,a  the  cerebral  veins  from  the 
inferior  part  of  the  posterior  lobes,  and  the  superior  cerebellar 
veins. 

The  occipital  sinuses  are  two  canals  of  small  size,  situated  in 
the  -attached  border  of  the  falx  cerebelli ;  they  commence  by 
several  small  veins  around  the  foramen  magnum,  and  terminate 
by  separate  openings  in  the  torcular  Herophili.  They  not  unfre- 
quently  communicate  with  the  termination  of  the  lateral  sinuses. 

The  lateral  sinuses,  commencing  at  the  torcular  Herophili, 
pass  horizontally  outwards,  in  the  attached  margin  of  the  tento- 
rium,  and  then  curve  downwards  and  inwards  along  the  base  of 

1  Torcular  (a  press),  from  a  supposition  entertained  by  the  older  ana  • 
toniists  that  the  columns  of  blood,  coming  in  different  directions,  com- 
pressed each  other  at  this  point. 

Herophilus  was  a  great  anatomist,  and  was  well  informed  on  many 
parts  of  the  human  structure;  he  lived  about  500  years  before  Christ.. 

2  Claudian  Galen,  chief  of  the  Greek  physicians  after  Hippocrates,  was 
born  about  the  year  130. 


244 


THE   DISSECTOR. 


Pig.  75. 


the  petrous  portion  of  the  temporal  bone,  at  each  side,  to  the 
foramina  lacera  posteriora,  where  they  terminate  in  the  internal 
jugular  veins.  Each  sinus  rests  in  its  course  on  the  transverse 
groove  of  the  occipital  bone,  posterior  inferior  angle  of  the  parie- 
tal, mastoid  portion  of  the  temporal,  and  again  on  the  occipital 
bone.  They  receive  the  cerebral  veins  from  the  inferior  surface 
of  the  posterior  lobes,  the  inferior  cerebellar  veins,  the  superior 
petrosal  sinuses,  the  mastoid  and  posterior  condyloid  veins,  and, 
at  their  termination,  the  inferior  petrosal  sinuses.  These  sinuses 
are  often  unequal  in  size,  the  right  being  larger  than  the  left. 
The  sinuses  of  the  base  of  the  skull  are,  the — 

Cavernous,  Superior  petrosal, 

Inferior  petrosal,  Transverse. 

Circular, 

The  cavernous  sinuses  are  named  from  presenting  a  structure 
similar  to  that  of  the  corpus  cavernosum  penis.  They  are  situ- 
ated on  each  side  of  the  sella  turcica,  receiving,  anteriorly,  the 
ophthalmic  veins  through  the  sphenoidal  fissures,  and  terminating 
posteriorly  in  the  inferior  petrosal  sinuses.  In  the  internal  wall 

of  each  cavernous  sinus  is  the  in- 
ternal carotid  artery,  accompa- 
nied by  several  filaments  of  the 
carotid  plexus,  and  crossed  by  the 
sixth  nerve  ;  and,  in  its  external 
wall,  the  third,  fourth,  and  oph- 
thalmic nerves.  These  structures 
are  separated  from  the  blood  flow- 
ing through  the  sinus,  by  the 
tubular  lining  membrane.  The 
cerebral  veins  from  the  under  sur- 
face of  the  anterior  lobes  open 
into  the  cavernous  sinuses.  They 
communicate  by  means  of  the  oph- 
thalmic with  the  facial  veins,  by 
the  circular  sinus  with  each  other, 
and  by  the  superior  petrosal  with 
the  lateral  sinuses. 

The  inferior  petrosal  sinuses  are 
the  continuations  of  the  cavernous 
sinuses  backwards  along  the  lower 
border  of  the  petrous  portion  of 

THE  SINUSES  OF  THE  BASE  OF  THE  SKULL. — 1.  The  ophthalmic  veins.  2. 
The  cavernous  sinus  of  one  side.  '  3.  The  circular  sinus;  the  figure  occupies 
the  position  of  the  pituitary  gland  in  the  sella  turcica.  4.  The  inferior  petrosal 
sinus.  5.  The  transverse  or  anterior  occipital  sinus.  6.  The  superior  petrosal 
sinus.  7.  The  internal  jugular  vein.  8.  The  foramen  magnum.  9.  The  occi- 
pital sinuses.  10.  The  torcular  Herophili.  11,  11.  The  lateral  sinuses. 


SINUSES   OP   THE   CRANIUM.  245 

the  temporal  bone  at  each  side  of  the  base  of  the  skull;  to  the 
foramina  lacera  posteriora,  where  they  terminate  with  the  lateral 
sinuses  in  the  commencement  of  the  internal  jugular  veins. 

The  circular  sinus  (sinus  of  Ridley)  is  situated  in  the  sell  a 
turcica,  surrounding  the  pituitary  gland,  and  communicating  on 
each  side  with  the  cavernous  sinus.  The  posterior  segment  is 
larger  than  the  anterior. 

The  superior  petrosal  sinuses  pass  obliquely  backwards  along 
the  attached  border  of  tentorium  on  the  upper  margin  of  the 
petrous  portion  of  the  temporal  bone,  and  establish  a  communi- 
cation between  the  cavernous  and  lateral  sinus  at  each  side. 
They  receive  one  or  two  cerebral  veins  from  the  inferior  part  of 
the  middle  lobes,  and  a  cerebellar  vein  from  the  anterior  border 
of  the  cerebellum.  Near  the  extremity  of  the  petrous  bone  these 
sinuses  cross  the  oval  aperture  which  transmits  the  fifth  nerve. 

The  transverse  sinus  (basilar,  anterior  occipital)  passes  trans- 
versely across  the  basilar  process  of  the  occipital  bone,  forming  a 
communication  between  the  two  inferior  petrosal  sinuses.  Some- 
times there  are  two  sinuses  in  this  situation. 

The  ARTERIES  of  the  dura  mater  are  the  anterior  meningeal, 
from  the  ethmoidal,  ophthalmic,  and  internal  carotid  ;  the  middle 
and  small  meningeal^  from  the  internal  maxillary ;  the  inferior 
iitt'xuigeal,  from  the  ascending  pharyngeal  and  occipital ;  and 
the  posterior  meningeal,  from  the  vertebral. 

If  the  dura  mater  be  stripped  up  in  the  middle  fossa  of  the 
cranium,  the  arteria  meningea  media  will  be  seen  issuing  from  the 
foramen  spinosum  and  dividing  into  two  branches.  The  anterior 
branch  crosses  the  great  ala  of  the  sphenoid  to  the  groove  or  canal 
in  the  anterior  inferior  angle  of  the  parietal  bone,  and  gives  off 
branches  which  ramify  upon  the  external  surface  of  the  duramater, 
and  anastomose  with  corresponding  branches  from  the  opposite 
side.  The  posterior  branch  crosses  the  squamous  portion  of  the 
temporal  bone  torthe  posterior  part  of  the  dura  mater  and  craniuum. 
The  arteria  meningea  media  gives  branches  to  the  Casserian  gan- 
glion and  a  small  branch  which  enters  the  hiatus  Fallopii  to  supply 
the  facial  nerve.  Its  other  branches  are  destined  to  the  bones  of 
the  cranium  and  dura  mater. 

The  NERVES  of  the  dura  mater  are  derived  from  the  sympathetic, 
and  accompany  the  arteries.  Some  filaments  are  also  given  to  it 
by  the  Casserian  ganglion  ;  and  a  large  recurrent  branch  arises 
from  the  ophthalmic,  and  sometimes  from  the  fourth  nerve,  in  the 
cavernous  sinus,  and  takes  its  course  between  the  layers  of  the 
tentorium  to  the  lateral  sinus.  Purkinje  describes  a  nervous 
plexus  as  being  situated  around  the  trunk  of  the  vena  Galeni, 
and  distributing  filaments  to  the  tentorium. 

21* 


246  THE   DISSECTOR. 


SPINAL    CORD. 

The  dissection  of  the  spinal  cord  requires  that  the  spinal  column  should 
be  opened  throughout  its  entire  length  by  sawing  through  the  laminae  of 
the  vertebrae,  close  to  the  roots  of  the  transverse  processes,  and  raising 
the  arches  with  a  chisel ;  the  muscles  of  the  back  having  been  removed 
as  a  preliminary  step. 

The  spinal  column  contains  the  spinal  cord,  or  medulla  spinalis  ; 
the  roots  of  the  spinal  nerves  ;  and  the  membranes  of  the  cord, 
viz  :  the  dura  mater,  arachnoid,  pia  mater,  and  membrana  dentata. 

The  dura  mater  spinalis  (theca  vertebralis)  is  a  cylindrical 
sheath  of  fibrous  membrane,  identical  in  structure  with  the  dura 
mater  of  the  skull,  and  continuous  with  that  membrane.  At  the 
margin  of  the  occipital  foramen  it  is  closely  adherent  to  the  bone  ; 
by  its  anterior  surface  it  is  attached  to  the  posterior  common 
ligament,  and  below,  by  means  of  its  pointed  extremity,  to  the 
coccyx.  In  the  rest  of  its  extent  it  is  comparatively  free,  being 
connected,  by  a  loose  cellular  tissue,  to  the  walls  of  the  spinal 
canal.  In  this  cellular  tissue  there  exists  a  quantity  of  reddish, 
oily,  adipose  substance,  somewhat  analogous  to  the  marrow  of 
long  bones.  On  either  side,  and  below,  the  dura  mater  forms  a 
sheath  for  each  of  the  spinal  nerves,  to  which  it  is  closely  adherent. 
Upon  its  inner  surface  it  is  smooth,  being  lined  by  the  arachnoid  ; 
and  on  its  sides  may  be  seen  double  openings  for  the  two  roots 
of  each  of  the  spinal  nerves. 

The  arachnoid  is  a  continuation  of  the  serous  membrane  of  the 
brain.  It  incloses  the  cord  very  loosely,  being  connected  to  it 
only  by  long  slender  filaments1  of  cellular  tissue,  and  by  a  longi- 
tudinal lamella  which  is  attached  to  the  posterior  aspect  of  the 
cord.  The  cellular  tissue  is  most  abundant  in  the  cervical  region, 
and  diminishes  in  quantity  from  above  downwards ;  and  the 
longitudinal  lamella  is  complete  only  in  the  dorsal  region.  The 
arachnoid  passes  off  from  the  cord  on  either  side  with  the  spinal 
nerves,  to  which  it  forms  a  sheath ;  and  is  then  reflected  on  the 
dura  mater,  to  constitute  its  serous  surface.  A  connection  exists 
in  several  places  between  the  arachnoid  of  the  cord  and  that  of 
the  dura  mater.  The  space  between  the  arachnoid  and  the  spinal 
cord  is  identical  with  that  already  described  as  existing  between 
the  same  parts  in  the  brain,  the  sub-arachnoidean  space.  It  is 
occupied  by  a  serous  fluid,  sufficient  in  quantity  to  expand  the 
arachnoid  and  fill  completely  the  cavity  of  the  theca  vertebralis. 

The  sub-arachnoidean  or  cerebro-spinal  jluid  keeps  up  a  con- 
stant and  gentle  pressure  on  the  entire  surface  of  the  brain  and 

1  According  to  Mr.  Rainey,  these  filaments  are  nervous  fasciculi,  hav- 
ing their  origin  in  the  arachnoid,  and  passing  to  the  arteries  of  the  cord. 
See  p.  208. 


SPINAL  CORD.  247 

spinal  cord,  and  yields  with  the  greatest  facility  to  the  various 
movements  of  the  cord,  giving  to  those  delicate  structures  the 
advantage  of  the  principles  so  usefully  applied  by  Dr.  Arnott  in 
the  hydrostatic  bed. 

The  pia  mater  is  the  immediate  investment  of  the  cord ;  and 
like  the  other  membranes,  is  continuous  with  that  of  the  brain. 
It  is  not,  however,  like  the  pia  mater  cerebri,  a  vascular  mem- 
brane ;  but  is  dense  and  fibrous  in  structure,  and  contains  but 
few  vessels.  It  invests  the  cord  closely,  and  sends  a  duplicature 
into  the  fissura  longitudinalis  anterior,  and  another,  extremely 
delicate,  into  the  fissura  longitudinalis  posterior.  It  forms  a 
sheath  for  each  of  the  filaments  of  the  nerves,  and  for  the  nerves 
themselves  ;  and,  inferiorly,  at  the  conical  termination  of  the  cord, 
is  prolonged  downwards  as  a  slender  ligament  (filum  terminale), 
which  descends  through  the  centre  of  the  cauda  equina,  and  is 
attached  to  the  dura  mater  lining  the  canal  of  the  coccyx.  This 
attachment  is  a  rudiment  of  the  original  extension  of  the  spinal 
cord  into  the  canal  of  the  sacrum  and  coccyx.  The  pia  mater 
has,  distributed  to  it,  a  number  of  nervous  plexuses  derived  from 
the  sympathetic. 

The  membrana  dentata  (ligamentum  dentatum)  is  a  thin  pro- 
cess of  pia  mater  sent  off  from  each  side  of  the  cord  throughout 
its  entire  length,  and  separating  the  anterior  from  the  posterior 
roots  of  the  spinal  nerves.  The  number  of  serrations  on  each 
side  is  about  twenty,  the  first  being  situated  on  a  level  with  the 
occipital  foramen,  and  having  the  vertebral  artery  and  hypoglos- 
sal  nerve  passing  in  front,  and  the  spinal  accessory  nerve  behind 
it,  and  the  last  opposite  the  first  or  second  lumbar  vertebra. 
Below  this  point,  the  merabrana  dentata  is  lost  in  the  filum  ter- 
minale of  the  pia  mater.  The  use  of  this  membrane  is  to  main- 
tain the  position  of  the  spinal  cord  in  the  midst  of  the  fluid  by 
which  it  is  surrounded. 

The  spinal  cord  of  the  adult,  somewhat  less  than  eighteen 
inches  in  length,  extends  from  the  pons  Yarolii  to  opposite  the 
first  or  second  lumbar  vertebra,  where  it  terminates  in  a  rounded 
point;  in  the  child,  at  birth,  it  reaches  the  middle  of  the  third 
lumbar  vertebra,  and  in  the  embryo  is  prolonged  as  far  as  the 
coccyx.  It  presents  a  difference  of  diameter  in  different  parts  of 
its  extent,  and  exhibits  three  enlargements.  The  uppermost  of 
these  is  the  medulla  oblongata ;  the  next  corresponds  with  the 
origin  of  the  nerves  destined  to  the  upper  extremities  (brachial)  ; 
and  the  lower  enlargement  (lumbar)  is  situated  near  its  termina- 
tion, and  corresponds  with  the  attachment  of  the  nerves  which 
are  intended  for  the  supply  of  the  lower  limb.  The  brachial 
enlargement  is  flattened  from  before  backwards,  and  extends 
from  the  third  cervical  vertebra  to  the  first  dorsal  ;  the  lumbar 


248  THE   DISSECTOR. 

enlargement  is  flattened  from  side  to  side,  and  is  smaller  than  the 
brachial.  The  spinal  cord  gives  off  near  its  termination  that 
assemblage  of  nerves  which  has  received  the  name  of  cauda 
equina. 

In  form,  the  spinal  cord  is  a  flattened  cylinder,  and  presents 
on  its  anterior  surface  a  fissure,  which  extends  into  the  cord  to 
the  depth  of  one-third  of  its  diameter.  This  is  the  anterior 
median  fissure.  If  the  sides  of  the  fissure  be  gently  separated, 
they  will  be  seen  to  be  connected  at  the  bottom  by  a  layer  of 
medullary  substance,  the  anterior  white  commissure. 

On  the  posterior  surface  another  fissure  exists,  which  is  so 
narrow  between  the  second  cervical  and  second  lumbar  nerve,  as 
to  be  hardly  perceptible.  This  is  the  posterior  median  fissure. 
It  extends  more  deeply  into  the  cord  than  the  anterior  fissure, 
and  terminates  in  the  gray  substance  of  the  interior.1  These  two 
fissures  divide  the  medulla  spinalis  into  two  lateral  cords,  which 
are  connected  to.  each  other  by  the  white  commissure  which  forms 
the  bottom  of  the  anterior  fissure,  and  by  a  commissure  of  gray 
matter  situated  behind  the  former.  On  either  side  of  the  poste- 
rior median  fissure  is  a  slight  line  which  bounds  on  each  side  the 
posterior  median  columns.  These  columns  are  most  apparent  at 
the  uppert  part  of  the  cord,  in  the  medulla  oblongata,  where 
they  have  received  the  name  of  posterior  pyramids. 

Two  other  lines  are  observed  on  the  medulla,  the  anterior  and 
posterior  lateral  sulci,  corresponding  with  the  attachment  of  the 
anterior  and  posterior  roots  of  the  spinal  nerves.  The  anterior 
lateral  sulcus  is  a  mere  trace,  marked  only  by  the  attachments  of 
the  filaments  of  the  anterior  roots.  The  posterior  lateral  sulcus 
is  more  evident,  and  is  a  narrow  grayish  line,  derived  from  the 
grayish  substance  of  the  interior. 

Although  these  fissures  and  sulci  indicate  a  division  of  the 
spinal  cord  into  three  pairs  of  columns,  namely,  anterior,  lateral, 
and  posterior,  the  posterior  median  columns  being  regarded  as  a 
part  of  the  posterior  columns,  it  is  customary  to  consider  each 
half  of  the  spinal  cord  as  consisting  of  two  columns  only,  the 
antero-lateral  and  the  posterior.  The  antero-lateral  columns  are 
the  columns  of  motion,  and  comprehend  all  that  part  of  the  cord 
situated  between  the  fissura  longitudinalis  anterior  and  the  pos- 
terior lateral  sulcus,  the  gray  line  of  origin  of  the  posterior  roots 
of  the  spinal  nerves.  The  posterior  columns  are  the  columns  of 
sensation. 

If  a  transverse  section  of  the  spinal  cord  be  made,  its  internal 
structure  may  be  seen  and  examined.  It  will  then  appear  to  be 

1  According  to  some  anatomists,  there  exists  a  posterior  white  commis- 
sure at  the  bottom  of  the  posterior  median  fissure. 


SPINAL  CORD.  249 

composed  of  two  hollow  cylinders  of  white  matter,  placed  side 
by  side,  and  connected  by  a  narrow  white  commissure.  Each 
cylinder  is  filled  with  gray  substance,  which  is  connected  by  a 
commissure  of  the  same  matter  (gray  commissure).  The  form  of 
the  gray  substance,  as  obseryed  in  the  section,  is  that  of  two 
irregularly  curved  or  crescentic  lines  joined  by  a  transverse  band. 

Fig.  76. 


SECTION  OF  THE  SPINAL  CORD  WITH  ITS  MEMBRANES. — 1.  The  dura  mater. 
2,  2.  The  dura  mater,  forming  a  sheath  for  each  of  the  roots  of  a  spinal  nerve, 
and  afterwards  a  sheath  for  the  nerve  itself.  The  dotted  line  represents  the 
:ir;trhnoid  membrane.  3,  3.  A  sheath  formed  by  the  arachnoid  around  each  of 
the  roots  of  the  spinal  nerve  during  its  passage  through  that  membrane.  4.  The 
space  between  the  two  layers  of  the  arachnoid  ;  an  arrow  at  each  side  shows  that 
this  space  is  continuous  all  around  the  spinal  cord,  and  that  the  disposition  of 
the  membrane  at  3,  3,  is  a  mere  sheath.  5.  The  space  between  the  arachnoid 
and  pia  mater,  the  sub-arachnoidean  space,  in  which  is  lodged  the  sub-arach- 
noidean  fluid.  6.  One  of  the  dentations  of  the  ligamentum  denticulatum.  7,  7. 
The  pia  mater  of  the  cord.  8.  The  sulcus  longitudinalis.  9.  The  white  com- 
missure, connecting  the  two  lateral  halves  of  the  cord.  10.  The  gray  commissure, 
connecting  the  two  semilunar  processes  of  gray  substance.  11.  The  sulcus  longi- 
tudinalis posterior.  12,  12.  The  two  anterior  or  motor  columns  of  the  spinal  cord. 
13, 13.  The  two  lateral  columns.  14,  14.  The  two  posterior  or  sensitive  columns. 
15,  15.  The  posterior  median  columns,  bounded  by  two  shallow  fissures.  16. 
The  origin  of  the  anterior  or  motor  root  of  a  spinal  nerve.  17.  The  origin  of  its 
posterior  or  sensitive  root.  18.  The  ganglion  on  the  posterior  root.  19.  The 
spinal  nerve  dividing  into  its  two  primary  branches,  anterior  and  posterior. 

The  extremities  of  the  curved  lines  correspond  with  the  sulci  of 
origin  of  the  anterior  and  posterior  roots  of  the  nerves.  The 
anterior  extremities,  larger  than  the  posterior,  do  not  quite  reach 
this  surface ;  but  the  posterior  appear  upon  the  surface,  and  form 
a  narrow  gray  line,  the  sulcus  lateralis  posterior. 

The  white  substance  of  the  spinal  cord  is  composed  of  parallel  fibres, 
which  are  collected  into  longitudinal  laminae  and  extend  throughout  the 
entire  length  of  the  cora.  These  laminae  are  various  in  breadth,  and  are 
arranged  in  a  radiated  manner  ;  one  border  being  thick  and  corresponding 
with  the  surface  of  the  cord,  while  the  other  is  thin  and  lies  in  contact 
with  the  gray  substance  of  the  interior.  According  to  Rolando,  the  white 
substance  constitutes  a  simple  nervous  membrane,  which  is  folded  into 


250  THE   DISSECTOR. 

longitudinal  plaits,  having  the'  radiated  disposition  above  described.  The 
anterior  commissure,  according  to  his  description,  is  merely  the  continu- 
ation of  this  nervous  membrane  from  one  lateral  cord  across  the  middle 
line  to  the  other.  Moreover,  Rolando  considers  that  a  thin  lamina  of  pia 
mater  is  received  between  each  of  the  folds  from  the  exterior,  while  a 
layer  of  the  gray  substance  is  prolonged  between  them  from  within. 
Cruveilhier  is  of  opinion  that  each  lamella  is  completely  independent  of 
its  neighbors,  and  he  believes  this  statement  to  be  confirmed  by  patho- 
logy, which  shows  that  a  single  lamella  may  be  injured  or  atrophied,  and 
at  the  same  time  be  surrounded  by  others  perfectly  sound. 

SPINAL  NERVES. — The  nerves  proceeding  from  the  spinal  cord 
are  thirty-one  pairs.  Each  nerve  arises  by  two  roots,  an  anterior 
or  motor  root,  and  a  posterior  or  sensitive  root. 

The  anterior  roots  proceed  from  a  narrow  white  line,  anterior 
lateral  sulcus,  on  the  antero-lateral  column  of  the  spinal  cord,  and 
gradually  approach  towards  the  anterior  median  fissure  as  they 
descend. 

The  posterior  roots,  more  regular  than  the  anterior,  proceed 
from  the  posterior  lateral  sulcus,  a  narrow  gray  stria  formed  by 
the  internal  gray  substance  of  the  cord.  They  are  larger,  and 
the  filaments  of  origin  more  numerous  than  those  of  the  anterior 
roots.  In  the  intervertebral  foramina  there  is  a  ganglion  on  each 
of  the  posterior  roots.  The  first  cervical  nerve  forms  an  exception 
to  these  characters  ;  its  posterior  root  is  smaller  than  the  anterior ; 
it  often  joins  in  whole  or  in  part  with  the  spinal  accessory  nerve, 
and  sometimes  with  the  hypoglossal :  there  is  frequently  no  gan- 
glion upon  it,  and  when  the  ganglion  exists,  it  is  often  situated 
within  the  dura  mater,  the  latter  being  the  usual  position  of  the 
ganglia  of  the  last  two  pairs  of  spinal  nerves. 

After  the  formation  of  a  ganglion,  the  two  roots  unite,  and 
constitute  a  spinal  nerve,  which  escapes  through  the  interverte- 
bral foramen,  and  separates  into  an  anterior  division  for  the  sup- 
ply of  the  front  aspect  of  the  body,  and  a  posterior  division  for 
the  posterior  aspect.  In  the  first  cervical  and  last  sacral  and 
coccygeal  nerve  this  separation  takes  place  within  the  dura  mater, 
and  in  the  upper  four  sacral  nerves  externally  to  that  cavity,  but 
within  the  sacral  canal.  The  anterior  divisions,  with  the  excep- 
tion of  the  first  two  cervical  nerves,  are  larger  than  the  poste- 
rior; an  arrangement  which  is  proportioned  to  the  large  extent 
of  surface  they  are  required  to  supply. 

The  spinal  nerves  are  classed  as  follows: — 

Cervical        .        /.       ..      -VJ*.  -    8  pairs. 
Dorsal      =^  ' './'.>      ,         .     12     " 
Lumbar       .     &%'*       „>       .       5     " 
Sacral          .      -  .»•  . -'.-  :     .       5     " 
Coccygeal    .         .         .         .1  pair. 


SPINAL   NERVES.  251 

The  cervical  nerves  pass  off  transversely  from  the  spinal  cord ; 
the  dorsal  are  oblique  in  their  direction ;  and  the  lumbar  and 
sacral,  vertical ;  the  latter  form  the  large  assemblage  of  nerves 
at  the  termination  of  the  cord,  called  cauda  equina.  The  cauda 
equina  occupies  the  lower  third  of  the  spinal  canal. 

The  ARTERIES  of  the  spinal  cord  are,  the  anterior,  posterior, 
and  lateral  spinal,  which  are  derived  from  the  vertebral;  and 
branches  from  the  intercostal  and  lumbar  arteries,  which  enter 
the  canal  through  the  intervertebral  foramina. 

The  VEINS  of  the  vertebral  column  and  spinal  cord  form  a 
complex  venous  plexus  within  and  around  the  vertebral  canal, 
and  are  divisible  into  three  sets  : — 
Dorsi-spinal, 
Meningo-rachidian, 
Medulli-spinal. 

The  dorsi-spinal  form  a  plexus  around  the  spinous,  transverse 
and  articular  processes  and  arches  of  the  vertebrae  They  re- 
ceive the  returning  blood  from  the  dorsal  muscles  and  surround- 
ing structures,  and  transmit  it,  in  part  to  the  meningo-rachidian, 
and  in  part  to  the  vertebral,  intercostal,  lumbar,  and  sacral 
veins. 

The  meningo-rachidian  veins  are  situated  between  the  theca 
vertebralis  and  the  vertebrae.  They  communicate  freely  with 
each  other  by  means  of  a  complicated  plexus.  In  front,  they 
form  two  longitudinal  trunks  (longitudinal  spinal  sinuses),  which 
extend  the  whole  length  of  the  column,  one  on  each  side  of  the 
posterior  common  ligament,  and  are  joined  on  the  body  of  each 
vertebra  by  transverse  trunks,  which  pass  beneath  the  ligament, 
and  receive  the  large  basi-vertebral  veins  from  the  interior  of  each 
vertebra.  The  meningo-rachidian  veins  communicate  superiorly 
through  the  anterior  condyloid  foramina  with  the  internal  jugu- 
lars ;  in  the  neck  they  pour  their  blood  into  the  vertebral  veins ; 
in  the  thorax,  into  the  intercostals;  and  in  the  loins  and  pelvis 
into  the  lumbar  and  sacral  veins,  the  communications  being  esta- 
blished through  the  intervertebral  foramina. 

The  medutti-spinal  veins  are  situated  between  the  pia  mater 
and  arachnoid;  they  communicate  freely  with  each  other  to  form 
plexuses,  and  send  branches  through  the  intervertebral  foramina 
with  each  of  the  spinal  nerves,  to  join  the  veins  of  -the  trunk. 


252  THE   DISSECTOR. 


CHAPTER    V. 

ORGANS  OF  SENSE. 

The  Nose  and  Nasal  Fossce. 

THE  organ  of  smell  consists  essentially  of  two  parts:  one  ex- 
ternal, the  nose;  the  other  internal,  the  nasal  fossce. 

The  dissection  of  the  nose  and  nasal  fossae  is  to  be  made  on  that  piece 
of  the  face  which  has  been  already  used  in  the  examination  of  the 
pharynx  and  soft  palate  (pp.  196,  198).  If  the  cartilages  of  the  nose  be 
dry,  they  should  be  softened  by  steeping  in  water  and  brought  into  a 
state  fit  for  dissection.  Any  integument  which  may  have  been  left  on 
the  nose  should  then  be  removed,  together  with  cellular  tissue,  fat,  and 
the  remains  of  muscles.  The  dissection  will  be  facilitated  by  stuffing 
the  nostrils  with  cotton  wool. 

The  NOSE  is  the  triangular  pyramid  projecting  from  the  centre 
of  the  face,  immediately  above  the  upper  lip.  Superiorly,  it  is 
connected  with  the  forehead,  by  means  of  a  narrow  bridge;  in- 
feriorly,  it  presents  two  openings,  the  nostrils,  which  overhang 
the  mouth,  and  are  so  constructed  that  the  odor  of  all  substances 
must  be  received  by  the  nose,  before  they  can  be  introduced 
within  the  lips.  The  septum  between  the  openings  of  the  nos- 
trils is  called  the  columna.  Their  entrance  is  guarded  by  a  num- 
ber of  stiff  hairs  (vibrissce),  which  project  across  the  openings, 
and  act  as  a  filter  in  preventing  the  introduction  of  foreign  sub- 
stances, such  as  dust,  or  insects,  with  the  current  of  air  intended 
for  respiration. 

The  anatomical  elements  of  wliich  the  nose  is  composed,  are — 
1.  The  integument;  2.  Muscles;  3.  Bones;  4.  Fibro-cartilages  ; 
5.  Mucous  membrane ;  6.  Vessels  and  nerves. 

1.  The  integument  forming  the  tip  (lobulus),  and  wings  (alee], 
of  the  nose  is  extremely  thick  and  dense,  so  as  to  be  with  diffi- 
culty separated  from  the  fibro-cartilage.  It  is  furnished  with  an 
abundance  of  sebaceous  follicles,  which,  by  their  oily  secretion, 
protect  the  extremity  of  the  nose  in  excessive  alternations  of 
temperature.  The  sebaceous  matter  of  these  follicles  becomes 
of  a  dark  color  near  the  surface,  from  altered  secretion  and  also 
from  attraction  of  the  carbonaceous  matter  floating  in  the  atmo- 
sphere :  hence  the  spotted  appearance  which  the  tip  of  the  nose 
presents  in  large  cities.  When  the  integument  is  firmly  com- 


THE   NOSE.  253 

pressed,  the  inspissated  sebaceous  secretion  is  squeezed  out  from 
the  follicles,  and,  taking  the  cylindrical  form  of  their  excretory 
ducts,  has  the  appearance  of  small  white  maggots  with  black 
heads. 

2.  The  muscles  are  brought  into  view  by  reflecting  the  integu- 
ment ;  they  are — the  pyramidalis  nasi,  compressor  nasi,  dilator 
naris,  levator  labii  superioris  ala3que  nasi,  and  depressor  labii 
superioris  alaeque  nasi.     They  have  been  already  described  with 
the  muscles  of  the  face. 

3.  The  bones  of  the  nose  are — the  nasal,  and  nasal  processes 
of  the  superior  maxillary. 

4.  The  Jibro-cartilages  give  form  and  stability  to  the  outwork 
of  the  nose,  providing,  at  the  same  time,  by  their  elasticity, 
against  injuries.     They  are  five  in  number,  namely,  the — 

Fibro-cartilage  of  the  septum, 
T\vo  lateral  fibro-cartilages, 
Two  alar  fibro-cartilages. 

The  Jibro-cartikige  of  the  septum,  somewhat  triangular  in  form, 
divides  the  nose  into  its  two  nostrils.  It  is  connected  above 
with  the  nasal  bones  and  lateral  fibro-cartilages ;  behind,  with 
the  ethmoidal  septum  and  vomer;  and  below,  with  the  palate 
processes  of  the  superior  maxillary  bones.  The  alar  fibro-carti- 
lages and  columna  move  freely  upon  the  fibre-cartilage  of  the 
septum,  being  but  loosely  connected  with  it  by  perichondrium. 

The  IiitiTfil  Jibro-cartilages  are  also  triangular  ;  they  are  con- 
nected, in  front,  with  the  fibro-cartilage  of  the  septum ;  above, 
with  the  nasal  bones  ;  behind,  with  the  nasal  processes  of  the 
superior  maxillary  bones  ;  and  below,  with  the  alar  fibro-carti- 
lages. 

Alar  Jibro-cartilages. — Each  of  these  cartilages  is  curved  in 
such  a  manner  as  to  correspond  with  the  walls  of  the  nostril,  to 
which  it  forms  a  kind  of  rim.  The  inner  portion  is  loosely  con- 
nected with  the  same  part  of  the  opposite  cartilage,  so  as  to 
form  the  columna.  It  is  expanded  and  thickened  at  the  point 
of  the  nose  to  constitute  the  lobe  ;  and  on  the  side  makes  a  curve 
corresponding  with  that  of  the  ala.  This  curve  is  prolonged 
downwards  and  forwards  in  the  direction  of  the  posterior  border 
of  the  ala  by  three  or  four  small  fibro-cartilaginous  plates  (sesa- 
moid  cartilages,  cartilagines  minores),  which  are  appendages  of 
the  alar  fibro-cartilage. 

The  whole  of  these  fibro-cartilages  are  connected  with  each 
other  and  to  the  bones  by  perichondrinm,  which,  from  its  mem- 
branous structure,  permits  of  the  freedom  of  motion  existing 
between  them. 

5.  The  mucous  membrane,  lining  the  interior  of  the  nose,  is 
22 


254  THE   DISSECTOR. 

continuous  with  the  skin  externally,  and  with  the  pituitary  mem- 
brane of  the  nasal  fossae  within.  Around  the  entrance  of  the 
nostrils  it  is  provided  with  the  vibrissce. 

Fig.  77. 


VIEW  or  THE  BONES  AND  CARTI-  FRONT  VIEW  OP  THE  CARTI- 
LAGES OF  THE  OUTER  NOSE,  FROM  LAGES  OF  THE  NOSE. — Above  is 
THE  RIGHT  SIDE. — a.  Nasal  bone.  seen  the  outline  of  the  nasal  bones. 
b.  Nasal  process  of  upper  maxillary  — a.  Front  edge  of  the  septal  car- 
bone.  1.  Right  upper  lateral  car-  tilage.  b,  b.  Lateral  cartilages,  c,  c. 
tilage.  2.  Lower  lateral  cartilage,  Alar  cartilages,  with  their  append- 
its  outer  part.  2*.  Innjer  part  of  ages. 
the  same.  3.  Sesamoid  cartilages. 

6.  Vessels  and  Nerves. — The  arteries  of  the  nose  are  the  late- 
ralis  nasi  from  the  facial,  and  nasalis  septi  from  the  superior 
coronary. 

Its  nerves  are  the  facial,  infra-orbital,  and  nasal  branch  of  the 
ophthalmic. 

NASAL  FOSSAE. 

To  obtain  a  view  of  the  nasal  fossce,  the  face  must  be  divided  through 
the  nose  by  a  vertical  incision  a  little  to  one  side  of  the  middle  line. 
This  incision  should  be  made  with  the  scalpel  through  the  nose,  and 
with  the  saw  through  one  nasal  bone,  the  frontal  bone,  the  cribriform 
plate  of  the  ethmoidal,  and  body  of  the  sphenoid  above ;  and  through  the 
palatal  process  of  the  superior  maxillary  and  palate  bone  bdow.  When 
the  section  is  made,  the  turbinated  bones,  with  the  spaces  between  them, 
will  be  exposed  on  one  side,  and  the  septum  narium  on  the  other ;  both 
are  covered  by  mucous  membrane. 

The  nasal  fossae  are  two  irregular,  compressed  cavities,  extend- 
ing backwards  from  the  nose  to  the  pharynx.  They  are  bounded 
superiorly  by  the  lateral  cartilage  of  the  nose,  and  by  the  nasal, 
sphenoid,  and  ethmoid  bones  ;  inferiorly  by  the  hard  palate ; 


NASAL  VOB8JE.  255 

and,  in  the  middle  line,  they  are  separated  from  each  other  by  a 
bony  and  fibre-cartilaginous  septum. 

Upon  the  outer  wall  of  each  fossa,  in  the  dried  skull,  are  three 
projecting  processes,  termed  spongy  bones.  The  two  superior 
belong  to  the  ethmoid  ;  the  inferior  is  a  separate  bone.  In  the 
fresh  fossae  these  are  covered  with  mucous  membrane,  and  serve 
to  increase  the  surface  of  that  membrane  by  their  prominence 
and  convoluted  form.  The  space  intervening  between  the  supe- 
rior and  middle  spongy  bone  is  the  superior  meatus  ;  the  space 
between  the  middle  and  inferior,  the  middle  meatus ;  and  that 
between  the  inferior  and  the  floor  of  the  fossa,  the  inferior  mea- 
tus. 

These  meatuses  are  passages  which  extend  from  before  back- 
wards, and  it  is  in  circulating  through  and  amongst  these  that 
the  atmosphere  deposits  its  odorant  particles  upon  the  mucous 

Fig.  79. 


THE  OUTER  WALL  OP  THE  LEFT  NASAL  FOSSA  COVERED  WITH  THE  PITUI- 
TARY MEMBRANE. — 1.  Frontal  bone.  2.  Nasal  bone.  3.  Superior  maxillary. 
4.  Sphenoid.  5.  The  upper  spongy  bone.  6.  Middle  spongy  bone.  7.  Lower 
spongy  bone.  The  three  meatuses  of  the  nose  are  seen  below  the  three  last- 
named  bones.  8.  The  opening  of  the  Eustachian  tube.  9  is  beneath  the  open- 
ing of  the  nasal  duct. 

membrane.  There  are  several  openings  into  the  nasal  fossae  : 
thus,  in  the  superior  meatus  are  the  openings  of  the  sphenoidal 
and  posterior  ethmoidal  cells ;  in  the  middle  the  anterior  eth- 
moidal  cells,  the  frontal  sinuses,  and  the  antrum  maxillare ;  and, 


256  THE   DISSECTOR. 

in  the  inferior  raeatus,  the  termination  of  the  nasal  duct.  In  the 
dried  bone  there  are  two  additional  openings,  the  spheno-pala- 
tine  and  the  anterior  palatine  foramen  ;  the  former  being  situated 
in  the  superior,  and  the  latter  in  the  inferior  meatus. 

The  mucous  membrane  of  the  nasal  fossae  is  called  pituitary,  or 
Schneiderian ;  the  former  name  being  derived  from  the  nature  of 
its  secretion,  the  latter  from  Schneider,  who  was  the  first  to  show 
that  the  secretion  of  the  nose  proceeded  from  the  mucous  mem- 
brane, and  not  from  the  brain,  as  was  formerly  imagined.  It  is 
closely  adherent  to  the  periosteum,  constituting  what  is  called  a 
fibro-mucous  membrane,  and  is  continuous  with  the  general 
gastro-pulmonary  mucous  membrane.  From  the  nasal  fossae  it 
may  be  traced  through  the  openings  in  the  meatuses,  into  the 
sphenoidal  and  ethmoidal  cells;  into  the  frontal  sinuses;  into 
the  antrum  maxillare;  through  the  nasal  duct  to  the  surface  of 
the  eye,  where  it  is  continuous  with  the  conjunctiva;  along  the 
Eustachian  tubes  into  the  tympanum  and  mastoid  cells,  to  which 
it  forms  the  lining  membrane  ;  and  through  the  posterior  nares 
into  the  pharynx  and  mouth,  and  thence  through  the  lungs  and 
alimentary  canal. 

The  surface  of  the  membrane  is  furnished  with  a  laminated 
epithelium  near  the  apertures  of  the  nares,  and  in  the  rest  of  its 
extent  with  a  columnar  epithelium  supporting  innumerable  vibra- 
tile  cilia. 

The  ARTERIES  of  the  nasal  fossae  are  the  anterior  and  posterior 
ethmoidal  and  spheno-palatine. 

The  ethmoidal  arteries  are  branches  of  the  ophthalmic,  and 
enter  the  nasal  fossae  through  the  foramina  in  the  cribriform 
plate.  They  supply  the  mucous  membrane  of  the  upper  part  of 
the  fossae. 

The  spheno-palatine  artery  is  a  branch  of  the  internal  maxillary. 
It  enters  the  nasal  fossae  with  the  nasal  nerves  through  the  spheno- 
palatine  foramen  at  the  posterior  part  of  the  superior  meatus, 
and  divides  into  several  branches  which  are  distributed  to  the 
mucous  membrane  of  the  spongy  bones,  posterior  ethmoidal  cells, 
and  antrum.  One  branch,  the  artery  of  the  septum,  crosses  the 
roof  of  the  fossa,  and  passes  downwards  and  forwards  beneath 
the  mucous  membrane  of  the  septum  to  the  anterior  palatine 
canal,  where  it  inosculates  with  branches  of  the  descending  pala- 
tine artery. 

The  NERVES  of  the  nose  and  nasal  fossae  are  the  olfactory,  the 
nasal  and  naso-palatine  from  Meckel's  ganglion,  and  the  nasal 
branch  of  the  ophthalmic. 

The  olfactory  nerve  is  distributed  to  the  mucous  membrane  of 
the  nasal  fossae  by  means  of  a  number  of  branches  which  pass 
through  the  foramina  in  the  cribriform  plate  of  the  ethmoid  bone. 


NERVES  OF  THE   NOSE.  257 

The  branches  are  arranged  in  three  groups,  an  inner  group,  red- 
dish in  color  and  soft,  spread  out  upon  the  upper  part  of  the 
septum ;  an  outer  group,  whiter  and  more  firm,  which  descend 
through  bony  canals  in  the  outer  wall  of  the  nares,  and  are  dis- 
tributed on  the  superior  and  middle  spongy  bones  ;  and  a  middle 
group,  which  supply  the  mucous  membrane  of  the  roof  of  the 
nasal  fossae. 

The  nasal  branches  of  MeckePs  ganglion  enter  the  nasal  fossaB 
through  the  spheno-palatine  foramen,  and  are  distributed  to  the 
mucous  membrane  of  the  superior  and  middle  spongy  bones,  the 
posterior  ethmoidal  cells,  and  the  upper  part  of  the  septum. 

The  naso-palatine  nerve,  also  a  branch  of  Meckel's  ganglion, 
enters  the  nasal  fossae  with  the  nasal  nerves,  and,  crossing  the 
roof  of  the  fossae,  descends  upon  the  septum  beneath  the  mucous 
membrane  to  the  naso-palatine  canal.  Passing  through  the  naso- 
palatine  canal,  it  enters  the  anterior  palatine  canal,  and  is  distri- 
buted to  the  papilla  behind  the  incisor  teeth,  communicating  with 
its  fellow  of  the  opposite  side  and  with  the  anterior  palatine 
nerves.  In  its  course  the  naso-palatine  nerve  gives  several 
branches  to  the  raucous  membrane  of  the  septum ;  and  the  naso- 
palatine  canal  of  the  left  side  is  in  front  of  that  of  the  right. 

The  naso-palatine  nerve,  and  also  the  inner  group  of  branches  of  the 
olfactory,  are  best  seen  by  cutting  away  the  osseous  portion  of  the  septum, 
and  tearing  it  away  from  the  mucous  membrane.  Before  this  is  done, 
the  extent  and  relations  of  the  cartilage  of  the  septum  should  be  examined. 
The  outer  group  of  branches  of  the  olfactory  nerve  are  to  be  sought  for  on 
the  outer  wall  of  the  nasal  fossae,  and  the  nasal  branch  of  the  ophthalmic 
on  the  anterior  part  of  its  roof  beneath  the  nasal  bone. 

The  nasal  branch  of  the  ophthalmic  nerve  enters  the  nasal  fossae 
by  the  most  anterior  of  the  openings  in  the  cribriform  plate  of  the 
ethmoid  bone,  and  divides  into  an  internal  and  external  branch. 
The  internal  branch  is  distributed  to  the  mucous  membrane  of  the 
septum  as  far  as  the  aperture  of  the  nostril.  The  external  branch 
continues  its  course  onwards,  in  a  groove,  upon  the  under  surface 
of  the  nasal  bone,  passes  between  the  nasal  bone  and  lateral  car- 
tilage, and  is  distributed  to  the  exterior  of  the  nose,  as  far  as  the 
aperture  of  the  nostril.  In  the  nasal  fossae  this  branch  gives  off 
several  filaments  to  the  internal  surface  of  the  outer  wall  of  the 
nose. 

Practical  Observations. — The  mucous  membrane  is  rendered  an  organ 
of  smell  by  contact  of  the  odorant  particles.  If  the  secretion  be  deficient, 
the  contact  is  not  appreciable,  and  there  is  loss  of  smell.  Or  if  the 
membrane  be  swollen  and  thickened,  there  is  likewise  loss  of  smell. 
Both  of  these  conditions  are  consequences  of  common  cold. 

When  hemorrhage  occurs  from  the  mucous  membrane,  it  may  proceed 
to  so  great  an  extent  as  to  endanger  life.  In  such  a  case  the  nasal  fossae 
must  be  stopped  from  behind,  by  drawing  a  piece  of  sponge  against  the 
posterior  nares.  This  is  effected  by  introducing  an  instrument  carrying 

22* 


258  THE   DISSECTOR. 

a  curved  spring  with  an  eye  at  its  extremity  along  the  inferior  meatus 
to  the  pharynx.  The  spring  is  then  pressed  onwards,  and  is  directed  by 
its  curve  into  the  posterior  part  of  the  mouth ;  the  thread  bearing  the 
sponge  is  passed  through  the  eye  of  the  spring,  and  the  instrument  with 
the  thread  is  withdrawn  through  the  nose.  The  sponge  is  then  carefully 
directed  beneath  the  soft  palate,  and  drawn  gently  against  the  posterior 
openings  of  the  nose. 

Growths  of  various  kinds  (polypi)  proceed  from  the  mucous  membrane, 
and  increase  to  a  great  size,  impeding  nasal  respiration,  forcing  the  bones 
out  of  their  places,  and  doing  great  mischief.  They  are  generally  attached 
by  a  narrow  pedicle,  and  may  be  removed  with  the  polypus  forceps.  In 
performing  this  operation,  the  direction  of  the  meatuses  must  be  recol- 
lected ;  otherwise  there  would  be  danger  of  entangling  the  instrument, 
and  pulling  away  one  of  the  spongy  bones. 

When  the  tube  of  the  stomach-pump  cannot  be  passed  through  the 
mouth,  it  may  be  introduced  into  that  viscus  by  passing  it  along  the 
inferior  meatus  of  the  nose.  Patients  with  extensive  injury  to  the  jaws 
have  been  nourished  for  a  long  time  solely  by  liquid  food  poured  into 
the  stomach  in  this  way. 

In  obstruction  of  the  nasal  duct,  it  is  often  necessary  to  introduce  a 
probe  into  it  from  the  inferior  meatus.  This  operation  should  therefore 
be  practised  upon  the  subject. 

THE  EYE,  WITH  ITS   APPENDAGES. 

The  appendages  of  the  eye.  consisting  of  the  eyelids,  conjunctiva,  and 
lachrymal  apparatus,  are  to  be  examined  from  the  exterior ;  and  the  dis- 
section necessary  for  the  purpose  may  be  made  either  during  the  progress 
of  the  dissection  of  the  face  or  at  a  later  period,  for  example,  after  the 
examination  of  the  nose,  one  orbit  being  reserved  for  the  purpose.  To 
expose  the  tarsal  cartilages,  all  that  is  necessary  is  to  remove  the  orbicu- 
laris  palpebrarum  muscle.  To  reach  the  lachrymal  gland,  and  study  the 
lachrymal  canals  and  nasal  duct,  the  eyelids  must  be  separated  from 
their  connections  above  and  below,  and  turned  inwards. 

The  appendages  of  the  eye  (tutamina  oculi)  are,  the  eyebrows, 
eyelids,  eyelashes,  conjunctiva,  caruncula  lachrymalis,  and  the 
lachrymal  apparatus. 

The  EYEBROWS  (supercilid)  are  two  projecting  arches  of  integ- 
ument, covered  with  short  thick  hairs,  which  form  the  upper 
boundary  of  the  orbits.  They  are  connected  beneath  with  the 
orliicularis,  occipito-frontales,  and  corrugatores  superciliorum 
muscles  ;  their  use  is  to  shade  the  eyes  from  too  vivid  a  light,  or 
protect  them  from  particles  of  dust  and  moisture  floating  over 
the  forehead. 

The  EYELIDS  (palpelrce)  are  two  valvular  layers  placed  in  front 
of  the  eye,  serving  to  defend  it  from  injury  by  their  closure.  When 
drawn  open,  they  leave  between  them  an  elliptical  space  (fissura 
palpebrarum),  the  angles  of  which  are  called  canthi.  The  outer 
canthus  is  formed  by  the  meeting  of  the  two  lids  at  an  acute 
angle.  The  inner  canthus  is  prolonged  for  a  short  distance  in- 
wards, towards  the  nose,  and  a  triangular  space  is  left  between 
the  lids  in  this  situation,  which  is  called  the  lac,us  lachrymalis. 


EYELIDS.  —  MEIBOMTAN   GLANDS.  259 

At  the  commencement  of  the  lacus  lachrymalis,  upon  each  of  the 
two  lids,  is  a  small  angular  projection,  the  lachrymal  papilla  or 
tubercle  ;  and  at  the  apex  of  each  papilla  a  small  orifice  (punctum 
lachrymale),  the  commencement  of  the  lachrymal  canal. 

The  eyelids  have,  entering  into  their  structure,  integument, 
orbicularis  muscle,  tarsal  cartilages,  Meibomian  glands,  and  con- 
junctiva. 

The  tegumentary  cellular  tissue  of  the  eyelids  is  remarkable  for 
its  looseness,  and  for  the  absence  of  adipose  substance  ;  it  is  par- 
ticularly liable  to  serous  infiltration.  The  fibres  of  the  orbicu- 
laris muscle  covering  the  eyelids  are  extremely  thin  and  pale. 

The  tarsal  cartilages  are  two  thin  lamella  of  fibro-cartilage, 
about  an  inch  in  length,  which  give  form  and  support  to  the  eye- 
lids. The  superior  is  of  a  semilunar  form,  about  one-third  of  an 
inch  in  breadth  at  its  middle,  and  tapering  to  each  extremity. 
Its  lower  border  is  broad  and  flat  ;  its  upper  is  thin,  and  gives 
jittachment  to  the  levator  palpebra3  and  to  the  fibrous  membrane 
of  the  lids. 

The  inferior  Jibro-cartilage  is  an  elliptical  band,  narrower  than 
the  superior,  and  situated  in  the  substance  of  the  lower  lid.  Its 
upper  border  is  flat,  and  corresponds  with  the  flat  edge  of  the 
upper  cartilage.  The  lower  is  held  in  its  place  by  the  fibrous 
membrane.  Near  the  inner  canthus  the  tarsal  cartilages  termi- 
nate, at  the  commencement  of  the  lacus  lachrymalis,  and  are 
attached  to  the  margin  of  the  orbit  by  the  tendo  oculi.  At  their 
outer  extremity  they  terminate  at  a  short  distance  from  the  angle 
of  the  canthus,  and  are  retained  in  their  position  by  means  of  a 
decussation  of  the  fibrous  structure  of  the  broad  tarsal  ligament, 
called  the  external  palpebral  or  tarsal  ligament. 

The  fibrous  membrane  of  the  lids  is  firmly  attached  to  the 
periosteum,  around  the  margin  of  the  orbit,  by  its  circumference, 
and  to  the  tarsal  cartilages  by  its  central  margin.  It  is  thick  and 
dense  on  the  outer  half  of  the  orbit,  but  becomes  thin  to  its  inner 
side.  Its  use  is  to  retain  the  tarsal  cartilages  in  their  place,  and 
give  support  to  the  lids  ;  hence  it  has  been  named  the  broad 


The  Meibomian  glands  are  imbedded  in  the  internal  surface  of 
the  cartilages,  and  are  very  distinctly  seen  on  examining  the  inner 
aspect  of  the  lids.  They  have  the  appearance  of  parallel  strings 
of  penrls,  about  thirty  in  number  in  the  upper  cartilage,  and 
somewhat  fewer  in  the  lower;  and  open  by  minute  foramina  on 
the  edges  of  the  lids.  They  correspond  in  length  with  the  breadth 
of  the  cartilage,  and  are  consequently  longer  in  the  upper  than 
in  the  lower  lid. 

Each  gland  consists  of  a  single  lengthened  follicle  or  tube,  into 
which  a  number  of  small  clustered  follicles  open  ;  the  latter  are 


260  THE   DISSECTOR. 

so  numerous  as  almost  to  conceal  the  tube  by  which  the  secretion 
is  poured  out  upon  the  margin  of  the  lids.  Occasionally  an  arch 
is  formed  between  two  of  them,  and  produces  a  very  graceful 
appearance. 

The  edges  of  the  eyelids  are  furnished  with  a  triple  row  of 
long  thick  hairs,  which  curve  upwards  from  the  upper  lid,  and 
downwards  from  the  lower,  so  that  they  may  not  interlace  with 
each  other  in  the  closure  of  the  eyelids,  and  prove  an  impediment 
to  the  opening  of  the  eyes.  These  are  the  eyelashes  (cilia),  im- 
portant organs  of  defence  to  the  sensitive  surface  of  so  delicate 
an  organ  as  the  eye. 

The  conjunctiva  is  the  mucous  membrane  of  the  eye.  It  covers 
the  whole  of  its  anterior  surface,  and  is  then  reflected  upon  the 
lids  so  as  to  form  their  internal  layer.  The  duplicatures  formed 
between  the  globe  of  the  eye  and  the  lids,  are  called  the  superior 
and  inferior  palpebral  sinuses,  of  which  the  former  is  much  deeper 
than  the  inferior.  Where  it  covers  the  cornea  the  conjunctiva  is 
very  thin,  and  closely  adherent,  and  no  vessels  can  be  traced  into 
it.  Upon  the  sclerotica  it  is  thicker,  and  less  adherent;  but 
upon  the  inner  surface  of  the  lids  is  very  closely  connected,  and 
exceedingly  vascular.  It  is  continuous  with  the  general  gastro- 
pulmonary  mucous  membrane,  and  sympathizes  in  its  affections, 
as  may  be  observed  in  various  diseases.  From  the  surface  of  the 
eye  it  may  be  traced,  through  the  lachrymal  ducts,  into  the 
lachrymal  gland  ;  along  the  edges  of  the  lids  it  is  continuous 
with  the  mucous  lining  of  the  Meibomian  glands,  and,  at  the 
inner  angle  of  the  eye,  may  be  followed  through  the  lachrymal 
canals  into  the  lachrymal  sac,  and  thence  downwards,  through 
the  nasal  duct,  into  the  inferior  meatus  of  the  nose. 

The  caruncula  lachrymalis  is  the  small  reddish  body  which 
occupies  the  lacus  lachrymalis  at  the  inner  canthus  of  the  eye. 
In  health,  it  presents  a  bright  pink  tint ;  in  sickness,  it  loses  its 
color,  and  becomes  pale.  It  consists  of  an  assemblage  of  fol- 
licles similar  to  the  Meibomian  glands,  embedded  in  a  fibro-car- 
tilaginous  tissue,  and  is  the  source  of  the  whitish  secretion  which 
so  constantly  forms  at  the  inner  angle  of  the  eye.  It  is  covered 
with  minute  hairs,  which  are  sometimes  so  long  as  to  be  visible 
to  the  naked  eye. 

Immediately  to  the  outer  side  of  the  caruncula  is  a  slight  du- 
plicature  of  the  conjunctiva,  called  plica  semilunaris,  which 
contains  a  minute  plate  of  cartilage,  and  is  the  rudiment  of  the 
third  lid  of  animals,  the  membrana  nictitans  of  birds. 

Vessels  and  Nerves. — The  palpebrae  are  supplied  internally 
with  arteries  from  the  ophthalmic,  and  externally  from  the  facial 
and  transverse  facial.  Their  nerves  are  branches  of  the  fifth,  and 
of  the  facial. 


LACHRYMAL  APPARATUS.  261 

LACHRYMAL  APPARATUS. 

The  lachrymal  apparatus  consists  of  the  lachrymal  gland,  with 
its  excretory  ducts;  the  puncta  lachrymalia and  lachrymal  canals; 
the  lachrymal  sac  and  nasal  duct. 

The  lachrymal  gland  is  brought  into  view  by  detaching  the  broad 
tarsal  ligament  from  its  connection  with  the  upper  margin  of  the  orbit, 
and  removing  some  cellular  tissue  and  fat.  The  gland  has  been  already 
described  with  the  dissection  of  the  orbit  (p.  139).  At  the  present  time 
the  relations  of  the  palpebral  portion  may  be  more  accurately  observed, 
together  with  the  excretory  ducts. 

The  lachrymal  gland  consists  of  two  portions,  orbital  and 
palpebral.  The  orbital  portion,  the  larger  of  the  two,  is  flattened 
in  form,  and  lies  against  the  periosteum  of  the  orbit,  its  anterior 
border  being  in  relation  with  the  broad  tarsal  ligament.  The 
palpebral  portion  is  connected  with  the  anterior  border  of  the 
orbital  portion,  by  means  of  the  dense  fibrous  membrane,  which 
invests  both  portions.  It  is  oblong  in  shape,  lies  in  contact  with 
the  broad  tarsal  ligament,  and  is  in  relation,  by  its  lower  border, 
with  the  tarsal  cartilage  of  the  upper  lid.  The  excretory  ducts 
of  the  lachrymal  gland  are  eight  to  twelve  in  number.  They 
open  upon  the  conjunctiva,  in  the  direction  of  a  curved  line, 
situated  a  little  above  the  tarsal  cartilage  at  the  outer  part  of  the 
upper  lid. 

Lachrymal  Canals. — The  lachrymal  canals  commence  at  the 
minute  openings,  puncta  lachrymalia,  seen  upon  the  lachrymal 
papillae  of  the  lids  at  the  outer  extremity  of  the  lacus  lachryma- 
lis,  and  proceed  inwards  to  the  lachrymal  sac,  where  they  termi- 
nate beneath  a  valvular  semilunar  fold  of  the  lining  membrane 
of  the  sac.  The  superior  duct  at  first  ascends,  and  then  turns 
suddenly  inwards  towards  the  sac,  forming  an  abrupt  angle. 
The  inferior  duct  forms  the  same  kind  of  angle,  by  descending 
at  first,  and  then  turning  abruptly  inwards.  They  are  dense  and 
elastic  in  structure,  and  remain  constantly  open,  so  that  they  act 
like  capillary  tubes,  in  absorbing  the  tears  from  the  surface  of 
the  eye.  The  two  fasciculi  of  the  tensor  tarsi  muscle  are  inserted 
into  these  ducts,  and  serve  to  draw  them  inwards. 

The  lachrymal  sac  is  the  upper  extremity  of  the  nasal  duct, 
and  is  scarcely  moro  dilated  than  the  rest  of  the  canal.  It  is 
lodged  in  the  groove  of  the  lachrymal  bone,  and  is  often  dis- 
tinguished, internally,  from  the  nasal  duct,  by  a  semilunar  or  cir- 
cular valve.  The  sac  consists  of  mucous  membrane,  but  is 
covered  in,  and  retained  in  its  place  by  a  fibrous  expansion, 
derived  from  the  tendon  of  the  orbicularis,  which  is  inserted  into 
the  ridge  on  the  lachrymal  bone  ;  it  is  also  covered  by  the  tensor 
tarsi  muscle,  which  arises  from  the  same  ridge,  and  in  its  action 


262 


THE  DISSECTOR. 


upon  the  lachrymal  canals  may  serve  to  compress  the  lachrymal 
sac. 

The  nasal  duct  is  a  short  canal,  about  three-quarters  of  an  inch 
in  length,  directed  downwards,  backwards,  and  a  little  outwards 


Fig.  80. 


THE  LACHRYMAL  AP- 
PARATUS AND  TARSAL 
CARTILAGES  OF  THE  EYE- 
LIDS.— 1.  The  tarsal  car- 
tilage of  the  upper  lid.  2. 
The  tarsal  cartilage  of  the 
lower  lid ;  the  openings 
along  the  edges  of  the  lids 
are  those  of  the  Meibo- 
mian  ducts.  3.  The  ca- 
runcula  lachrymalis.  4. 
The  lachrymal  gland  pour- 
ing out  its  secretion  by 
seven  small  ducts.  5. 
The  lachrymal  tubercles, 
with  the  openings  of  the 
lachrymal  ducts,  called 
puncta  lachrymalia.  6,  6. 
The  lachrymal  ducts.  7. 
The  lachrymal  sac.  8. 
The  nasal  duct.  9.  Its 
termination  in  the  inferior 
naeatus  of  the  nose.  10. 
The  inferior  turbinated 
bone. 


to  the  inferior  meatus  of  the  nose,  where  it  terminates  by  an  ex- 
panded orifice.1  It  is  lined  by  mucous  membrane,  which  is  con- 
tinuous with  the  conjuctiva  above,  and  with-  the  pituitary  mem- 
brane of  the  nose  below.  Obstruction,  from  inflammation  and 
suppuration  of  this  duct,  constitutes  the  disease  called  fistula 
lachrymalis. 

Vessels  and  Nerves. — The  lachrymal  gland  is  supplied  with 
blood  by  the  lachrymal  branch  of  the  ophthalmic  artery  ;  and 
with  nerves,  by  the  lachrymal  branch  of  the  ophthalmic  nerve. 

THE   EYEBALL. 

The  form  of  the  eyeball  is  that  of  a  sphere,  of  about  one  inch 
in  diameter,  having  the  segment  of  a  smaller  sphere  engrafted 
upon  its  anterior  surface,  which  increases  its  antero-posterior 
diameter.  The  axes  of  the  two  eyeballs  are  parallel  with  each 
other,  but  do  not  correspond  with  the  axes  of  the  orbits,  which 
are  directed  outwards.  The  optic  nerves  follow  the  direction  of 
the  orbits,  and,  therefore,  enter  the  eyeballs  to  their  nasal  side. 


[This  orifice  is  more  slit-like  than  "expanded."] 


THE   EYEBALL.  263 

For  the  dissection  of  the  eyeball,  the  student  must  procure  some 
sheep's  eyes  from  the  butcher ;  the  eyes  in  his  own  subject  will  be  too 
far  advanced  in  decomposition  to  be  made  use  of  by  the  time  he  is  able 
to  give  his  attention  to  them.  Should  he  be  able  to  procure  a  fresh 
human  eye,  the  difficulty  will  be  removed ;  but  for  all  the  purposes  of 
dissection,  the  sheep's  or  bullock's  eye  is  preferable.  For  external  form, 
he  must  study  the  human  eye.  To  examine  the  exterior  of  the  eyeball, 
the  muscles,  fat,  and  cellular  tissue  which  invest  it  must  be  carefully 
dissected  away. 

The  globe  of  the  eye  is  composed  of  tunics,  and  of  refracting 
media  called  humors.  The  tunics  are  three  in  number,  the — 

1.  Sclerotic  and  cornea. 

2.  Choroid,  iris,  and  ciliary  processes, 

3.  Retina  and  zonula  ciliaris. 
The  humors  are  also  three — 

Aqueous,  Crystalline  (lens),  Yitreous. 

FIRST  TUNIC. — The  sclerotic  and  cornea  form  the  external 
tunic  of  the  eyeball,  and  give  it  its  peculiar  form.  Four-fifths  of 
the  globe  are  invested  by  the  sclerotic,  the  remaining  fifth  by  the 
cornea. 

The  sclerotic  (crx^poj,  hard)  is  a  dense  fibrous  membrane, 
thicker  behind  than  in  front.  It  is  continuous,  posteriorly,  with 
the  sheath  of  the  optic  nerve,  which  is  derived  from  the  dura 
mater,  and  is  pierced  by  that  nerve  as  well  as  by  the  ciliary  nerves 
and  arteries.  Anteriorly  it  presents  a  bevelled  edge,  which  re- 
ceives the  cornea  in  the  same  way  that  a  watch-glass  is  received 
by  the  groove  in  its  case.  Its  anterior  surface  is  covered  by  a 
thin  tendinous  layer,  the  tunica  albugitiea,  derived  from  the  ex- 
pansion of  the  tendons  of  the  four  recti  muscles.  By  its  posterior 
surface  it  gives  attachment  to  the  two  oblique  muscles.  The 
tunica  albuginea  is  covered,  for  a  part  of  its  extent,  by  the  mu- 
cous membrane  of  the  front  of  the  eye,  the  conjunctiva ;  and,  by 
reason  of  the  brilliancy  of  its  whiteness,  gives  occasion  to  the 
common  expression,  "  the  white  of  the  eye." 

At  the  entrance  of  the  optic  nerve,  the  sclerotic  forms  a  thin 
cribriform  lamella  (lamina  cribrosa),  which  is  pierced  by  a 
number  of  minute  openings  for  the  passage  of  the  nervous  fila- 
ments. One  of  these  openings,  larger  than  the  rest,  and  situated 
in  the  centre  of  the  lamella,  is  the  porus  opticus,  through  which 
the  arteria  centralis  retinae  enters  the  eyeball. 

The  cornea  (corneus,  horny)  is  the  transparent  projecting  layer 
that  constitutes  the  anterior  fifth  of  the  globe  of  the  eye.  In  its 
form  it  is  circular,  concavo-convex,  and  resembles  a  watch-glass. 
It  is  received  by  its  edge,  which  is  sharp  and  thin,  within  the 
bevelled  border  of  the  sclerotic,  to  which  it  is  very  firmly  attached, 
and  it  is  somewhat  thicker  than  the  anterior  portion  of  that 


264 


THE   DISSECTOR. 


tunic.  When  examined  from  the  exterior,  its  vertical  diameter 
is  seen  to  be  about  one-sixteenth  shorter  than  the  transverse,  in 
consequence  of  the  overlapping  above  and  below,  of  the  margin 


Fig.  81. 


THE  EXTERNAL  TUNIC 
OF  THE  EYE. — 1.  The 
sclerotic  coat.  2.  The 
tunica  albuginea,  formed 
by  the  expansion  of  the 
tendons  of  the  four  recti 
muscles.  3.  The  inser- 
tion of  the  superior  rectus. 
4.  The  insertion  of  the 
inferior  rectus.  5.  The 
insertion  of  the  external 
rectus.  6.  Small  open- 
ings in  the  sclerotic  for  the 
passage  of  the  ciliary  arte- 
ries and  nerves.  7.  The 
optic  nerve,  which  be- 
comes constricted  at  its 
point  of  entrance  into  the 
globe  of  the  eye.  8.  The 


of  the  sclerotica;  on  the  interior,  however,  its  outline  is  perfectly 
circular. 

The  cornea  is  composed  of  four  layers  :  namely,  of  the  conjunctiva,  of 
the  cornea  proper  (which  consists  of  several  thin  lamellae  connected 
together  by  an  extremely  fine  cellular  tissue),  of  the  cornea  elastica  (a 
"  fine,  elastic,  and  exquisitely  transparent  membrane,  exactly  applied  to 
the  inner  surface  of  the  cornea  proper"),  and  of  the  lining  membrane  of 
the  anterior  chamber  of  the  eyeball.  The  cornea  elastica  is  remarkable 
for  its  perfect  transparency  even  when  submitted  for  many  days  to  the 
action  of  water  or  alcohol,  while  the  cornea  proper  is  rendered  opaque  by 
the  same  immersion.  To  expose  this  membrane,  Dr.  Jacob  suggests  that 
the  eye  should  be  placed  in  water  for  six  or  eight  days,  and  then  that  all 
the  opaque  cornea  should  be  removed  layer  after  layer.  Another  cha- 
racter of  the  cornea  elastica  is  its  great  elasticity,  which  causes  it  to  roll 
up  when  divided  or  torn,  in  the  same  manner  as  the  capsule  of  the  lens. 
The  use  of  this  layer,  according  to  Dr.  Jacob,  is  "  to  preserve  the  requisite 
permanent  correct  curvature  of  the  flaccid  cornea  proper." 

The  opacity  of  the  cornea,  produced  by  pressure  on  the  globe,  results 
from  infiltration  of  fluid  into  the  cellular  tissue  connecting  its  layers. 
This  appearance  cannot  be  produced  in  a  sound  living  eye,  although  a 
small  quantity  of  serous  fluid  (liquor  cornese)  is  said  to  occupy  the  areolfe 
of  the  cellular  tissue. 

Dissection. — The  sclerotic  and  cornea  are  now  to  be  dissected  away 
from  the  second  tunic.  This,  with  care,  may  be  easily  performed,  the 
only  firm  connections  subsisting  between  them  being  at  the  circumfer- 
ence of  the  iris,  the  entrance  of  the  optic  nerve,  and  the  perforation  of  the 
ciliary  nerves  and  arteries.  Pinch  up  a  fold  of  the  sclerotic  near  its 
anterior  circumference,  and  make  a  small  opening  into  it ;  then  raise  the 
edge  of  the  tunic,  and,  with  a  pair  of  fine  scissors  having  a  probe  point, 
divide  the  entire  circumference  of  the  sclerotic,  and  cut  it  away  bit  by 


CHOROID   MEMBRANE.  265 

bit.  Then  separate  it  from  its  attachment  around  the  circumference  of 
the  iris  by  a  gentle  pressure  with  the  edge  of  the  knife.  The  dissection 
oi  tli.  eye  must  be  conducted  under  water. 

In  the  course  of  this  dissection  the  ciliary  nerves  and  long  ciliary  arte- 
?vYx  will  be  seen  passing  forwards  between  the  sclerotic  and  choroid,  to 
be  distributed  to  the  iris. 

SECOND  TUNIC. — The  second  tunic  of  the  eyeball  is  formed  by 
the  choroid,  ciliary  ligament,  and  iris,  the  ciliary  processes  being 
an  appendage  developed  from  its  inner  surface. 

The  choroid1  is  a  vascular  membrane  of  a  rich  chocolate-brown 
color  upon  its  external  surface,  and  of  a  deep  black  color  within. 
It  is  connected  to  the  sclerotic,  externally,  by  an  extremely  fine 
cellular  tissue  (membrana  fusca),  and  by  nerves  and  vessels. 
Internally  it  is  in  simple  contact  with  the  third  tunic  of  the  eye, 
the  retina.  It  is  pierced  posteriorly  for  the  passage  of  the  optic 
nerve,  and  is  connected  anteriorly  with  the  iris,  ciliary  processes, 
and  with  the  line  of  junction  of  the  cornea  and  sclerotic,  by  a 
dense  white  structure,  the  ciliary  ligament,  which  surrounds  the 
circumference  of  the  iris  like  a  ring. 

Fig.  82. 

THE  SECOND  TUNIC  OF 
THE  EYE. — 1.  The  choroid 
membrane  upon  which 
arc  seen  the  curved  lines 
marking  the  arrangement 
of  the  venae  vorticosse. 
2,  2.  Ciliary  nerves.  3. 
A  long  ciliary  artery  and 
nerve.  4.  The  ciliary  li- 
gament. 5.  The  iris:  the 
two  sets  of  fibres  are  very 
distinctly  seen,  the  exter- 
nal, radiating  towards  the 
centre,  and  the  internal, 
circular,  surrounding  the 
pupil  (6). 

The  choroid  membrane  is  composed  of  three  layers,  an  external  or 
venous  layer,  which  consists  principally  of  veins  arranged  in  a  peculiar 
manner :  hence  they  have  been  named  vence  vorticosce.  The  marking  on 


1  The  word  choroid  has  been  very  much  abused  in  anatomical  lan- 
guage. It  was  originally  applied  to  the  membrane  of  the  foetus  called 
chorion,  from  the  Greek  word  xf+iw  (domicilium),  that  membrane  being, 
as  it  were,  the  abode  or  receptacle  of  the  foetus.  Xo>ov  comes  from  x.uptot, 
to  take  or  receive.  Now  it  so  happens  that  the  chorion  in  the  ovum  is  a 
vascular  membrane  of  peculiar  structure.  Hence  the  term  choroid 
(%&?tn — iftof,  like  the  chorion)  has  been  used  indiscriminately  to  signify 
vascular  structures,  (as  in  the  choroid  membrane  of  the  eye,  the  choroid 
plexus,  &c.)  ;  and  we  find  Cruveilhier  (in  his  work  on  Anatomy,  vol.  iii. 
p.  463)  saying,  in  a  note,  "Choroide  eat  synonyme  de  vasculeuse." 
23 


266  THE   DISSECTOR. 

the  surface  of  the  membrane  produced  by  these  veins  resembles  so  many 
centres  to  which  a  number  of  curved  lines  converge.  It  is  this  layer 
which  is  connected  with  the  ciliary  ligament.  The  middle  or  arterial- 
layer  (tunica  Ruyschiana),  is  formed  principally  by  the  ramifications  of 
minute  arteries.  It  is  reflected  inwards  at  its  junction  with  the  ciliary 
ligament,  so  as  to  form  the  ciliary  processes.  The  internal  layer  is  a  de- 
licate membrane  (membrana  pigmenti),  composed  of  several  laminse  of 
nucleated  hexagonal  cells,  which  contain  the  granules  of  pigmenturn, 
and  are  arranged  so  as  to  resemble  a  tessellated  pavement. 

In  animals,  the  pigmentum  nigrum,  on  the  posterior  wall  of  the  eye- 
ball, is  replaced  by  a  layer  of  considerable  extent  and  of  metallic  bril- 
liancy, called  the  tapetum. 

The  ciliary  ligament,  or  circle  (annulus  albidus),  is  the  bond 
of  union  between  the  external  and  middle  tunics  of  the  eyeball, 
and  serves  to  connect  the  cornea  and  sclerotic,  at  their  line  of 
junction,  with  the  iris  and  external  layer  of  the  choroid.  It  is 
also  the  point  to  which  the  ciliary  nerves  and  vessels  proceed 
previously  to  their  distribution,  and  it  receives  the  anterior 
ciliary  arteries  through  the  anterior  margin  of  the  sclerotic.  A 
minute  vascular  canal  is  situated  within  the  ciliary  ligament, 
called  the  ciliary  canal,  or  the  canal  of  Fontana,  from  its  dis- 
coverer. 

The  iris  (iris,  a  rainbow),  is  so  named  from  its  variety  of  color 
in  different  individuals :  it  forms  a  septum  between  the  anterior 
and  posterior  chambers  of  the  eye,  and  is  pierced  somewhat  to 
the  nasal  side  of  its  centre  by  a  circular  opening,  which  is  called 
the  pupil.  By  its  periphery  it  is  connected  with  the  ciliary  liga- 
ment, and  by  its  inner  circumference  forms  the  margin  of  the 
pupil ;  its  anterior  surface  looks  towards  the  cornea,  and  the  pos- 
terior towards  the  ciliary  processes  and  lens. 

The  iris  is  composed  of  two  layers,  anterior  or  muscular,  consisting  of 
radiating  fibres,  which  converge  from  the  circumference  towards  the 
centre,  and  have  the  power  of  dilating  the  pupil,  and  circular,  which 
surround  the  pupil  like  a  sphincter,  and  by  their  action  produce  con- 
traction of  its  area.  The  posterior  layer  is  of  a  deep  purple  tint,  and  is 
thence  named  uvea,  from  its  resemblance  in  color  to  a  ripe  grape. 

The  -ciliary  processes  (corpus  ciliare),  may  be  seen  in  two  ways, 
either  by  removing  the  iris  from  its  attachment  to  the  ciliary 
ligament,  when  a  front  view  of  the  processes  will  be  obtained, 
or  by  making  a  transverse  section  through  the  globe  of  the  eye, 
when  they  may  be  examined  from  behind.  They  consist  of  a 
number  of  triangular  folds,  formed  apparently  by  the  plaiting  of 
the  middle  and  internal  layer  of  the  choroid.  According  to 
Zinn,  they  are  about  sixty  in  number,  and  may  be  divided  into 
large  and  small,  the  latter  being  situated  in  the  spaces  between 
the  former.  Their  periphery  is  connected  with  the  ciliary  liga- 
ment, and  is  continuous  with  the  middle  and  internal  layer  of  the 
choroid.  The  central  border  is  free,  and  rests  against  the  cir- 


THE   RETINA.  26t 

cumference  of  the  lens.  The  anterior  surface  corresponds  with 
the  uvea;  the  posterior  receives  the  folds  of  the  zonula  ciliaris 
between  its  processes,  and  thus  establishes  a  connection  between 
the  choroid  and  the  third  tunic  of  the  eye.  The  ciliary  pro- 
cesses are  covered  with  a  thick  layer  of  pigmentum  nigrum, 
which  is  more  abundant  upon  them,  and  upon  the  anterior  part 
of  the  choroid,  than  upon  the  posterior  part  of  the  latter. 
When  the  pigment  is  washed  off,  the  processes  are  of  a  whitish 
color. 

THIRD  TUNIC. — The  third  tunic  of  the  eye  is  the  retina,  which 
is  prolonged  forwards  to  the  lens  by  the  zonula  ciliaris. 

I>i. section. — If,  after  the  preceding  dissection,  the  choroid  membrane 
be  carefully  raised  and  removed,  the  eye  being  kept  under  water,  the 
retina  may  be  seen  very  distinctly. 

The  retina  is  composed  of  three  layers : — 

External,  or  Jacob's  membrane, 
Middle,          Nervous  membrane, 
Internal,        Vascular  membrane. 

Jacobs  membrane  is  extremely  thin,  and  is  seen  as  a  mere  film 
when  the  freshly  dissected  eye  is  suspended  in  water.  Examined 
by  the  microscope,  it  is  found  to  be  composed  of  cells  having  a 
tessellated  arrangement.  Dr.  Jacob  considers  it  to  be  a  serous 
membrane. 

The  nervous  membrane  is  the  expansion  of  the  optic  nerve, 
and  forms  a  thin  semi-transparent  bluish-white  layer,  which  en- 
velopes the  vitreous  humor,  and  extends  forward  to  the  com- 
mencement of  the  ciliary 

processes,  where  it  ter-  Fig.  83. 

minates  by  an  abrupt 
scalloped  margin.  Ac- 
cording to  Treviranus, 
this  layer  is  composed 
of  cylindrical  fibres, 
which  proceed  from  the 
optic  nerve,  and,  near 
their  termination,  bend 
abruptly  inwards,  to 
form  the  internal  papil- 
lary layer,  which  lies  in 
contact  with  the  hyaloid 
membrane  :  each  fibre  THE  THIRD  TtJNIC  OF  THE  EYE.— 1.  The  re- 

*•*    4r-        u     •*  tina  terminating  anteriorly  in  a  scalloped  border. 

Constituting  by  Its  extre-  2.  The  foramen  of  Soemmering.  3.  The  zonula 
mity  a  distinct  papilla.  ciliaris.  4.  The  lens. 

The    vascular    mem- 
brane consists  of  the  ramifications  of  a  minute  artery,  the  arteria 


268  THE   DISSECTOR. 

centralis  retinae,  and  its  accompanying  vein  :  the  artery  pierces 
the  optic  nerve,  and  enters  the  globe  of  the  eye  through  the 
poms  opticus,  in  the  centre  of  the  lamina  cribrosa.  This  artery 
may  be  seen  very  distinctly  by  making  a  transverse  section  of  the 
eyeball.  Its  branches  are  continued  anteriorly  into  the  zonula 
ciliaris.  The  vascular  layer  forms  distinct  sheaths  for  the  nervous 
papilla?,  which  constitute  the  inner  surface  of  the  retina. 

In  the  centre  of  the  posterior  part  of  the  globe  of  the  eye  the 
retina  presents  a  circular  spot,  which  is  called  the  foramen  of 
Soemmering  ;  it  is  surrounded  by  a  yellow  halo,  the  limbm  luteus, 
and  is  frequently  obscured  by  an  elliptical  fold  of  the  retina,  which 
has  been  regarded  as  a  normal  condition  of  the  membrane.  The 
term  foramen  is  misapplied  to  this  spot,  for  the  vascular  layer 
and  the  membrana  Jacobi  are  continued  across  it ;  the  nervous 
substance  alone  appearing  to  be  deficient.  It  exists  only  in  ani- 
mals having  the  axes  of  the  eyeballs  parallel  with  each  other,  as 
man,  quadrumana,  and  some  saurian  reptiles,  and  is  said  to  give 
passage  to  a  small  lymphatic  vessel. 

The  zonula  ciliaris  (zonula  of  Zinn)  is  a  thin  vascular  layer, 
which  connects  the  anterior  margin  of  the  retina  with  the  ante- 
rior surface  of  the  lens  near  its  circumference.  It  presents  upon 
its  surface  a  number  of  small  folds  corresponding  with  the  ciliary 
processes,  between  which  they  are  received.  These  processes  are 
arranged  in  the  form  of  rays  around  the  lens,  and  the  spaces 
between  them  are  stained  by  the  pigmentum  nigrum  of  the  ciliary 
processes.  They  derive  their  vessels  from  the  vascular  layer  of 
the  retina.  The  under  surface  of  the  zonula  is  in  contact  with 
the  hyaloid  membrane,  and  around  the  lens  forms  the  anterior 
fluted  wall  of  the  canal  of  Petit. 

The  connection  between  these  folds  and  the  ciliary  processes  may  be 
demonstrated  by  dividing  an  eye  transversely  into  two  portions,  then 
raising  the  anterior  half  and  allowing  the  vitreous  humor  to  fall  out  by 
its  own  weight.  The  folds  of  the  zonula  will  then  be  seen  to  be  drawn 
out  from  between  the  folds  of  the  ciliary  processes. 

HUMORS. — The  aqueous  humor  is  situated  in  the  anterior  and 
posterior  chambers  of  the  eye ;  it  is  a  weakly  albuminous  fluid, 
with  an  alkaline  reaction,  and  a  specific  gravity  very  little  greater 
than  that  of  distilled  water.  According  to  Petit,  it  scarcely 
exceeds  four  or  five  grains  in  weight. 

The  anterior  chamber  is  the  space  intervening  between  the  cor- 
nea in  front,  and  the  iris  and  pupil  behind.  The  posterior 
chamber  is  the  narrow  space,  less  than  half  a  line  in  depth,1 
bounded  by  the  posterior  surface  of  the  iris  and  pupil  in  front, 

1  Winslow  and  Lieutaud  thought  the  iris  to  be  in  contact  with  the 
lens.  It  frequently  adheres  to  the  capsule  of  the  latter  in  iritis.  The 
depth  of  the  posterior  chamber  is  greater  in  old  than  in  young  persons. 


HUMORS   OP   THE   EYE. 


269 


and  by  the  ciliary  processes,  zonula  ciliaris,  and  lens  behind.  The 
two  chambers  are  lined  by  a  thin  layer,  the  secreting  membrane 
of  the  aqueous  humor. 

The  vitreous  humor  forms  the  principal  bulk  of  the  globe  of 
the  eye.  It  is  an  albuminous  and  highly  transparent  fluid,  in- 

Fig.  84. 

A  LONGITUDINAL  SEC- 
TION OF  THE  GLOBE  OF  THE 
EVE. —  1.  The  sclerotic, 
thicker  behind  than  the 
front.  2.  The  lamina  cri- 
brosa ;  the  thin  layer  of 
the  sclerotic,  which  is 
pierced  with  holes  for  the 
]i:i.^:i#e  of  the  nervous  sub- 
stance of  the  optic  nerve. 

3.  The    cornea,    which   is  

seen  to  be  inserted  into  the 

border  of  the  sclerotic  coat 

4.  The  choroid  membrane 
(the  dark  layer).     5.   The 
ciliary   ligament.      6.    The 
iris.     *  The  pupil.     7.  The 
ciliary  processes.      8.   The 

retina  (the  white  layer).  9.  The  dotted  line  represents  the  zonula  ciliaris, 
which  is  continued  from  the  anterior  border  of  the  retina  of  the  capsule  of  the 
lens.  10.  The  innermost  line  is  the  hyaloid  membrane,  which  may  be  followed 
behind  the  lens.  11.  The  canal  of  Petit.  12.  The  anterior  chamber  of  the 
eye.  The  narrow  space  between  the  iris  and  the  ciliary  processes  and  lens  is 
the  posterior  chamber.  13.  The  lens  inclosed  in  its  capsule.  14.  The  posterior 
cavity  of  the  globe,  in  which  the  vitreous  humor  is  lodged.  15.  A  minute  ar- 
tery, a  branch  of  the  anterior  centralis  retinae,  which  traverses  the  centre  of  the 
vitreous  humor  to  reach  the  capsule  of  the  lens. 

closed  in  a  delicate  membrane,  the  hyaloid.  From  the  inner 
surface  of  this  membrane,  numerous  thin  lamellae  are  directed 
inwards,  and  form  compartments  in  which  the  fluid  is  contained. 
According  to  Hanover,  these  lamellae  have  a  radiated  arrange- 
ment, like  those  on  the  transverse  section  of  an  orange,  and  are 
about  180  in  number.  In  the  centre  of  the  vitreous  humor  is  a 
tubular  canal,  through  which  a  minute  artery  is  conducted  from 
the  arteria  centralis  retinai  to  the  capsule  of  the  lens.  This  ves- 
sel is  injected  without  difficulty  in  the  foetus. 

The  crystalline  humor  or  lens  is  situated  immediately  behind 
the  pupil,  and  is  surrounded  by  the  ciliary  processes,  which 
tiirhtly  overlap  its  margin.  It  is  more  convex  on  the  posterior 
than  on  the  anterior  surface,  and  is  imbedded  in  the  anterior  part 
of  the  vitreous  humor,  from  which  it  is  separated  by  the  hyaloid 
membrane.  It  is  invested  by  a  peculiarly  transparent  and  elastic 
membrane,  the  capsule  of  the  lens,  which  contains  a  small  quan- 
tity of  fluid,  called  liquor  Morgayni,  and  is  retained  in  its  place 

23* 


270  THE  DISSECTOR. 

by  the  attachment  of  the  zonula  ciliaris.  Dr.  Jacob  is  of  opinion 
that  the  lens  is  connected  to  its  capsule  by  means  of  cellular 
tissue,  and  that  the  liquor  Morgagni  is  the  result  of  a  cadaveric 
change. 

The  lens  consists  of  concentric  layers,  of  which  the  external  are  soft, 
the  next  firmer,  and  the  central  form  a  hardened  nucleus.  These  layers 
are  best  demonstrated  by  boiling,  or  by  immersion  in  alcohol,  when  they 
separate  easily  from  each  other.  Another  division  of  the  lens  takes 
place  at  the  same  time  :  it  splits  into  three  triangular  segments,  which 
have  the  sharp  edge  directed  towards  the  centre,  and  the  base  towards 
the  circumference.  The  concentric  lamellae  are  composed  of  minute 
parallel  fibres,  which  are  united  with  each  other  by  means  of  scalloped 
borders,  the  convexity  on  the  one  border  fitting  into  the  concave  scallop 
upon  the  other. 

Immediately  around  the  circumference  of  the  lens  is  a  triangu- 
lar canal,  the  canal  of  Petit,  about  a  line  and  a  half  in  breadth. 
It  is  bounded,  in  front  by  the  flutings  of  zonula  ciliaris  ;  behind, 
by  the  hyaloid  membrane ;  and  within,  by  the  border  of  the 
lens. 

The  VESSELS  of  the  globe  of  the  eye  are  the  long  and  short, 
and  anterior  ciliary  arteries,  and  the  arteria  centralis  retinae. 
The  long  ciliary  arteries,  two  in  number,  pierce  the  posterior 
part  of  the  sclerotic,  and  pass  forward  on  each  side,  between 
that  membrane  and  the  choroid,  to  the  ciliary  ligament,  where 
they  divide  into  two  branches,  which  are  distributed  to  the  iris. 
The  short  ciliary  arteries  pierce  the  posterior  part  of  the  sclerotic 
coat,  and  are  distributed  to  the  middle  layer  of  the  choroid 
membrane.  The  anterior  ciliary  are  branches  of  the  muscular 
arteries.  They  enter  the  eye  through  the  anterior  part  of  the 
sclerotic,  and  are  distributed  to  the  iris.  It  is  the  increased 
number  of  these  latter  arteries,  in  iritis,  that  gives  rise  to  the 
peculiar  red  zone  around  the  circumference  of  the  cornea. 

The  arteria  centralis  retina  enters  the  optic  nerve  at  about 
half  an  inch  from  the  globe  of  the  eye,  and,  passing  through  the 
porns  opticus,  is  distributed  upon  the  inner  surface  of  the  retina, 
forming  its  vascular  layer;  one  branch  pierces  the  centre  of  the 
vitreous  humor  and  supplies  the  capsule  of  the  lens. 

The  nerves  of  the  eyeball  are  the  optic,  two  ciliary  nerves  from 
the  nasal  branch  of  the  ophthalmic,  and  the  ciliary  nerves  from 
the  ophthalmic  ganglion. 

Observations. — The  sclerotic  is  a  tunic  of  protection,  and  the 
cornea  a  medium  for  the  transmission  of  light.  The  choroid 
supports  the  vessels  destined  for  the  nutrition  of  the  eye,  and  by 
its  pigmentum  nigrum  absorbs  all  loose  and  scattered  rays  that 
might  confuse  the  image  impressed  upon  the  retina.  The  iris, 
by  means  of  its  powers  of  expansion  and  contraction,  regulates 
the  quantity  of  light  admitted  through  the  pupil.  If  the  iris  be 


THE   ORGAN   OF    HEARING. 


271 


thin,  and  the  rays  of  light  pass  through  its  substance,  they  are 
immediately  absorbed  by  the  uvea;  and  if  that  layer  be  insuffi- 
cient, they  are  taken  up  by  the  black  pigment  of  the  ciliary 
processes.  In  Albinoes,  where  there  is  an  absence  of  pigmentuin 
nigrum,  the  rays  of  light  traverse  the  iris,  and  even  the  sclerotic, 
and  so  overwhelm  the  eye  with  light,  that  sight  is  destroyed, 
except  in  the  dimness  of  evening,  or  at  night.  In  the  manu- 
facture of  optical  instruments,  care  is  taken  to  color  their  inte- 
rior black,  with  the  same  object,  the  absorption  of  scattered  rays. 
The  transparent  lamellated  cornea  and  the  humors  of  the  eye 
have  for  their  office  the  refraction  of  the  rays  in  such  proportion 
as  to  direct  the  image  in  the  most  favorable  manner  upon  the 
retina.  Where  the  refracting  medium  is  too  great,  as  in  over 
convexity  of  the  cornea  and  lens,  the  image  falls  short  of  the 
retina  (myopia,  near-sightedness);  and  where  it  is  too  little,  the 
image  is  thrown  beyond  the  nervous  membrane  (presbyopia,  far- 
sightedness). These  conditions  are  rectified  by  the  use  of 
spectacles,  which  provide  a  differently  refracting  medium  ex- 
ternally to  the  eye,  and  thereby  correct  the  transmission  of 
light. 

THE  ORGAN  OP  HEARING. 

The  apparatus  of  hearing  is  composed  of  three  parts,  the  ex- 
ternal ear,  middle  ear  or  tympa- 


num, and  internal  ear  or  labyrinth. 

The  EXTERNAL  EAR  consists  of 
two  portions,  the  pinna  and  mea- 
tits  ;  the  former  representing  a 
kind  of  funnel  which  collects  the 
vibrations  of  the  atmosphere,  pro- 
ducing sounds,  and  the  latter  a 
tube  which  conveys  the  vibrations 
to  the  tympanum. 

The  PINNA  presents  a  number 
of  folds  and  hollows  upon  its 
surface,  which  have  different 
nuuies  assigned  to  them.  Thus, 
tlio  external  folded  margin  is 
called  the  helix  (?*e|,  a  fold).  The 
elevation  parallel  to  and  in  front 
of  the  helix  is  called  antihelix 
i,  opposite).  The  pointed 


Fig.  85. 


A  VIEW  OF  THE  LEFT  EAR  IN  ITS  NATURAL  STATE.  —  1,  2.  The  origin  and 
termination  of  the  helix.  3.  The  antihelix.  4.  The  antitragus.  5.  The  tra- 
gus.  6.  The  lobus  of  the  external  ear.  7.  Points  to  the  scapha,  and  is  on 
the  front  and  top  of  the  pinna.  8.  The  concha.  9.  The  meatus  auditorius  ex- 

tern us. 


2T2  THE   DISSECTOR. 

process,  projecting  like  a  valve  over  the  opening  of  the  ear  from 
the  face,  is  called  the  tragus  (rpayoj,  a  goat),  probably  from 
being  sometimes  covered  with  bristly  hair  like  that  of  a  goat ; 
and  a  tubercle  opposite  to  this  is  the  antitragus.  The  lower  de- 
pendent and  fleshy  portion  of  the  pinna  is  the  lobulus.  The  space 
between  the  helix  and  antihelix  is  named  the  fossa  innominata 
(scaphoidea).  Another  depression  is  observed  at  the  upper  ex- 
tremity of  the  antihelix,  which  bifurcates  and  leaves  a  triangular 
space  between  its  branches,  called  the  fossa  triangularis  (ovalis)  ; 
and  the  large  central  space,  to  which  all  the  channels  converge, 
is  the  concha,  which  opens  directly  into  the  meatus. 

The  pinna  is  composed  of  integument,  fibro- cartilage,  ligaments, 
and  muscles. 

The  integument  is  thin,  contains  an  abundance  of  sebaceous 
glands,  and  is  closely  connected  with  the  fibro- cartilage. 

The  integument  should  be  dissected  off  from  the  fibro-cartilage,  a  task 
of  some  difficulty,  in  consequence  of  the  close  adhesion  which  subsists 
between  them,  in  order  to  bring  into  view  the  cartilage  with  its  ligaments 
and  muscles.  Over  the  muscles  the  integument  must  be  raised  with 
care,  as,  from  their  paleness,  they  might  otherwise  be  dissected  away. 

The  fibro-cartilage  gives  form  to  the  pinna,  and  is  folded  so  as 
to  produce  the  various  convexities  and  grooves  which  have  been 
described  upon  its  surface.  The  helix  commences  in  the  concha, 
and  partially  divides  that  cavity  into  two  parts ;  on  its  anterior 
border,  where  it  commences  its  curve  upwards,  is  a  tubercle  or 
spine,  and  a  little  above  this  a  small  vertical  fissure,  the  fissure  of 
the  helix.  The  termination  of  the  helix  and  antihelix  forms  a 
lengthened  process,  the  processus  caudatus,  which  is  separated 
from  the  concha  by  an  extensive  fissure.  Upon  the  anterior  sur- 
face of  the  tragus  is  another  fissure,  thejissure  of  the  tragus,  and, 
in  the  lobulus,  the  fibro-cartilage  is  wholly  deficient.  The  fibro- 
cartilage  of  the  meatus  is  divided  from  the  concha  by  several  fis- 
sures (fissures  of  Santorinus),  and  at  the  upper  arid  anterior  part 
of  the  cylinder  there  is  a  considerable  space,  which  is  closed  by 
ligamentous  fibres ;  it  is  firmly  attached  at  its  termination  to  the 
processus  auditorius.  ;  .  - 

The  ligaments  of  the  external  ear  are  those  which  attach  the 
pinna  to  the  side  of  the  head,  viz :  the  anterior,  posterior,  and 
ligament  of  the  tragus  ;  and  those  of  the  fibro-cartilage,  which 
serve  to  preserve  its  folds  and  connect  the  opposite  margins  of 
the  fissures.  The  latter  are  two  in  number,  the  ligament  between 
the  concha  and  the  processus  caudatus,  and  the  broad  ligament 
which  extends  from  the  upper  margin  of  the  fibro-cartilage  of 
the  tragus  to  the  helix,  and  completes  the  meatus. 


TYMPANUM.  273 

The  proper  muscles  of  the  pinna  are  the — 

Major  helicis,  Antitragicus, 

Minor  helicis,  Transversus  auriculae, 

Tragicus,  Obliquus  auris. 

The  major  helicis  is  a  narrow  band  of  muscular  fibres  situated 
upon  the  anterior  border  of  the  helix.  It  arises  from  the  spine 
of  the  helix,  and  is  inserted  into  the  anterior  border  of  that  fold. 

The  minor  helicis  is  placed  upon  the  anterior  extremity  (crus) 
of  the  helix,  at  its  commencement  in  the  fossa  of  the  concha. 

The  tragicus  is  a  thin  quadrilateral  layer  of  muscular  fibres, 
situated  upon  the  tragus. 

The  antitragicus  arises  from  the  antitragus,  and  is  inserted 
into  the  posterior  surface  of  the  processus  caudatus  of  the  helix. 

The  transversus  auriculae,  partly  tendinous  and  partly  muscu- 
lar, extends  transversely  from  the  convexity  of  the  concha  to  that 
of  the  helix,  on  the  posterior  surface  of  the  pinna. 

The  obliquus  auris  (Tod)  is  a  small  band  of  fibres  passing  be- 
tween the  upper  part  of  the  convexity  of  the  concha  and  the  con- 
vexity immediately  above  it. 

Mr.  Tod1  describes,  besides,  a  contractor  meatiis,  or  trago- 
helicus  muscle. 

The  MEATUS  AUDITORIUS  is  a  canal,  partly  cartilaginous  and 
partly  osseous,  about  an  inch  in  length,  which  extends  inwards 
and  a  little  forwards  from  the  concha  to  the  tympanum.  It  is 
narrower  in  the  middle  than  at  each  extremity,  forms  an  oval 
cylinder,  the  long  diameter  being  vertical,  and  is  slightly  curved 
upon  itself,  the  concavity  looking  downwards. 

It  is  lined  by  an  extremely  thin  pouch  of  epithelium,  which, 
when  withdrawn  after  maceration,  preserves  the  form  of  the 
meatus.  Some  stiff  short  hairs  are  also  found  in  its  interior, 
which  stretch  across  the  tube,  and  prevent  the  ingress  of  insects 
and  dust.  In  the  substance  of  its  lining  membrane  are  a  number 
of  ceruminous  glands,  which  secrete  the  wax  of  the  ear. 

Vessels  and  Nerves. — The  pinna  is  plentifully  supplied  with 
arteries — by  the  anterior  auricular  from  the  temporal ;  by  the 
posterior  auricular  from  the  external  carotid  ;  and  by  a  branch 
from  the  occipital  artery. 

Its  nerves  are  derived  from  the  auriculo-temporal  of  the  fifth, 
the  posterior  auricular  of  the  facial,  and  the  auricularis  magnus 
of  the  cervical  plexus. 

MIDDLE  EAR  OR  TYMPANUM. 

The  tympanum  is  an  irregular  bony  cavity,  compressed  from 
without  inwards,  and  situated  within  the  petrous  bone.  It  is 

1  "  The  Anatomy  and  Physiology  of  the  Organ  of  Hearing,"  by  David 
Tod.  1832. 


2T4  THE   DISSECTOR. 

bounded,  externally,  by  the  meatus  and  membrana  tympani ;  inter- 
nally, by  the  base  of  the  petrous  bone ;  behind,  by  the  mastoid 

cells  ;  and,  throughout  the 

FiS-  86-  rest  of  its  circumference, 

by  the  thin  osseous  layer 
which  connects  the  petrous 
with  the  squamous  portion 
of  the  temporal  bone. 

The  membrana  tympani 
is  a  thin  and  semi-trans- 
parent membrane  of  an 
oval  shape,  its  long  diame- 
ter being  vertical.  It  is 
MEMBRANA  TYMPANI  FROM  THE  OUTER  (A)  in«?prtpH  into  n  o-rnnvA  cif 

AND  FROM  THE  INNER  (B)  SlDBB.-l.  Mem-   ]         *  mtO  a  grOOVC  Slt- 

brana  tympani.     2.  Malleus.     3.  Stapes.     4.     uated  around  the    Circum- 

incus.  ference    of    the    meatus, 

near  its  termination,  and 

is  placed  obliquely  across  the  area  of  that  tube,  the  direction  of  the 
obliquity  being  downwards  and  inwards.  It  is  concave  towards 
the  meatus,  convex  towards  the  tympanum,  and  composed  of 
three  layers,  external,  or  epithelial ;  middle,  fibrous  and  muscu- 
lar ;  and  internal,  mucous,  derived  from  the  mucous  lining  of  the 
tympanum. 

The  tympanum  contains  three  small  bones,  ossicula  auditus, 
viz  :  the  malleus,  incus,  and  stapes. 

The  malleus  (hammer)  consists  of  a  head,  neck,  handle  (manu- 
brium),  and  two  processes,  long  (processus  gracilis)  and  short 
(processus  brevis).  The  manubrium  is  connected  with  the  mem- 
brana tympani  by  its  whole  length,  extending  below  the  central 
point  of  that  membrane.  It  lies  beneath  the  mucous  layer  of  the 
membrane,  and  serves  as  a  point  of  attachment  to  which  the 
radiating  fibres  of  the  fibrous  layer  converge.  The  long  process 
descends  to  a  groove  near  the  fissura  Glaseri,  and  gives  attach- 
ment to  the  laxator  tympani  muscle.  Into  the  short  process  is 
inserted  the  tendon  of  the  tensor  tympani,  and  the  head  of  the 
bone  articulates  with  the  incus. 

The  incus  (anvil)  is  named  from  an  imagined  resemblance  to 
an  anvil.  It  has  also  been  likened  to  a  bicuspid  tooth,  having 
one  root  longer  than,  and  widely  separated  from,  the  other.  It 
consists  of  two  processes,  which  unite  nearly  at  right  angles,  and 
at  their  junction  form  a  flattened  body,  which  articulates  with  the 
head  of  the  malleus.  The  short  process  is  attached  to  the  mar- 
gin of  the  opening  of  the  mastoid  cells  by  means  of  a  ligament ; 
the  long  process  descends  nearly  parallel  with  the  handle  of  the 
malleus,  and  curves  inwards,  near  its  termination.  At  its  extre- 
mity is  a  small  globular  projection,  the  os  orbiculare,  which  in 


TYMPANUM.  275 

the  foetus  is  a  distinct  bone,  but  becomes  anchylosed  to  the  long 
process  of  the  incus  in  the  adult :  this  process  articulates  with 
the  head  of  the  stapes. 

The  stapes  is  shaped  like  a  stirrup,  to  which  it  bears  a  close 
resemblance.  Its  head  articulates  with  the  os  orbiculare,  and  the 
two  branches  (crura)  are  connected  by  their  extremities  with  a 
flat,  oval-shaped  plate,  representing  the  foot  of  the  stirrup.  The 
foot  of  the  stirrup  is  received  into  the  fenestra  ovalis,  to  the  mar- 
gin of  which  it  is  connected  by  means  of  a  ligament :  it  is  in  con- 
tact, by  its  surface,  with  the  membrana  vestibuli,  and  is  covered 
in  by  the  mucous  lining  of  the  tympanum.  The  neck  of  the  stapes 
gives  attachment  to  the  stapedius  muscle. 

The  ossicula  auditiis  are  retained  in  their  position  and  moved 
upon  themselves  by  means  of  ligaments  and  muscles. 

The  ligaments  are  three  in  number,  the  suspensory  ligament  of 
the  malleus,  which  is  attached  by  one  extremity  to  the  upper  wall 
of  the  tympanum,  and  by  the  other  to  the  head  of  the  malleus ; 
the  posterior  ligament  of  the  incus,  a  short  and  thick  band  which 
serves  to  attach  the  extremity  of  the  short  process  of  that  bone 
to  the  margin  of  the  opening  of  the  mastoid  cells ;  and  the  an- 
nular ligament  which  connects  the  margin  of  the  foot  of  the  stapes 
with  the  circumference  of  the  fenestra  ovalis.  These  ligaments 
have  been  described  as  muscles,  by  Mr.  Tod,  under  the  names  of 
superior  capitis  mallei,  obliquus  incudis  externus  posterior,  and 
musculus  vel  structura  stapedii  inferior.  Arnold  adds  as  a  fourth 
a  suspensory  ligament  of  the  incus. 

The  muscles  of  the  tympanum  are  four  in  number,  the — 
Tensor  tympani, 
Laxator  tympani, 
Laxator  tympani  minor, 
Stapedius. 

The  tensor  tympani  (musculus  internus  mallei)  arises  from  the 
spinous  process  of  the  sphenoid,  from  the  petrous  portion  of  the 
temporal  bone,  and  from  the  Eustachian  tube,  and  passes  forwards 
in  a  distinct  canal,  separated  from  the  tube  by  the  processus 
cochleariformis,  to  be  inserted  into  the  handle  of  the  malleus,  im- 
mediately below  the  root  of  the  processus  gracilis. 

The  laxator  tympani  (musculus  externus  mallei)  arises  from 
the  spinous  process  of  the  sphenoid  bone,  and  passes  through  an 
opening  in  the  fissura  Glaseri,  to  be  inserted  into  the  neck  of  the 
malleus,  just  above  the  root  of  the  processus  gracilis.  This  is 
regarded  as  a  ligament  (anterior  ligament  of  the  malleus)  by 
some  anatomists. 

The  laxator  tympani  minor  (posterior  ligament  of  the  malleus) 
arises  from  the  upper  margin  of  the  meatus,  and  is  inserted  into 


276 


THE   DISSECTOR. 


the  handle  of  the  malleus,  and  the  processus  brevis.  This  is  re- 
garded as  a  ligament  by  some  anatomists. 

The  stapedius  arises  from  the  interior  of  the  pyramid,  and 
escapes  from  its  summit  to  be  inserted  into  the  neck  of  the  stapes. 

Foramina. — The  openings  in  the  tympanum  are  ten  in  number, 
Jive  large,  frudjive  small;  they  are — 


Large  Openings. 
Meatus  auditorius, 
Fenestra  ovalis, 
Fenestra  rotunda, 
Mastoid  cells, 
Eustachian  tube. 


Small  Openings. 
Entrance  of  chorda  tympani, 
Exit  of  the  chorda  tympani, 
For  the  laxator  tympani, 
For  the  tensor  tympani, 
For  the  stapedius. 
The  opening  of  the  meatus  auditorius  has  been  already  de- 
scribed 

The  fenestra  ovalis  (fenestra  vestibuli)  is  a  reniform  opening, 
situated  at  the  bottom  of  a  small  oval  fossa  (the  pelvis  ovalis),  in 
the  upper  part  of  the  inner  wall  of  the  tympanum,  directly  oppo- 
site the  meatus.  The  long  diameter  of  the  fenestra  is  directed 
horizontally,  and  its  convex  borders  upwards.  It  is  the  opening 
of  communication  between  the  tympanum  and  vestibule,  and  is 
closed  by  the  foot  of  the  stapes  and  by  the  lining  membrane  of 
both  cavities. 

The  fenestra  rotunda  (fenestra  cochlea?)  is  somewhat  triangular 
in  its  form,  and  situated  in  the  inner  wall  of  the  tympanum,  below 
and  rather  posteriorly  to  the  fenestra  ovalis,  from  which  it  is 


Fig.  87. 


THE  TYMPANUM  OF  THE  LEFT 
EAR. — 1.  Its  inner  wall.  2.  A 
convex  ridge  marking  the  situa- 
tion of  the  aqueductus  Fallopii ; 
the  star  shows  its  termination 
on  the  face  of  the  section,  in  its 
course  downwards  to  the  stylo  - 
mastoid  foramen.  3.  The  fe- 
nestra ovalis.  4.  The  promon- 
tory. 5.  The  fenestra  rotunda. 
Anteriorly  (6)  is  the  entrance 
of  the  Eustachian  tube.  7.  The 
opening  for  the  tensor  tympani. 
8.  The  opening  for  the  laxator 
tympani ;  and  (9)  the  opening 
of  exit  for  the  chorda  tympani 
nerve.  Posteriorly  (10)  is  the 

opening  of  entrance  for  the  chorda  tympani  ;  and  (11)  the  pyramid  with  the 
small  opening  at  its  apex  which  gives  passage  to  the  tendon  of  the  stapedius 
muscle.  Superiorly  is  a  large  opening  (12)  leading  backwards  to  the  mastoid 
cells. 


separated  by  a  bony  elevation,  called  the  promontory.     It  serves 
to  establish  a  communication  between  the  tympanum  and  the 


TYMPANUM.  277 

cochlea.     In  the  fresh  subject  it  is  closed  by  a  proper  membrane 
(m.  tympani  secundaria),  as  well  as  by  the  lining  of  both  cavities. 

The  mastoid  cells  are  numerous,  and  occupy  the  whole  of  the 
interior  of  the  mastoid  process  and  part  of  the  petrous  bone. 
They  communicate  by  a  large  irregular  opening  with  the  upper 
and  posterior  circumference  of  the  tympanum. 

The  Eustachian  tube  is  a  short  canal  about  an  inch  and  three- 
quarters  in  length,  extending  obliquely  between  the  pharynx  and 
the  anterior  circumference  of  the  tympanum.  In  structure  it  is 
partly  fibro-cartilaginous  and  partly  osseous,  is  broad  and  ex- 
panded at  its  pharyngeal  extremity,  and  narrow  and  compressed 
at  the  tympanum. 

The  smaller  openings  serve  for  the  transmission  of  the  chorda 
tympani  nerve,  and  three  of  the  muscles  of  the  tympanum. 

The  opening  by  which  the  chorda  tympani  enters  the  tympa- 
num is  at  about  the  middle  of  its  posterior  wall,  and  near  the 
root  of  the  pyramid.  The  opening  of  exit  for  the  chorda  tym- 
pani is  at  the  fissura  Glaseri  in  the  anterior  wall  of  the  tympa- 
num. 

The  opening  for  the  laxator  tympani  muscle  is  also  situated  in 
the  fissura  Glaseri,  in  the  anterior  wall  of  the  tympanum.  The 
opening  for  the  tensor  tympani  muscle  is  in  the  inner  wall,  im- 
mediately above  the  opening  of  the  Eustachian  tube.  The  open- 
ing for  the  stapedius  muscle  is  at  the  apex  of  a  conical  bony 
eminence,  called  the  pyramid,  which  is  situated  on  the  poste- 
rior wall  of  the  tympanum,  immediately  behind  the  fenestra 
ovalis. 

Directly  above  the  fenestra  ovalis  is  a  rounded  ridge  formed  by 
the  projection  of  the  aquceductus  Fallopii.  Beneath  the  fenestra 
ovalis  and  separating  it  from  the  fenestra  rotunda  is  the  pro- 
montory, a  rounded  prominence  formed  by  the  projection  of  the 
first  turn  of  the  cochlea.  It  is  channelled  upon  its  surface  by 
three  small  grooves,  which  lodge  the  three  tympanic  branches  of 
Jacobson's  nerve. 

The/orawma  and  processes  of  the  tympanum  may  be  arranged, 
according  to  their  situation,  into  four  groups. 

1.  In  the  external  wall  is  the  meatus  auditorius,  closed  by  the 
membrana  tympani. 

2.  In  the  inner  wall,  from  above  downwards,  are  the — 

Opening  for  the  tensor  tympani, 
Ridge  of  the  aquaeductus  Fallopii, 
Fenestra  ovalis, 

Promontory,  with  the  grooves  for  Jacobson's  nerve, 
Fenestra  rotunda. 
24 


278  THE   DISSECTOR. 

3.  In  the  posterior  wall  are  the — 

Opening  of  the  mastoid  cells, 
Pyramid,  and  opening  for  the  stapedius, 
Opening  for  Jacobson's  nerve. 
Apertura  chordae  (entrance). 

4.  In  the  anterior  wall  are  the — 

Eustachian  tube, 

Fissura  Glaseri, 

Opening  for  laxator  tyrapani, 

Apertura  chordae  (exit). 

The  tympanum  is  lined  by  a  vascular  mucous  membrane, 
which  invests  the  ossicula  and  chorda  tympani,  and  forms  the 
internal  layer  of  the  membrana  tympani.  From  the  tympanum 
it  is  reflected  into  the  mastoid  cells,  which  it  lines  throughout, 
and  it  passes  through  the  Eustachian  to  become  continuous  with 
the  mucous  membrane  of  the  pharynx.  In  the  Eustachian  tube 
it  is  furnished  with  vibratile  cilia. 

Vessels  and  Nerves. — The  arteries  of  the  tympanum  are  de- 
rived from  the  internal  maxillary,  internal  carotid,  and  posterior 
auricular. 

Its  nerves  are — 1.  Minute  branches  from  the  facial,  which  are 
distributed  to  the  stapedius  muscle.  2.  The  chorda  tympani, 
which  leaves  the  facial  nerve  near  the  stylo-mastoid  foramen,  and 
arches  upwards  to  enter  the  tympanum  at  the  root  of  the  pyra- 
mid ;  it  then  passes  forwards  between  the  handle  of  the  malleus 
and  long  process  of  the  incus,  to  its  proper  opening  in  the 
fissura  Glaseri.  3.  The  tympanic  branches  of  Jacobson's  nerve, 
which  are  distributed  to  the  membranes  of  the  fenestra  ovalis 
and  fenestra  rotunda,  and  to  the  Eustachian  tube,  and  form  a 
plexus  by  communicating  with  the  carotid  plexus,  otic  ganglion, 
and  Vidian  nerve.  4.  A  filament  from  the  otic  ganglion  to  the 
tensor  tympani  muscle. 

INTERNAL   EAR. 

The  internal  ear  is  called  labyrinth,  from  the  complexity  of  its 
communications ;  it  consists  of  a  membranous  and  an  osseous 
portion.  The  osseous  labyrinth  presents  a  series  of  cavities, 
which  are  channelled  through  the  substance  of  the  petrous  bone, 
and  is  situated  between  the  cavity  of  the  tympanum  and  the 
meatus  auditorius  internus.  It  is  divisible  into  the — 

Yestibule,         Semicircular  canals,         Cochlea. 

The  VESTIBULE  is  a  small  three-cornered  cavity,  compressed 
from  without  inwards,  and  situated  immediately  within  the  inner 


INTERNAL  EAR.  279 

wall  of  the  tympanum.  The  three  corners,  which  are  named 
ventricles  or  cornua,  are  placed — one  anteriorly,  one  superiorly, 
and  one  posteriorly. 

The  anterior  ventricle  receives  the  oval  aperture  of  the  scala 
vestibuli ;  the  superior,  the  ampullary  openings  of  the  superior 
and  horizontal  semicircular  canals ;  the  posterior,  the  ampullary 
opening  of  the  oblique  semicircular  canal,  the  common  aperture 
of  the  oblique  and  perpendicular  canals,  the  termination  of  the 
horizontal  canal,  and  the  aperture  of  the  aqureductus  vestibuli. 

Fig.  88. 


A  VIEW  OP  THE  LABYRINTH  OF  THE  LEFT  EAR  OF  A  FOETUS  OF  EIGHT  MONTHS, 

AS  SEEN  FROM  ABOVE.    MAGNIFIED  FOUR  DIAMETERS. 1,  2,  3.  The  COChlea.    1, 

1.  Its  first  turn.  2,  2.  Its  second  turn.  3,  3.  Its  third  or  half  turn,  and  apex 
or  cupola.  4.  The  fenestra  rotunda.  5.  The  fenestra  ovalis.  6.  The  groove 
around  it.  7,  7.  The  vestibule.  8,  9,  10.  The  posterior  semicircular  canal,  with 
its  ampulla  at  8.  11,  11.  The  superior  semicircular  canal.  12.  The  external 
semicircular  canal. 

In  the  anterior  ventricle  is  a  small  depression,  which  corresponds 
with  the  posterior  segment  of  the  cul-de-sac  of  the  meatus  audi- 
torius  internus;  it  is  called  i\\z  fovea  hemispherica,  and  is  pierced 
by  a  cluster  of  small  openings,  the  macula  cribrosa.  In  the  su- 
perior ventricle  of  the  vestibule  is  another  small  depression,  the 
fovea  elliptica,  which  is  separated  from  the  fovea  hemispherica 
by  a  projecting  crest,  the  eminentia  pyramidalis.  The  latter  is 
pierced  by  numerous  minute  openings  for  the  passage  of  nervous 
lihuuents.  The  posterior  ventricle  presents  a  third  small  depres- 
sion, the  fovea  sulciformis,  which  leads  upwards  to  the  ostium 


280  THE   DISSECTOR. 

aquseductus  vestibuli.  The  internal  wall  of  the  vestibule  corre- 
sponds with  the  bottom  of  the  cul-de-sac  of  the  meatus  audito- 
rius  interims,  and  is  pierced  by  numerous  small  openings  for  the 

Fig.  89. 

THE  LABYRINTH'OF  THE  LEFT  EAR. — 1.  The 
vestibule.  2.  The  fenestra  ovalis,  in  its  natural 
position,  looking  from  the  meatus  auditorius 
externus ;  the  entrance  into  the  vestibule  from 
the  tympanum.  3.  The  perpendicular  semicircu- 
lar canal.  4.  Its  ampulla.  5.  Its  union  with 
the  oblique  canal.  6.  The  oblique  semicircular 
canal.  7.  Its  ampulla.  8.  The  horizontal  se- 
micircular canal.  9.  Its  ampulla.  10.  The 
cochlea,  internal  to  and  rather  in  front  of  the 
vestibule.  11.  The  fenestra  rotunda,  the  en- 
trance into  the  scala  tympani  of  the  cochlea. 
12.  The  canal  of  the  cochlea  leading  from  the 
fenestra  rotunda  to  make  its  first  turn.  13.  The 
extremity  of  the  canal  called  the  cupola. 

transmission  of  nervous  filaments.  In  the  external  or  tympanic 
wall  is  the  reniform  opening  of  the  fenestra  ovalis  (fenestra  ves- 
tibuli),  the  margin  of  which  presents  a  prominent  rim  towards 
the  cavity  of  the  vestibule. 

The  openings  of  the  vestibule  may  be  arranged,  like  those  of 
the  tympanum,  into  large  and  small. 

The  large  openings  are  seven  in  number,  viz  :  the — 
Fenestra  ovalis, 
Scala  vestibuli, 

Five  openings  of  the  three  semicircular  canals. 
The  small  openings  are  the — 
Aquaeductus  vestibuli, 
Openings  for  small  arteries, 
Openings  for  branches  of  the  auditory  nerve. 
The  fenestra  ovalis  has  already  been  described  ;  it  is  the  open- 
ing from  the  tympanum. 

The  opening  of  the  scala  vestibuli  is  the  oval  termination  of 
the  vestibular  canal  of  the  cochlea. 

The  aquceductus  vestibuli  (canal  of  Cotunnius)1  is  the  com- 
mencement of  the  small  canal  which  opens  under  the  osseous 
scale  on  the  posterior  surface  of  the  petrous  bone.  It  gives  pas- 
sage to  a  process  of  membrane  (which  is  continuous  internally 
with  the  lining  membrane  of  the  vestibule,  and  externally  with 
the  dura  mater),  and  to  a  small  vein. 

1  Dominico  Cotunnius,  an  Italian  physician;  Ms  dissertation,  "De 
Aquseductibus  Auris  Humanae  Internse,"  was  published  in  Naples  in 
1761. 


COCHLEA.  281 

The  openings  for  arteries  and  nerves  are  situated  in  the  internal 
wall  of  the  vestibule,  and  correspond  with  the  termination  of  the 
meatus  auditorius  internus. 

The  SEMICIRCULAR  CANALS  are  three  bony  passages  communi- 
cating with  the  vestibule,  into  which  they  open  by  both  extremi- 
ties. Near  one  extremity  of  each  of  the  canals  is  a  dilatation  of 
its  cavity,  which  is  called  the  ampulla  (sinus  ampullaceus).  The 
superior,  or  perpendicular  canal  (canalis  semicircularis  verticalis 
superior),  is  directed  transversely  across  the  petrous  bone,  form- 
ing a  projection  on  the  anterior  face  of  the  latter.  It  commences, 
by  means  of  an  ampulla,  in  the  superior  ventricle  of  the  vestibule, 
and  terminates  posteriorly  by  joining  with  the  oblique  and  form- 
ing a  common  canal  which  opens  into  the  upper  part  of  the  pos- 
terior ventricle.  The  middle  or  oblique  canal  (canalis  semicircu- 
laris verticalis  posterior)  corresponds  with  the  posterior  part  of 
the  petrous  portion  of  the  temporal  bone ;  it  commences  by  an 
ampullary  dilatation  in  the  posterior  ventricle,  and  curves  nearly 
perpendicularly  upwards  to  terminate  in  the  common  canal.  In 
the  ampulla  of  this  canal  are  numerous  minute  openings  for 
nervous  filaments.  The  inferior  or  horizontal  canal  (canalis  semi- 
circularis horizontalis)  is  directed  outwards  towards  the  base  of 
the  petrous  bone,  and  is  shorter  than  the  two  preceding.  It 
commences  by  an  ampullary  dilatation  in  the  superior  ventricle, 
and  terminates  in  the  posterior  ventricle. 

The  COCHLEA  (snail-shell)  forms  the  anterior  portion  of  the 
labyrinth,  corresponding  by  its  apex  with  the  anterior  wall  of 
the  petrous  bone,  and  by  its  base  with  the  anterior  depression  at 
the  bottom  of  the  cul-de-sac  of  the  *eatus  auditorius  internus. 
It  consists  of  an  osseous  and  gradually  tapering  canal,  about  one 
inch  and  a  half  in  length,  which  makes  two  turns  and  a  half  spi- 
rally around  a  central  axis,  called  the  .modiolus. 

The  central  axis,  or  modiolus,  is  large  near  its  base,  where  it 
corresponds  with  the  first  turn  of  the  cochlea,  and  diminishes  in 
diameter  towards  its  extremity.  At  its  base,  it  is  pierced  by 
numerous  minute  openings,  which  transmit  the  filaments  of  the 
cochlear  nerve.  These  openings  are  disposed  in  a  spiral  manner  : 
hence  they  have  received,  from  Cotunnius,  the  name  of  tractus 
spiralis  foraminulentus.  The  modiolus  is  everywhere  traversed, 
in  the  direction  of  its  length,  by  minute  canals,  which  proceed 
from  the  tractus  spiralis  foraminulentus,  and  terminate  upon  the 
sides  of  the  modiolus,  by  opening  into  the  canal  of  the  cochlea 
or  upon  the  surface  of  its  lamina  spiralis.  The  central  canal  of 
the  tractus  spiralis  foraminulentus  is  larger  than  the  rest,  and  is 
named  the  tubulus  centralis  modioli ;  it  is  continued  onwards  to 
the  extremity  of  the  modiolus,  and  transmits  a  nerve  and  small 
artery  (arteria  centralis  modioli). 

24* 


282  THE   DISSECTOR. 

The  interior  of  the  canal  of  the  cochlea  is  partially  divided  into 
two  passages  (scalae)  by  means  of  a  thin  and  porous  lamina  of 
bone  (zonula  ossea  laminae  spiralis),  which  is  wound  spirally 
around  the  modiolus,  in  the  direction  of  the  canal.  The  bony 
septum  extends  for  about  two-thirds  across  the  diameter  of  the 
canal,  and  in  the  fresh  subject  is  prolonged  to  the  opposite  wall 
by  means  of  a  membranous  layer,  so  as  to  constitute  a  complete 
partition,  the  lamina  spiralis.  This  osseous  lamina  spiralis  con- 
sists of  two  thin  Iamella3  of  bone,  between  which,  and  through 
the  perforations  on  their  surfaces,  the  filaments  of  the  cochlear 
nerve  reach  the  membrane  of  the  cochlea.  At  the  apex  of  the 
cochlea,  the  lamina  spiralis  terminates  by  a  pointed,  hook-shaped 
process,  the  haniulus  laminae  s-piralis.  The  two  scalae  of  the 
cochlea,  which  are  completely  separated  throughout  their  length 
in  the  living  ear,  communicate  superiorly,  over  the  hamulus  laminae 
spiralis,  by  means  of  an  opening  common  to  both,  which  has  been 
termed  by  Breschet  helico-trema  (e'3ii|,  tXi'crtfw,  volvere — fpr^a}. 
Inferiorly,  one  of  the  two  scalae,  the  scala  vestibuli,  terminates 
by  means  of  an  oval  aperture  in  the  anterior  ventricle  of  the  ves- 
tibule ;  whi4e  the  other,  the  scala  tympani,  becomes  somewhat 
expanded,  and  opens  into  the  tympanum  through  the  fenestra 
rotunda  (fenestra  cochleae).  Near  the  termination  of  the  scala 
tympani  is  the  small  opening  of  the  aquaeductus  cochleae. 

The  internal  surface  of  the  osseous  labyrinth  is  lined  by  &fibro- 
serous  membrane,  which  is  analogous  to  the  dura  mater  in  per- 
forming the  office  of  a  periosteum  by  its  exterior,  whilst  it  fulfils 
the  purpose  of  a  serous  membrane  by  its  internal  layer,  secreting 
a  limpid  fluid,  the  aqua  la^byrinthi  (perilymph,  liquor  Cotunnii), 
and  sending  a  reflection  inwards  upon  the  nerves  distributed  to 
the  membranous  labyrinth.  In  the  cochlea,  the  membrane  of  the 
labyrinth  invests  the  two  surfaces  of  the  bony  lamina  spiralis,  and 
being  continued  from  its  border  across  the  diameter  of  the  canal 
to  its  outer  wall,  forms  the  membranous  lamina  spiralis,  and  com- 
pletes the  separation  between  the  scala  tympani  and  scala  vestibuli. 
The  fenestra  ovalis  and  fenestra  rotunda  are  closed  by  an  extension 
of  this  membrane  across  them,  assisted  by  the  membrane  of  the 
tympanum,  and  a  proper  intermediate  layer.  Besides  lining  the 
interior  of  the  osseous  cavity,  the  membrane  of  the  labyrinth  sends 
two  delicate  processes  along  the  aqueducts  of  the  vestibule  and 
cochlea,  to  the  internal  surface  of  the  dura  mater,  with  which  they 
are  continuous.  These  processes  are  the  remains  of  communica- 
tion originally  subsisting  between  the  dura  mater  and  the  cavity 
of  the  labyrinth.1 

1  Cotunnius  regarded  these  processes  as  tubular  canals,  through  which, 
the  superabundant  aqua  labyrinth!  might  be  expelled  into  the  cavity  of 


MEMBRANOUS   LABYRINTH.  283 

The  MEMBRANOUS  LABYRINTH  is  smaller  in  size,  but  a  perfect 
counterpart,  with  respect  to  form,  of  the  vestibule  and  semicircular 
canals.  Its  consists  of  a  small  elongated  sac,  sacculus  communis 
(utriculus  communis) ;  of  three  semicircular  membranous  canals, 
which  correspond  with  the  osseous  canals,  and  communicate  with 
the  sacculus  communis  ;  and  of  a  small  round  sac  (sacculus  pro- 
prius),  which  occupies  the  anterior  ventricle  of  the  vestibule,  and 
lies  in  close  contact  with  the  external  surface  of  the  sacculus 
communis.  The  membranous  semicircular  canals  are  two-thirds 
smaller  in  diameter  than  the  osseous  canals. 

The  membranous  labyrinth  is  retained  in  position  by  means  of 
the  numerous  nervous  filaments  which  are  distributed  to  it  from 
the  openings  of  the  inner  wall  of  the  vestibule,  and  is  separated 
from  the  lining  membrane  of  the  labyrinth,  by  the  aqua  labyrinthi. 
In  structure  it  is  composed  of  four  layers ;  an  external  or  serous 
layer,  derived  from  the  lining  membrane  of  the  labyrinth ;  a 
vascular  layer,  in  which  an  abundance  of  minute  vessels  are  dis- 
tributed ;  a  nervous  layer,  formed  by  the  expansion  of  the  fila- 
ments of  the  vestibular  nerve ;  and  an  internal  and  serous  mem- 
brane, by  which  the  limpid  fluid  which  fills  its  interior  is  secreted. 
Some  patches  of  pigment  have  been  observed  by  Wharton  Jones, 
in  the  tissue  of  the  membranous  labyrinth  of  man.  Among  ani- 
mals such  spots  are  constant. 

The  membranous  labyrinth  is  filled  with  a  limpid  fluid,  first 
well  described  by  Scarpa,  and  thence  named  liquor  Scarpae  (endo- 
lymph,  vitreous  humor  of  the  ear),  and  contains  two  small  cal- 
careous masses  called  otoconites.  The  otoconites  (ot>$,  U.TOJ,  xovij, 
the  ear-dust)  consist  of  an  assemblage  of  minute,  crystalline  par- 
ticles of  carbonate  and  phosphate  of  lime,  held  together  by  ani- 
mal substance,  and  probably  retained  in  form  by  a  reflection  of 
the  lining  membrane  of  the  membranous  labyrinth.  They  are 
found  suspended  in  the  liquor  Scarpae  ;  one  in  the  sacculus  com- 
munis, the  other  in  the  sacculus  proprius,  from  that  part  of  each 
sac  with  which  the  nerves  are  connected. 

The  AUDITORY  NERVE  divides  into  two  branches  at  the  bottom 
of  the  cul-de-sac  of  the  meatus  auditorius  interims  ;  a  vestibular 
nerve,  and  a  cochlear  nerve.  The  vestibular  nerve,  the  posterior 
of  the  two,  divides  into  three  branches,  superior,  middle,  and  in- 
ferior. The  superior  vestibular  branch  gives  off  a  number  of  fila- 

the  cranium.  Wharton  Jones,  in  the  article  "  Organ  of  Hearing,"  in  the 
Cyclopaedia  of  Anatomy  and  Physiology,  also  describes  them  as  tubular 
canals  which  terminate  beneath  the  dura  mater  of  the  petrous  bone  in  a 
small  dilated  pouch.  In  the  ear  of  a  man  deaf  and  dumb  from  birth,  he 
found  the  termination  of  the  aqueduct  of  the  vestibule  of  unusually  large 
size,  in  consequence  of  irregular  development. 


284  THE   DISSECTOR. 

ments  which  pass  through  the  minute  openings  of  the  eminentia 
pyramidalis  and  superior  ventricle  of  the  vestibule,  and  are  dis- 
tributed to  the  sacculus  communis  and  ampullse  of  the  perpendi- 
cular and  horizontal  semicircular  canals.  The  middle  vestibular 
branch  sends  off  numerous  filaments,  which  pass  through  the 
openings  of  the  macula  cribrosa  in  the  anterior  ventricle  of  the 
vestibule,  and  are  distributed  to  the  sacculus  proprius.  The  in- 
ferior and  smallest  branch  takes  its  course  backwards  to  the  pos- 
terior wall  of  the  vestibule,  and  gives  off  filaments,  which  pierce 
the  wall  of  the  ampullary  dilatation  of  the  oblique  canal,  to  be 
distributed  upon  its  ampulla.  According  to  Stiefensand,  there 
is,  in  the  situation  of  the  point  of  entrance  of  the  nervous  filaments 
into  the  ampulla,  a  deep  depression  upon  the  exterior  of  the  mem- 
brane, and  upon  the  interior  a  corresponding  projection,  which 
forms  a  kind  of  transverse  septum,  partially  dividing  the  cavity 
of  the  ampulla  into  two  chambers.  In  the  substances  of  the 
sacculi  and  ampullae,  the  nervous  filaments  radiate  in  all  direc- 
tions, anastomosing  with  each  other,  and  forming  interlacements 
and  loops ;  and  they  terminate  upon  the  inner  surface  of  the 
membrane  in  minute  papillae,  resembling  those  of  the  retina. 

The  cochlear  nerve  divides  into  numerous  filaments  which  enter 
the  foramina  of  the  tractus  spiralis  foraminulentus  in  the  base  of 
cochlea,  and  passing  upwards  in  the  canals  of  the  modiolus,  bend 
outwards  at  right  angles,  to  be  distributed  in  the  tissue  of  the 
lamina  spiralis.  The  central  portion  of  the  nerve  passes  through 
the  tubulus  centralis  of  the  modiolus,  and  supplies  the  apicial 
portion  of  the  lamina  spiralis.  In  the  lamina  spiralis,  the  nervous 
filaments,  lying  side  by  side,  on  an  even  plane,  form  numerous 
anastomosing  loops,  and  spread  out  into  a  nervous  membrane. 
According  to  Treviranus  and  Gottsche,  the  ultimate  termina- 
tions of  the  filaments  assume  the  form  of  papillae. 

The  arteries  of  the  labyrinth  are  derived  from  the  internal 
auditory  branch  of  the  superior  cerebellar  or  basilar  artery,  and 
from  the  stylo-mastoid. 

MOUTH  AND  TONGUE. 

In  the  section  of  the  nasal  fossae  the  incision  was  carried  through  the 
roof  of  the  mouth,  and  the  division  of  the  soft  palate  was  completed  by 
an  incision  made  with  a  scalpel.  Care  was  taken  not  to  disturb  the  cavity 
of  the  mouth  any  more  than  was  necessary.  We  have  now  to  study 
that  cavity,  together  with  the  tongue,  for  which  purpose  any  fragments 
of  the  preceding  dissection,  which  may  obscure  the  view,  should  be 
removed  ;  and  that  side  of  the  mouth  selected  for  examination  which 
has  been  least  injured. 

The  mouth  is  the  irregular  cavity  which  contains  the  organ 
of  taste,  and  the  principal  instruments  of  mastication.  It  is 


LIPS — CHEEKS — PALATE. 


285 


bounded,  in  front,  by  the   lips ;  Fig.  90. 

on  either  side,  by-  the  internal 
surface  of  the  cheeks  ;  above,  by 
the  hard  palate  and  teeth  of  the 
upper  jaw  ;  below,  by  the  tongue, 
by  the  mucous  membrane  stretched 
between  the  arch  of  the  lower  jaw 
and  the  under  surface  of  the 
tongue,  and  by  the  teeth  of  the 
inferior  maxilla ;  and,  behind,  by 
the  soft  palate  and  fauces. 
*  The  lips  are  two  fleshy  folds 
formed  externally  by  common  in- 
tegument, and  internally  by  mu- 
cous membrane,  and  containing 
between  these  two  layers,  muscles, 
a  quantity  of  fat,  and  numerous 
small  labial  glands.  They  are 
attached  to  the  surface  of  the 
upper  and  lower  jaw  ;  and  each 
lip  is  connected  to  the  gum  in  the 
middle  line  by  a  fold  of  mucous 

membrane,  the  frcenum  labii  supe-       THE i  TONGUE  WITH  IT s  PAPILLA . 

.      .  '-      J        7   r  •••/•••       — 1.    The    raphe\  which    in    some 

nons,  andfranum  labii  infenons,    tongues  bifurcates  on  the  dorsum  of 

the  former  being  the  larger  of  the  the  organ,  as  in  the  figure.    2,  2. 

^wo  The    lobes    of   the    tongue.       The 

mu         r     7      /u  \  rounded  eminences  on  this  part  of 

The   cheeks  (buccae)   are   con-   the  orgaD(  and  near  its_tip  are  the 
tinuous  on  either  hand  with  the 
lips,  and  form  the  sides  of  the 
face  ;  they  are  composed  of  in- 
tegument, a  large  quantity  of  fat,    tongue.    4,  4.    Its  sides,  on  which 
muscles,  mucous  membrane,  and  are  8een  the  lameiiated  and  fringed 

i  /     7      j  papillae.     5, 5.  The  V-shaped  row  of 

buccal  glands.  papillae  circumvallate.    6.  The  fora- 

The    muCOUS    membrane   lining    men  csecum.    7.  The  mucous  glands 

the  cheeks  is  reflected  above  and  of  the  roots  of  the  tongue.    8.  The 

below  upon  the  sides  of  the  jaws,  •gg0"?,',  iV™?  grS  ?o±a 

and  is  attached  posteriorly  to  the  of  the  os  hyoides. 

anterior  margin  of  the  ramus  of 

the  lower  jaw.     At  about  its  middle,  opposite  the  second  molar 

tooth  of  the  upper  jaw,  is  a  papilla,  upon  which  may  be  observed 

a  small  opening,  the  aperture  of  the  duct  of  the  parotid  gland. 

The  hardpalate  is  a  dense  structure,  composed  of  mucous  mem- 
brane, palatal  glands,  fibrous  tissue,  vessels,  and  nerves,  and 
firmly  connected  to  the  palate  processes  of  the  superior  maxillary 
and  palate  bones.  It  is  bounded  in  front  and  on  each  side  by  the 
alveolar  processes  and  gums,  and  is  continuous  behind  with  the 


papillae  fungiformes.  The  smaller 
papilla,  among  which  the  former  are 
dispersed,  are  the  papillae  conicw 
and  filiformes.  3.  The  tip  of  the 


286  THE   DISSECTOR. 

soft  palate.  Along  the  middle  line  it  is  marked  by  an  elevated 
raphe,  and  presents,  upon  each  side  of  the  raphe,  a  number  of 
transverse  ridges  and  grooves.  Near  its  anterior  extremity,  and 

Fig.  91. 


a'  P  0  a/          *       ** 

VARIOUS  FORMS  OF  THE  CONICAL  COMPOUND  PAPILLAE,  DEPRIVED  OF  THEIR 
EPITHELIUM  : — a,  b,  and  especially  c,  are  the  best  marked,  and  were  provided 
with  the  stiffest  and  longest  epithelium ;  their  simple  papillae  are  more  acumi- 
nated, d,  approaches  the  fungiform  variety  :  e,  f,  come  near  the  simple 
papillae. — Magnified  20  diameters. 

immediately  behind  the  middle  incisor  teeth,  is  a  papilla  which 
corresponds  with  the  termination  of  the  anterior  palatine  canal, 
and  receives  the  naso-palatine  nerves. 

The  vessels  and  nerves  of  the  hard  palate  are  the  descending 
palatine  artery  (page  175),  and  nerves  (page  183),  which  emerge 
at  the  posterior  palatine  foramina  and  pass  forwards,  and  the 
naso-palatine  nerve  (page  183),  and  artery  of  the  septum  (page 
115),  in  front. 

If  the  mucous  membrane  be  torn  away  from  the  side  of  the  nasal 
fossa,  at  its  posterior  part,  so  as  to  expose  the  ascending  portion  of  the 
palate  bone  and  spheno-palatine  foramen,  the  descending  palatine  artery 
and  accompanying  nerves  may  be  seen  through  the  thin  plate  of  bone. 
This  plate  should  be  removed,  and  the  artery  and  nerve  followed  in  their 
course  downwards  to  the  posterior  palatine  foramen,  and  from  that  point 
forwards  in  the  substance  of  the  palate.  The  artery  and  nerve  lie  deeply 
in  the  palate,  and  for  a  part  of  their  course  in  a  groove  on  the  bone.  At 
the  same  time  the  two  other  palatine  nerves,  middle  and  posterior  (page 
183),  may  be  dissected  and  traced  to  their  distribution,  the  middle  to  the 
tonsil  and  soft  palate  ;  the  posterior  to  the  posterior  part  of  the  palate  as 
well  as  to  the  soft  palate  and  tonsil. 

The  gums  are  composed  of  a  thick  and  dense  mucous  mem- 
brane, which  is  closely  adherent  to  the  periosteum  of  the  alveolar 
processes,  and  embraces  the  necks  of  the  teeth.  They  are 
remarkable  for  their  hardness  and  insensibility;  and  for  their 
close  contact,  without  adhesion,  to  the  surface  of  the  tooth. 
From  the  neck  of  the  tooth  they  are  reflected  into  the  alveolus, 
and  become  continuous  with  the  periosteal  (peridental)  mem- 
brane of  that  cavity. 

TONGUE. — The  tongue  is  invested  by  mucous  membrane,  which 


THE   TONGUE.  287 

is  reflected  from  its  under  part  upon  the  inner  surface  of  the  lower 
jaw,  and  constitutes,  with  the  muscles  beneath,  the  floor  of  the 
mouth.  Upon  the  under  surface  of  the  tongue,  near  its  anterior 
part,  the  mucous  membrane  forms  a  considerable  fold,  which  is 
called  the  frcenum  linguae;  and  on  each  side  of  the  fraenum  is  a 
large  papilla,  the  commencement  of  the  duct  of  the  submaxillary 
gland  (Wharton's  duct).  Running  back  from  this  papilla  is  a 
ridge,  occasioned  by  the  prominence  of  the  sublingual  gland ; 
and  opening  upon  the  summit  of  this  ridge,  a  number  of  small 
openings,  the  apertures  of  the  excretory  ducts  of  the  gland. 
Posteriorly  the  tongue  is  connected  with  the  os  hyoides  by  muscle, 
and  to  the  epiglottis  by  three  folds  of  mucous  membrane,  called 
\hefrcena  epiglottidis. 

The  mucous  membrane  of  the  mouth  is  continuous  with  the  derma  along 
the  margin  of  the  lips.  On  either  side  of  the  fraenum  linguae  it  may  be 
traced  through  the  sublingual  ducts,  and  along  Wharton's  ducts  into  the 
submaxillary  glands.  From  the  sides  of  the  cheeks  it  passes  through 
the  opening  of  Stenon's  ducts  to  the  parotid  glands.  In  the  fauces  it 
forms  the  assemblage  of  follicles  called  tonsils,  and  may  thence  be  traced 
downwards  into  the  larynx  and  pharynx,  where  it  is  continuous  with  the 
general  gastro-pulmonary  mucous  membrane. 

Beneath  the  mucous  membrane  are  a  number  of  small  glandular 
granules,  which  pour  their  secretion  upon  the  surface.  A  con- 
siderable number  of  these  bodies  are  situated  within  the  lips,  in 
the  palate,  and  in  the  floor  of  the  mouth.  They  are  named,  ac- 
cording to  their  position,  labial  glands,  palatial  glands,  and  buccal 
glands. 

The  surface  of  the  tongue  is  covered  by  a  dense  layer,  analogous 
to  the  corium  of  the  skin,  which  gives  support  to  papillae.  A 
raphe  marks  the  middle  line  of  the  organ,  and  divides  it  into 
symmetrical  halves. 

The  papilla  of  the  tongue  are  the — 

Papillae  circumvallatae,  Papilla)  filiformes, 

Papillae  conicae,  Papillae  fungiformes. 

The  papilla  circumvallatce  (p.  lenticulares)  are  of  large  size, 
and  from  fifteen  to  twenty  in  number.  They  are  situated  on  the 
dorsum  of  the  tongue,  near  its  root,  and  form  a  row  on  each  side, 
which  meets  its  fellow  at  the  middle  line,  like  the  two  branches 
of  the  letter  A.  Each  papilla  resembles  a  cone,  attached  by  its 
apex  to  the  bottom  of  a  cup-shaped  depression  :  hence  they  are 
also  named  papillae  calyciformes.  This  cup-shaped  cavity  forms 
a  kind  of  fossa  around  the  papilla,  whence  their  name,  circum- 
vallatce. At  the  meeting  of  the  two  rows  of  these  papillae  upon 
the  middle  of  the  root  of  the  tongue,  is  a  deep  mucous  follicle, 
called  foramen  ccecum. 

The  papillce  conica  and  filiformes  cover  the  whole  surface  of 


288  THE  DISSECTOR. 

the  tongue  in  front  of  the  circumvallatse,  but  are  most  abundant 
towards  its  anterior  part.  They  are  conical  and  filiform  in  shape, 
and  many  of  them  are  pierced  at  the  extremity  by  a  minute  aper- 
ture. Hence  they  may  be  regarded  as  follicles,  rather  than  sentient 
organs ;  the  true  sentient  papill*  being  extremely  minute,  and 
occupying  their  surface  as  they  do  that  of  the  other  papilla  of 
the  tongue. 

The  papillae  fungiformes  (p.  capitatae)  are  irregularly  dispersed 
over  the  dorsum  of  the  tongue,  and  are  easily  recognized  among 
the  other  papillae  by  their  rounded  heads,  larger  size,  and  red 
color.  A  number  of  these  papillae  will  generally  be  observed  at 
the  tip  of  the  tongue. 

Behind  the  papilla  circumvallataa,  at  the  root  of  the  tongue, 
are  a  number  of  mucous  glands  (lingual),  which  open  upon  the 
surface.  There  is  also  a  small  cluster  beneath  the  tip  of  the 
tongue. 

In  structure  the  tongue  is  composed  of  muscular  fibres,  which  are  dis- 
tributed in  layers  arranged  in  various  directions  :  thus,  some  are  disposed 
longitudinally  (lingualis  superficialis)  ;  others  transversely  (lingualis 
trans  versus)  ;  others,  again,  obliquely  and  vertically.  Between  the  mus- 
cular fibres  is  a  considerable  quantity  of  adipose  substance,  and  in  the 
middle  of  the  organ  a  vertical  septum  of  fibrous  tissue. 

Vessels  and  Nerves. — The  tongue  is  abundantly  supplied  with 
blood  by  the  lingual  arteries. 

The  nerves  are  three  in  number,  and  of  large  size  :  the  gustatory 
branch  of  the  inferior  maxillary,  which  is  distributed  to  the  pa- 
pillae, and  is  the  nerve  of  common  sensation  and  taste  ;  the  glosso- 
pharyngeal,  which  is  distributed  to  the  mucous  membrane,  glands, 
and  papillae  circumvallatse  ;  and  the  hypoglossal,  which  is  the  motor 
nerve  of  the  tongue,  and  is  distributed  to  the  muscles. 

THE  LARYNX. 

The  larynx  is  situated  at  the  fore-part  of  the  neck,  between  the 
trachea  and  the  base  of  the  tongue.     It  is  a  short  tube,  having 
an  hour-glass  form,  and  is  composed  of  cartilages,  ligaments, 
muscles,  vessels,  nerves,  and  mucous  membrane. 
The  cartilages  are  the — 

Thyroid,  Two  cornicula  laryngis, 

Crycoid,  Two  cuneiform, 

Two  arytenoid,  Epiglottis. 

The  thyroid  (^p«6? — doos,  like  a  shield)  is  the  largest  cartilage 
of  the  larynx  :  it  consists  of  two  lateral  portions,  or  alee,  which 
meet  at  an  angle  in  front,  and  form  the  projection  which  is  known 
by  the  name  of  pomum  Adami.  In  the  male,  after  puberty,  the 
angle  of  union  of  the  two  alae  is  acute ;  in  the  female,  and  before 


THE   LARYNX. 


289 


puberty  in  the  male,  it  is  obtuse.     Where  the  pomum  Adami  is 
prominent,  a  bursa  mucosa  is  often  found  between  it  and  the  skin. 

Each  ala  is  quadrilateral  in  shape, 
and  forms  a  rounded  border  posteri-  Fig.  92. 

orly,  which  terminates  above,  in  the 
superior  cornu  and  below,  in  the  in- 
ferior cornu.  Upon  the  side  of  the 
ala  is  an  oblique  line,  or  ridge,  directed 
downwards  and  forwards,  and  bounded 
at  each  extremity  by  a  tubercle.  Into 
this  line  the  sterno-thyroid  muscle  is 
inserted  ;  and  from  it  the  thyro-hyoid 
and  inferior  constrictor  take  their  ori- 
gin. In  the  receding  angle,  formed  by 
the  meeting  of  the  two  alae  upon  the 
inner  side  of  the  cartilage,  and  near  its 
lower  border,  are  attached  the  epi- 
glottis, the  chordae  vocales,  the  thyro- 
arytenoid,  and  thyro-epiglottidean 
muscles. 

The  cricoid  (xpt'xoj — tlBos,  like  a 
ring)  is  a  ring  of  cartilage,  narrow  in 
front,  and  broad  behind,  where  it  is 
surmounted  by  two  rounded  surfaces, 
which  articulate  with  the  arytenoid  ^01^—1^0  4*\h  "?<?  car* 
cartilages.  At  the  middle  line,  pos-  {jjjp^  j.  Vertical  ^idge^or 
teriorly,  is  a  vertical  ridge,  which  gives  pomum  Adami.  2.  Right  ala. 
attachment  to  the  oesophagus,  and  on  3-  Superior,  and  4,  inferior 
each  side  of  the  ridge  are  the  depres-  cricoid  cartiSge.*  ^T*  ' 
sions  which  lodge  the  crico-arytenoidei  arytenoid  cartilage, 
postici  muscles.  On  either  side  of  the 
ring  is  a  glenoid  cavity,  which  articulates  with  the  inferior  cornu 
of  the  thyroid  cartilage. 

The  arytenoid  cartilages  (apvi-otVa,1  a  pitcher),  two  in  number, 
are  triangular  and  prismoid  in  form.  They  are  broad  and  thick 
below,  where  they  articulate  with  the  upper  border  of  the  cricoid 
cartilage  ;  pointed  above,  and  prolonged  by  two  small  pyriform 
fibre-cartilages,  cornicula  laryngis  (capitula  Santoriui),  which 
are  curved  inwards  and  backwards ;  and  they  each  present  three 
surfaces,  anterior,  posterior,  and  internal.  The  posterior  surface 

1  This  derivation  has  reference  to  the  appearance  of  both  cartilages 
taken  together  and  covered  by  mucous  membrane.  In  animals,  which 
were  the  principal  subjects  of  dissection  among  the  ancients,  the  opening 
of  the  larynx  with  the  arytenoid  cartilages  bears  a  striking  resemblance 
to  the  mouth  of  a  pitcher  having  a  large  spout. 
25 


CARTILAGES  OF  THE  LARYNX 


290  THE   DISSECTOR. 

is  concave,  and  lodges  part  of  the  arytenoideus  muscle  ;  the  in- 
ternal surface  is  smooth,  and  forms  part  of  the  lateral  wall  of  the 
larynx ;  the  anterior  or  external  surface  is  rough  and  irregular, 
and  gives  attachment  to  the  chorda  vocalis,  thyro-arytenoideus, 
crico-arytenoideus  lateralis  and  posticus,  and,  above  these,  to  the 
base  of  the  cuneiform  cartilage. 

The  cuneiform  cartilages  are  two  small  cylinders  of  yellow 
fibre-cartilage,  about  seven  lines  in  length,  arid  enlarged  at  each 
extremity.  By  the  lower  end,  or  base,  the  cartilage  is  attached 
to  the  middle  of  the  external  surface  of  the  arytenoid ;  and,  by 
its  upper  extremity,  forms  a  prominence  in  the  border  of  the 
aryteno-epiglottidean  fold  of  membrane.  They  are  sometimes 
wanting. 

In  the  male,  the  cartilages  of  the  larynx  are  more  or  less  ossified, 
particularly  in  old  age. 

The  epiglottis  (ertiymfti$,  upon  the  tongue)  is  a  fibro -cartilage 
of  a  yellowish  color,  studded  with  a  number  of  small  mucous 
glands,  which  are  lodged  in  shallow  pits  upon  its  surface.  It  is 
shaped  like  a  cordate  leaf,  and  is  placed  immediately  in  front  of 
the  opening  of  the  larynx,  which  it  closes  completely  when  the 
larynx  is  drawn  up  beneath  the  base  of  the  tongue.  It  is  attached 
by  its  point  to  the  receding  angle  between  the  two  ala3  of  the 
thyroid  cartilage. 

Ligaments. — The  ligaments  of  the  larynx  are  numerous,  and 
may  be  arranged  into  four  groups :  1.  Those  which  articulate 
the  thyroid  with  the  os  hyoides.  2.  Those  which  connect  it  with 
the  cricoid.  3.  Ligaments  of  the  arytenoid  cartilages.  4.  Lig- 
aments of  the  epiglottis. 

1.  The  ligaments  which  connect  the  thyroid  cartilage  with  the 
os  hyoides  are  three  in  number. 

The  two  thyro-hyoidean  ligaments  pass  between  the  superior 
cornua  of  the  thyroid,  and  the  extremities  of  the  greater  cornua 
of  the  os  hyoides  :  a  sesamoid  bone  or  cartilage  is  found  in  each. 

The  thyro-hyoidean  membrane  is  a  broad  membranous  layer, 
occupying  the  entire  space  between  the  upper  border  of  the  thy- 
roid cartilage  and  the  upper  border  of  the  os  hyoides.  It  is 
pierced  by  the  superior  laryngeal  nerve  and  artery. 

2.  The  ligaments  connecting  the  thyroid  to  the  cricoid  carti- 
lage are  also  three  in  number — 

Two  capsular  ligaments,  with  their  synovial  membranes,  which 
form  the  articulation  between  the  inferior  cornua  of  the  thyroid 
and  the  sides  of  the  cricoid ;  and  the  crico-thyroidean  membrane. 
The  crico-thyroidean  membrane  is  a  fan-shaped  layer  of  yellow 
elastic  tissue,  thick  in  front  (middle  crico-thyroidean  ligament), 
and  thinner  at  each  side  (lateral  crico-thyroidean  ligament). 
It  is  attached  by  its  apex  to  the  lower  border  and  receding 


THE  LARYNX. 


291 


anodic  of  the  thyroid  cartilage,  and  by  its  expanded  margin  to  the 
upper  border  of  the  cricoid  and  base  of  the  arytenoid  cartilages. 
Superiorly  it  is  continuous  with  the  inferior  margin  of  the  chorda 
vocalis.  The  front  of  the  crico-thyroidean  membrane  is  crossed 
by  a  small  artery,  the  inferior  laryngeal,  and  is  the  spot  selected 
for  the  operation  of  laryngotomy.  Laterally  it  is  covered  in  by 
the  crico-thyroidei  and  crico-arytenoidei  laterales  muscles. 

3.  The  ligaments  of  the  arytenoid  cartilages  are  eight  in 
number — 

Two  capsular  ligaments,  with  synovial  membranes,  which  arti- 
culate the  arytenoid  cartilages  with  the  cricoid,  strengthened  be- 
hind by  two  posterior  crico-arytenoid  bands,  or  ligaments;  and 
the  superior  and  inferior  thy ro- arytenoid  ligaments.  The  supe- 
rior thyro-arytenoid  ligaments  are  two  thin  bands  of  yellow  elastic 
tissue,  which  are  attached  in  front  to  the  receding  angle  of  the 
thyroid  cartilage,  and  behind  to  the  anterior  and  inner  border  of 
each  arytenoid  cartilage.  The  lower  border  of  this  ligament 


Fig.  93. 


Fig.  94. 


A  POSTERIOUVIEW  OF  THE  LARYNX. 

— 1.  The  thyroid  cartilage.  2.  One 
of  its  ascending  cornua.  3.  One  of 
the  descending  cornua.  4,  7.  The 
cricoid  cartilage.  5,  5.  The  aryte- 
noideus  cartilages.  6.  The  arytenoi- 
deus  muscle,  consisting  of  oblique  and 
transverse  fasciculi.  7.  The  crico- 
arytenoid  postici  muscles.  8.  The 
epiglottis. 


A  SIDE  VIEW  OF  THE  LARYNX  :  ONE 
ALA  OF  THE  THYROID  CARTILAGE  HAS 
BEEN  REMOVED. — 1.  The  remaining 
ala  of  the  thyroid  cartilage.  2.  One 
of  the  arytenoid  cartilages.  3.  One 
of  the  cornicula  laryngis.  4.  The 
cricoid  cartilage.  5.  The  crico-ary- 
tenoideus  posticus  muscle.  6.  The 
crico-arytenoideus  lateralis.  7.  The 
thyro-arytenoideus.  8.  The  crico- 
thyroidean  membrane.  9.  One-half 
of  the  epiglottis.  10.  The  upper  part 
of  the  trachea. 


constitutes  the  upper  boundary  of  the  ventricle  of  the  larynx, 
and  the  fold  of  mucous  membrane  caused  by  its  projection  has 
been  called  the  superior  or  false  chorda  vocalis.  The  inferior 


292  THE   DISSECTOR. 

thyro-arytenoid  ligaments,  or  true  chordae  vocales,  are  thicker  than 
the  superior,  and,  like  them,  composed  of  yellow  elastic  tissue. 
Each  ligament  is  attached  in  front  to  the  receding  angle  of  the 
thyroid  cartilage,  and  behind  to  the  anterior  angle  of  the  base  of 
the  arytenoid.  The  inferior  border  of  the  chorda  vocalis  is  con- 
tinuous with  the  lateral  expansion  of  the  crico-thyroid  ligament. 
The  superior  border  forms  the  lower  boundary  of  the  ventricle 
of  the  larynx.  The  space  between  the  two  chordae  vocales  is  the 
glottis,  or  rima  glottidis. 

4.  The  ligaments  of  the  epiglottis  are  five  in  number, 
namely — three  glosso-epiglottic,  hyo-epiglottic,  and  thyro-epi- 
glottic. 

The  glosso-epiglottic  ligaments  (fraena  epiglottidis)  are  three 
folds  of  mucous  membrane,  which  connect  the  anterior  surface  of 
the  epiglottis  with  the  root  of  the  tongue.  The  middle  of  these 
contains  elastic  tissue.  The  hyo-epiglottic  ligament  is  a  band  of 
yellow  elastic  tissue,  passing  between  the  anterior  aspect  of  the 
epiglottis  near  its  apex,  and  the  upper  margin  of  the  body  of 
the  os  hyoides.  The  thyro-epiglottic  ligament  is  a  long  and  slen- 
der fasciculus  of  yellow  elastic  tissue,  which  embraces  the  apex 
of  the  epiglottis,  and  is  inserted  into  the  receding  angle  of  the 
thyroid  cartilage,  immediately  below  the  anterior  fissure,  and 
above  the  attachment  of  the  chords  vocales. 

Muscles. — The  muscles  of  the  larynx  are  eight  in  number :  the 
five  larger  are  the  muscles  of  the  chordae  vocales  and  rima  glot- 
tidis ;  the  three  smaller  are  muscles  of  the  epiglottis. 

The  five  muscles  of  the  chordae  vocales  and  rima  glottidis  are 
the— 

Crico-thyroid,  Thyro-arytenoideus, 

Crico-arytenoideus  posticus,  Arytenoideus. 

Crico-arytenoideus  lateralis, 

The  crico-thyroid  muscle  arises  from  the  anterior  surface  of 
the  cricoid  cartilage,  and  passes  obliquely  outwards  and  back- 
wards, to  be  inserted  into  the  lower  and  inner  border  of  the  ala 
of  the  thyroid,  from  its  tubercle 'as  far  back  as  the  inferior 
cornu. 

The  crico-arytenoideus  posticus  arises  from  the  depression  on 
the  posterior  surface  of  the  cricoid  cartilage,  and  passes  upwards 
and  outwards,  to  be  inserted  into  the  outer  angle  of  the  base  of 
the  arytenoid. 

The  crico-arytenoideus  lateralis  arises  from  the  upper  border 
of  the  side  of  the  cricoid,  and  passes  upwards  and  backwards, 
to  be  inserted  into  the  outer  angle  of  the  base  of  the  arytenoid 
cartilage. 

The  thyro-arytenoideus  arises  from  the  receding  angle  of  the 


THE   LARYNX.  293 

thyroid  cartilage,  close  to  the  outer  side  of  the  chorda  vocalis, 
and  passes  backwards,  parallel  with  the  cord,  to  be  inserted 
into  the  base  and  outer  surface  of  the  arytenoid  cartilage. 

The  arytenoideus  muscle  occupies  the  posterior  concave  surface 
of  the  arytenoid  cartilages,  between  which  it  is  stretched.  It 
consists  of  three  planes  of  transverse  and  oblique  fibres  ;  hence 
it  was  formerly  considered  as  several  muscles,  under  the  names  of 
transversi  and  olliqui. 

The  three  muscles  of  the  epiglottis  are  the — 
Thyro-epiglottideus, 
Aryteuo-epiglottideus  superior, 
Aryteno-epiglottideus  inferior. 

The  thyro-epiglottideus  appears  to  be  formed  by  the  upper 
fibres  of  the  thyro-arytenoideus  muscle ;  they  spread  out  upon  the 
external  surface  of  the  sacculns  laryngis,  and  in  the  aryteno-epi- 
glottidean  fold  of  mucous  membrane,  on  which  they  are  lost ;  a 
few  of  the  anterior  fibres  being  continued  onwards  to  the  side  of 
the  epiglottis  (depressor  epiglottidis). 

The  aryteno-epiglottideus  superior  consists  of  a  few  scattered 
fibres,  which  pass  forwards  in  the  fold  of  mucous  membrane, 
forming  the  lateral  boundary  of  the  entrance  into  the  larynx, 
from  the  apex  of  the  arytenoid  cartilage  to  the  side  of  the  epi- 
glottis. 

The  aryteno-epiglottideus  inferior. — This  muscle,  described  by 
Mr.  Hilton,  and  closely  connected  with  the  sacculus  laryngis, 
may  be  found  by  raising  the  mucous  membrane  immediately 
above  the  ventricle  of  the  larynx.  It  arises,  by  a  narrow  and 
fibrous  origin,  from  the  arytenoid  cartilage,  just  above  the  at- 
tachment of  the  chorda  vocalis  ;  and,  passing  forwards,  and  a 
little  upwards,  expands  over  the  upper  half,  or  two-thirds  of  the 
sacculus  laryngis,  and  is  inserted  by  a  broad  attachment  into  the 
side  of  the  epiglottis. 

ACTIONS. — From  a  careful  examination  of  the  muscles  of  the 
larynx,  Mr.  Bishop1  concludes,  that  the  crico-arytenoidei  postici 
open  the  glottis,  while  all  the  rest  close  it.  The  arytenoideus  ap- 
proximates the  arytenoid  cartilages  posteriorly,  and  the  crico- 
arytenoidei  laterales  and  thyro-arytenoidei  anteriorly;  the  latter, 
moreover,  close  the  glottis  mesially.  The  crico-thyroidei  are 
tensors  of  the  chordae  vocales,  and  these  muscles,  together  with 
the  thyro-arytenoidei,  regulate  the  tension,  position,  and  vibrat- 
ing length  of  the  vocal  cords. 

The  crico-thyroid  muscles  effect  the  tension  of  the  chords  vocales 

1  Cyclopaedia  of  Anatomy  and  Physiology,  art.  LARYNX. 
25* 


294 


THE   DISSECTOR. 


Fig.  95. 


by  rotating  the  cricoid  on  the  inferior  cornua  of  the  thyroid ;  by 

this  action,  the  anterior  portion  is 
drawn  upwards,  and  made  to  ap- 
proximate the  inferior  border  of 
the  thyroid,  while  the  posterior 
and  superior  border  of  the  cricoid, 
together  with  the  arytenoid  car- 
tilages, is  carried  backwards.  The 
cryco-arytenoidei  postici  separate 
the  chordae  vocales,  by  drawing 
the  outer  angles  of  the  arytenoid 
cartilages  outwards  and  down- 
wards. The  crico-arytenoidei  la- 
terales,  by  drawing  the  outer  angles 
of  the  arytenoid  cartilages  for- 
wards, approximate  the  anterior 
A  DIAGRAM,  SLIGHTLY  ALTERED  angles,  to  which  the  chordse  VO- 

LARYNXE—  l°F0PIn?ng  of  the  gfcifc  arytenoidei  draw  the  arytenoid  car- 
tis.  2, 2.  Arytenoid  cartilages.  3,  tilages  forwards,  and,  by  their 

3.  Vocal  cords.  4,  4.  Posterior  crico-  connection  with  the  chordae  VO- 
crLe-aryte™oS  muscle  ;  that  of  The  CaleS,  act  upon  the  whole  length 
left  side  is  removed.  6.  Arytenoid  of  those  COrds. 


side  is  removed.  8. 'uppeTborder  principally  by  compressing  the 
of  the  thyroid  cartilage.  9,  9.  glands  of  the  sacculus  laryngis, 

Upper  border  and  back  of  the  cri-  d  th  gac  jtgelf .  b  jtg  attach- 
com  cartilage.  13.  Posterior  crico-  .,  .  ,  /.  .,  ,-, 

arytenoid  ligament.  merit    to    the    epiglottis,    it    Would 

act  feebly  upon  that  valve.     The 

aryteno-epiglottideus  superior  serves  to  keep  the  mucous  mem- 
brane of  the  sides  of  the  opening  of  the  glottis  tense,  when  the 
larynx  is  drawn  upwards,  and  the  opening  closed  by  the  epiglot- 
tis. Of  the  aryteno-epiglottideus,  the  "functions  appear  to  be," 
writes  Mr.  Hilton,  "  to  compress  the  subjacent  glands  which 
open  the  pouch ;  to  diminish  the  capacity  of  that  cavity,  and 
change  its  form  ;  and  to  approximate  the  epiglottis  and  the  ary- 
tenoid cartilage." 

Mucous  Membrane. — The  aperture  of  the  larynx  is  a  triangular 
or  cordiform  opening,  broad  in  front  and  narrow  behind ;  bounded 
anteriorly  by  the  epiglottis,  posteriorly  by  the  arytenoideus 
muscle,  and  on  either  side  by  a  fold  of  mucous  membrane 
stretched  between  the  side  of  the  epiglottis  and  the  apex  of  the 
arytenoid  cartilage.  On  the  margin  of  this  aryteno-epiglottidean 
fold  the  cuneiform  cartilage  forms  a  prominence  more  or  less  dis- 
tinct. The  cavity  of  the  larynx  is  divided  into  two  parts  by  an 
oblong  constriction,  produced  by  the  prominence  of  the  chordae 


THE   LARYNX.  295 

vocales.  That  portion  of  the  cavity  which  lies  above  the  con- 
striction is  broad  and  triangular  above,  and  narrow  below ;  that 
which  is  below  it,  is  narrow  above  and  broad  and  cylindrical 
below,  the  circumference  of  the  cylinder  corresponding  with  the 
ring  of  the  cricoid  ;  while  the  space  included  by  the  constriction 
is  a  narrow,  triangular  fissure,  the  glottis,  or  rima  glottidis.  The 
form  of  the  glottis  is  that  of  an  isosceles  triangle,  bounded  on 
the  sides  by  the  chordae  vocales  and  inner  surface  of  the  aryte- 
noid  cartilages,  and  behind  by  the  aryteuoideus  muscle.  Its 
length  is  greater  in  the  male  than  in  the  female ;  and,  in  the 
former,  measures  somewhat  less  than  an  inch.  Immediately  above 
the  prominence  caused  by  the  chorda  vocalis,  and  extending 
nearly  its  entire  length  on  each  side  of  the  cavity  of  the  larynx, 
is  an  elliptical  fossa,  the  ventricle  of  the  larynx.  This  fossa  is 
bounded  below  by  the  chorda  vocalis,  which  it  serves  to  isolate ; 
and  above,  by  a  border  of  mucous  membrane  folded  upon  the 
lower  edge  of  the  superior  thyro-arytenoid  ligament  (superior  or 
false  chorda  vocalis).  The  whole  of  the  cavity  of  the  larynx, 
with  its  prominences  and  depressions,  is  lined  by  mucous  mem- 
brane, which  is  continuous,  superiorly,  with  that  of  the  mouth 
and  pharynx ;  and  inferiorly,  is  prolonged  through  the  trachea 
and  bronchial  tubes  into  the  lungs.  In  the  ventricles  of  the 
larynx  the  mucous  membrane  forms  a  caecal  pouch  of  variable 
size,  termed  by  Mr.  Hilton  the  sacculus  laryngis*  The  sacculus 
laryngis  is  directed  upwards,  sometimes  extending  as  high  as  the 
upper  border  of  the  thyroid  cartilage,  and  occasionally  above  that 
border.  When  dissected  from  the  interior  of  the  larynx,  it  is 

1  This  sac  was  described  by  Mr.  Hilton  before  he  was  aware  that  it 
had  already  been  pointed  out  by  the  older  anatomists.  I  myself  made  a 
dissection,  which  I  still  possess,  of  the  same  sac  in  an  enlarged  state, 
during  the  month  of  August,  1837,  without  any  knowledge  either  of  Mr. 
Hilton's  labors  or  Morgagni's  account.  The  sac  projected  considerably 
above  the  upper  border  of  the  thyroid  cartilage,  and  the  extremity  had 
been  snipped  off  on  one  side  in  the  removal  of  the  muscles.  The  larynx  was 
presented  to  me  by  Dr.  George  Moore,  of  Camberwell ;  he  had  obtained  it 
from  a  child  who  died  of  bronchial  disease  ;  and  he  conceived  that  this 
peculiar  disposition  of  the  mucous  membrane  might  possibly  explain 
some  of  the  symptoms  by  which  the  case  was  accompanied.  Cruveilhier 
made  the  same  observation  in  equal  ignorance  of  Morgagni's  description, 
for  we  read  in  a  note  at  p.  677,  vol.  ii.  of  his  Anatomie  Descriptive: 
"  J'ai  vu  pour  la  premiere  fois  cette  arriere  cavite  chez  un  individu  affect^ 
de  phthisie  laryngee,  ou  elle  etait  tres-developpee.  Je  fis  des  recherches 
sur  le  larynx  d'autres  individus,  et  je  trouvai  que  cette  disposition  6tait 
constante.  Je  ne  savais  pas  alors  que  Morgagni  avait  indique  et  fait 
representer  la  meme  disposition."  Cruveilhier  compares  its  form  very 
aptly  to  a  " Phrygian  casque"  and  Morgagni's  figure,  Advers.  1,  Epist. 
Auat.  3,  plate  2,  fig.  4,  has  the  same  appearance.  But  neither  of  these 
anatomists  notice  the  follicular  glands  described  by  Mr.  Hilton. 


296  THE   DISSECTOR. 

found  covered  by  the  aryteno-epiglottideus  muscle  and  a  fibrous 
membrane,  which  latter  is  attached  to  the  superior  thyro-aryte- 
noid  ligament  below  ;  to  the  epiglottis  in  front ;  and  to  the  upper 
border  of  the  thyroid  cartilage  above.  If  examined  from  the 
exterior  of  the  larynx,  it  will  be  seen  to  be  covered  by  the  thyro- 
epiglottideus  muscle.  On  the  surface  of  its  mucous  membrane 
are  the  openings  of  sixty  or  seventy  small  follicular  glands,  which 
are  situated  in  the  sub-mucous  tissue,  and  give  to  its  external 
surface  a  rough  and  ill-dissected  appearance.  The  secretion 
from  these  glands  is  intended  for  the  lubrication  of  the  chordae 
vocales,  and  is  directed  upon  them  by  two  small  valvular  folds 
of  mucous  membrane,  which  are  situated  at  the  entrance  of  the 
sacculus.  The  mucous  membrane  is  closely  connected  to  the 
epiglottis,  and  to  the  chords  vocales  ;  on  the  latter,  being  re- 
markable for  its  thinness.  It  is  invested  by  a  columnar  ciliated 
epithelium  as  high  up  as  the  superior  folds  of  the  ventricle  of  the 
larynx  and  the  lower  half  of  the  epiglottis. 

Glands. — The  mucous  membrane  of  the  larynx  is  furnished 
with  an  abundance  of  mucous  glands  ;  many  of  these  are  situated 
on  the  epiglottis,  in  the  sacculus  laryngis,  and  in  the  aryteno- 
epiglottidean  folds,  where  they  are  termed  arytenoid.  The  body 
known  as  the  epiglottic  gland  is  merely  a  mass  of  cellular  and 
adipose  tissue,  situated  in  the  triangular  space  between  the  front 
surface  of  the  apex  of  the  epiglottis,  the  hyo-epiglottidean  liga- 
ment, and  the  thyro-hyoidean  membrane. 

Vessels  and  Nerves. — The  arteries  of  the  larynx  are  derived 
from  the  superior  and  inferior  thyroid.  The  nerves  are  the  supe- 
rior laryngeal  and  recurrent  laryngeal,  both  branches  of  the 
pneumogastric.  The  two  nerves  communicate  with  each  other 
freely,  but  the  superior  laryngeal  is  distributed  principally  to  the 
mucous  membrane  at  the  entrance  of  the  larynx ;  the  recurrent 
to  the  muscles. 

TRACHEA. — The  trachea  or  windpipe  is  cylindrical  for  about 
two-thirds  of  its  circumference,  and  flattened  on  the  posterior 
third,  where  it  rests  on  the  oesophagus.  It  is  about  four  inches 
in  length,  and  extends  from  opposite  the  fifth  cervical  vertebra  to 
opposite  the  third  dorsal  vertebra,  where  it  divides  into  two 
bronchi.  Its  area  is  somewhat  larger  in  the  male  than  in  the 
female,  and  its  diameter  from  side  to  side  about  an  inch. 

It  is  composed  of  fibro-cartilaginous  rings,  fibrous  membrane, 
muscular  fibres,  fibres  of  elastic  fibrous  tissue,  and  is  lined  by 
mucous  membrane. 

The  fibro-cartilaginous  rings  are  from  fifteen  to  twenty  in 
number,  and  extend  for  two-thirds  around  its  cylinder,  being 
deficient  at  the  posterior  part.  The  first  ring  is  received  within 
the  lower  margin  of  the  cricoid  cartilage,  and  is  broader  than  the 


ORGAN    OP   TOUCH.  297 

rest ;  the  last  is  broad  at  the  middle  in  consequence  of  the  pro- 
longation of  the  lower  border  into  a  triangular  process  which 
curves  backwards  at  the  point  of  bifurcation.  The  posterior  ex- 
tremities of  the  rings  are  rounded,  and  occasionally  one  or  two 
rings  will  be  found  to  bifurcate. 

The  fibrous  membrane  connects  the  rings  and  forms  a  thin 
covering  to  them  on  the  outer  surface.  Internally  it  does  not 
reach  the  surface,  and  the  rings  have  in  consequence  an  appear- 
ance of  greater  prominence.  It  also  stretches  across  between 
the  rings  on  the  posterior  part  of  the  trachea. 

The  muscular  fibres  are  disposed  transversely  across  the  space, 
between  the  extremities  of  the  fibro-cartilages  behind.  They  are 
placed  internally  to  the  fibrous  membrane. 

The  elastic  fibrous  tissue  is  disposed  in  longitudinal  bundles, 
within  the  fibro-cartilages  ;  and,  behind,  internally  to  the  mus- 
cular layer. 

The  mucous  membrane,  which  is  pale,  forms  the  internal  lining 
of  the  tube,  and  has  opening  upon  its  surface  the  excretory  tubes 
of  numerous  mucous  glands.  These  glands  are  situated  for  the 
most  part  between  the  layers  of  membrane  in  the  back  part  of  the 
tube. 

ORGAN  OP  TOUCH. 

The  skin  is  the  exterior  investment  of  the  body,  which  it  serves 
to  cover  and  protect.  It  is  continuous  at  the  apertures  of  the 
internal  cavities,  with  the  lining  membrane  of  those  cavities,  the 
internal  skin,  or  mucous  membrane,  and  is  composed  essentially  of 
two  layers,  derma  and  epiderma. 

The  DERMA,  or  cutis,  is  chiefly  composed  of  cellulo-fibrous 
tissue,  besides  which  it  has  entering  into  its  structure  elastic  and 
contractile  fibrous  tissue,  together  with  bloodvessels,  lymphatic 
vessels,  and  nerves.  The  cellulo-fibrous  tissue  exists  in  greatest 
abundance  in  the  deeper  stratum  of  the  derma,  which  is  conse- 
quently dense,  white,  and  coarse ;  the  superficial  stratum,  on  the 
other  hand,  is  fine  in  texture,  reddish  in  color,  soft,  raised  into 
minute  papillae,  and  highly  vascular  and  sensitive.  These  differ- 
ences in  structure  have  given  rise  to  a  division  of  the  derma  into 
the  deep  stratum,  or  corium,  and  the  superficial,  or  papillary 
layer. 

In  the  corium  the  cellulo-fibrous  tissue  is  collected  into  fasci- 
culi, which  are  small  and  closely  interwoven  in  the  superficial 
strata,  large  and  coarse  in  the  deep  strata ;  in  the  latter  form- 
ing an  areolar  network  with  large  areolae,  which  are  occupied  by 
adipose  tissue.  These  areola?  are  the  channels  by  which  the 
branches  of  vessels  and  nerves  find  a  safe  passage  to  the  papillary 
layer,  in  which  and  in  the  superficial  strata  of  the  corium  they  are 


298  THE   DISSECTOR. 

principally  distributed.  The  yellow  elastic  tissue  is  found  chiefly 
in  the  superficial  strata,  the  red  contractile  tissue  in  the  deep.  It 
is  to  the  latter  that  the  nipples  and  scrotum  owe  their  contractile 
powers,  and  the  general  surface  of  the  skin  the  contraction  which 
is  known  by  the  name  of  cutis  anserina.  The  corium  present 
some  variety  in  thickness  in  different  parts  of  the  body.  Thus  in 
the  more  exposed  regions,  as  the  back,  the  outer  sides  of  the 
limbs,  the  palms,  and  the  soles,  it  is  remarkable  for  its  thickness  ; 
while  on  protected  parts  it  is  comparatively  thin.  On  the  eyelids, 
the  penis,  and  the  scrotum  it  is  peculiarly  delicate.  It  is  con- 
nected by  its  under  surface  with  the  common  superficial  fascia 
of  the  body. 

The  papillary  layer  of  the  derma  is  raised  in  the  form  of 
conical  prominences  or  papillae.  On  the  general  surface  of  the 
body  the  papillaa  are  short  and  exceedingly  minute  ;  but  in  other 

Fig.  96. 


A  SECTION  OF  THE  SKIN.  —  1.  The  corium.  2.  The  papillary  layer  of  the 
cutis.  3.  The  rete  mucosum  modelled  upon  the  papillae.  4.  The  cuticle.  5. 
Spiral  sweat  ducts,  opening  at  the  pores  upon  the  ridges  of  the  cuticle. 

situations,  as  the  palmar  surface  of  the  hands  and  fingers,  and 
the  plantar  surface  of  the  feet  and  toes,  they  are  long  and  of 
large  size.  They  also  differ  in  arrangement  ;  for,  on  the  general 
surface,  they  are  distributed  at  unequal  distances  and  without 
order;  whereas,  on  the  palms  and  soles,  and  on  the  correspond- 
ing surfaces  of  the  fingers  and  toes,  they  are  collected  into  little 
square  clumps,  containing  from  ten  to  twenty  papillaa;  and  these 
little  clumps  are  disposed  in  parallel  rows.  It  is  this  arrange- 
ment in  rows  that  gives  rise  to  the  characteristic  parallel  ridges 
and  furrows  which  are  met  with  on  the  hands  and  feet.  The  pa- 
pilla3  in  these  little  square  clumps  are  for  the  most  part  uniform 
in  size  and  length,  but  every  here  and  there  one  papilla  may  be 
observed  which  is  longer  than  the  rest.  The  largest  papillae  of 
the  derma  are  those  which  produce  the  nail  ;  in  the  dermal  follicle 
of  the  nail  they  are  long  and  filiform,  while  beneath  its  concave 
surface  they  form  longitudinal  and  parallel  plications  which  ex- 
tend for  nearly  the  entire  length  of  that  organ.  In  structure  each 
papilla  is  composed  of  a  more  or  less  convoluted  capillary  and  a 
more  or  less  convoluted  nervous  loop. 


EPIDERMA.  299 

The  EPIDERMA  or  cuticle  (scarf  skin),  is  a  product  of  the  derma, 
which  it  serves  to  envelop  and  defend.  That  surface  of  the 
epiderma  which  is  exposed  to  the  influence  of  the  atmosphere 
and  exterior  sources  of  injury  is  hard  and  horny  in  texture,  while 
that  which  lies  in  contact  with  the  papillary  layer  is  soft  and  cel- 
lular. Hence  the  epiderma,  like  the  derma,  is  divisible  into  two 
layers,  external  and  internal,  the  latter  being  termed  the  rete 
mucosum.  Moreover,  the  epiderma  is  laminated  in  structure, 
and  the  laminae  present  a  progressively  increasing  tenuity  and 
density  as  they  advance  from  the  inner  to  the  outer  surface.  This 
difference  of  density  is  dependent  on  the  mode  of  growth  of  the 
epiderma,  for  as  the  external  surface  is  constantly  subjected  to 
destruction  from  attrition  and  chemical  action,  so  the  membrane 
is  continually  reproduced  on  its  internal  surface  ;  new  layers 
being  successively  formed  on  the  derma  to  take  the  place  of 
the  old. 

The  theory  of  growth  of  the  epiderma,  deduced  from  the  ob- 
servations of  Schwann,  is  as  follows  :  A  stratum  of  plastic 
lymph  (liquor  sanguinis)  is  poured  out  upon  the  surface  of  the 
derma.  This  fluid,  by  virtue  of  the  vital  force  inherent  in  itself, 
and  communicated  to  it  by  contact  with  a  living  tissue,  is  con- 
verted into  granules,  which  are  termed  cell-germs,  or  cytollasts. 
By  endosmosis,  these  cytoblasts  imbibe  serum  from  the  plastic 
lymph  and  adjacent  tissues,  and  the  outermost  layer  or  pellicle 
of  the  cytoblast  becomes  gradually  distended  by  the  imbibed 
fluid.  The  cytoblast  has  now  become  a  cell,  and  the  solid  por- 
tion of  the  cytoblast,  which  always  remains  adherent  to  some 
one  point  of  the  internal  surface  of  the  cell-membrane,  is  the 
nucleus  of  the  cell.  Moreover,  within  the  nucleus,  one  or  several 
nuclei  are  formed,  which  are  termed  nucleoli.  By  a  continuance 
of  the  process  of  imbibition,  the  cell  becomes  more  or  less 
spherical ;  so  that,  after  a  time,  every  part  of  the  surface  of  the 
pupillary  layer  of  the  derma  is  coated  by  a  thin  and  membranous 
stratum,  consisting  of  spherical  cells  lying  closely  pressed  toge- 
ther, and  corresponding  with  every  irregularity  which  the  papill® 
] trcsent.  But,  as  this  production  of  cells  is  a  function  constantly 
in  operation,  a  new  layer  is  formed  before  the  first  is  completed, 
and  the  latter  is  separated  by  subsequent  formations  further  and 
further  from  the  surface  of  the  papillary  layer.  As  a  conse- 
quence of  loss  of  contact  with  the  derma,  the  vital  force  is  pro- 
gressively diminished  ;  the  cell  becomes  subject  to  the  influence 
of  physical  laws,  and  evaporation  of  its  fluid  slowly  ensues.  In 
consequence  of  this  evaporation  the  cell  becomes  collapsed  and 
flattened,  and  assumes  an  elliptical  form;  the  latter  is  by  degrees 
converted  into  the  flat  cell  with  parallel  and  contiguous  layers, 
and  an  included  nucleolated  nucleus ;  and,  lastly,  the  flattened 


300  THE   DISSECTOR. 

cell  desiccates  into  a  thin  membranous  scale,  in  which  the  nucleus 
is  no  longer  apparent. 

My  own  investigations1  have  shown  that,  after  the  original 
granules  of  the  liquor  sanguinis  have  become  aggregated  into 
a  granular  nucleus,  other  granules  are  formed  in  successive  cir- 
cles around  the  circumference  of  the  nucleus,  until  the  entire 
breadth  of  the  epidermal  scale  is  attained  ;  that  the  cell  never 
acquires  a  greater  thickness  than  that  of  the  original  nucleus  ; 
and  that  the  formation  of  the  scale  results  from  the  desiccation 
of  the  cell,  as  it  is  gradually  pushed  outwards  from  the  derma 
towards  the  surface.  Consequently,  the  cell  never  possesses  any 
other  than  the  flattened  form  ;  all  its  phases  of  growth  are  per- 
fected in  the  deepest  layer  of  the  epiderma ;  and,  in  its  internal 
structure,  it  is  a  parent  cell  containing  secondary  and  tertiary 
cells  and  granules,  its  growth  being  the  result  of  the  growth  of 
these  secondary  formations. 

The  under  surface  of  the  epiderma  is  accurately  modelled  on 
the  papillary  layer  of  the  derma,  each  papilla  having  its  appro- 
priate sheath  in  the  newly-formed  epiderma  or  rete  mucosurn,  and 
each  irregularity  of  surface  of  the  former  having  its  representa- 
tive in  the  soft  tissue  of  the  latter.  On  the  external  surface,  this 
character  is  lost;  the  minute  elevations  corresponding  with  the 
papillae  are,  as  it  were,  polished  down,  and  the  surface  is  rendered 
smooth  and  uniform.  The  palmar  and  plantar  surfaces  of  the  hands 
and  feet  are,  however,  an  exception  to  this  rule ;  for  here,  in  con- 
sequence of  the  large  size  of  the  papillae  and  their  peculiar  ar- 
rangement in  rows,  ridges  corresponding  with  the  papillae  are 
strongly  marked  on  the  superficial  surface  of  the  epiderma.  The 
epiderma  is  remarkable  for  its  thickness  in  situations  where  the 
papillae  are  large,  as  in  the  palms  and  soles.  In  other  situations, 
it  assumes  a  character  which  is  also  due  to  the  nature  of  the  sur- 
face of  the  derma ;  namely,  that  of  being  marked  by  a  network 
of  linear  furrows,  which  trace  out  the  surface  into  small  polygo- 
nal and  lozenge-shaped  areae.  These  lines  correspond  with  the 
folds  of  the  derma  produced  by  its  movements,  and  are  most  nu- 
merous where  those  movements  are  the  greatest,  as  in  the  flexures 
and  on  the  convexities  of  joints. 

The  dark  color  of  the  skin  among  the  natives  of  the  South  is 
due  to  the  coloration  of  the  primitive  granules  of  which  the  cell 
is  composed,  especially  the  nucleus.  As  the  cells  desiccate,  the 
color  of  the  granules  is  lost ;  hence  the  deeper  hue  of  the  rete 
mucosum. 

The  pores  of  the  epiderma  are  the  openings  of  the  perspiratory 
ducts,  hair  follicles,  and  sebaceous  glands. 

1  Diseases  of  the  Skin,  2d  edit.,  p.  5. 


THE   NAILS.  301 

Vessels  and  Nerves. — The  arteries  of  the  derma  which  enter 
its  structure  through  the  areolae  of  the  under  surface  of  the  coriura, 
divide  into  innumerable  intermediate  vessels,  which  form  a  rich 
capillary  plexus,  in  the  superficial  strata  of  the  skin,  and  in  its 
papillary  layer.  In  the  papillae  of  some  parts  of  the  derma,  as 
in  the  longitudinal  plications  beneath  the  nail,  the  capillary  ves- 
sels form  simple  loops,  but  in  other  papillae  they  are  convoluted 
to  a  greater  or  less  degree  in  proportion  to  the  size  and  import- 
ance of  the  papillae.  The  lymphatic  vessels  probably  form,  in  the 
superficial  strata  of  the  derma,  a  plexus,  the  meshes  of  which  are 
interwoven  with  those  of  the  capillary  and  nervous  plexus.  No 
lymphatics  have  as  yet  been  discovered  in  the  papillae. 

The  nerves  of  the  derma,  after  entering  the  areolae  of  the  deeper 
part  of  the  coriura,  divide  into  minute  fasciculi,  which  form  a  ter- 
minal plexus  in  the  upper  strata  of  the  corium.  From  this  plexus 
the  primitive  fibres  pass  off  to  their  distribution,  as  loops,  in  the 
papillae.  In  the  less  sensitive  parts  of  the  skin  the  loops  are 
simple  and  more  or  less  acute  in  their  bend,  in  conformity  with 
the  figure  of  the  papillae.  In  the  sensitive  parts,  however,  and 
especially  in  the  tactile  papillae  of  the  pulps  of  the  fingers,  the 
loop  is  convoluted  to  a  greater  or  less  extent,  and  acts  as  a  mul- 
tiplier of  sensation. 

APPENDAGES  OF  THE  SKIN. 

The  appendages  of  the  skin  are  the  nails,  hairs,  sebaceous 
glands,  and  perspiratory  glands  and  ducts. 

The  NAILS  are  horny  appendages  of  the  skin,  identical  in 
formation  with  the  epiderma,  of  which  they  are  u  part.  A  nail 
is  convex  on  its  external  surface,  concave  within,  and  implanted 
by  means  of  a  thin  margin  or  root  in  a  fold  of  the  derma,  which 
is  nearly  two  lines  in  depth,  and  acts  the  part  of  a  follicle  to  the 
nail.  At  the  bottom  of  the  groove  of  the  follicle  are  a  number 
of  filiform  papillae,  which  produce  the  margin  of  the  root,  and, 
by  the  successive  formation  of  new  cells,  push  the  nail  onwards 
in  its  growth.  The  concave  surface  of  the  nail  is  in  contact  with 
the  derma,  and  the  latter  is  covered  by  papillae,  which  perform 
the  double  office  of  retaining  the  nail  in  its  place,  and  giving  it 
increased  thickness  by  the  addition  of  newly-formed  cells  to  its 
under  surface.  It  is  this  constant  change  occurring  in  the  under 
surface  of  the  nail,  co-operating  with  the  continual  reproduction 
taking  place  along  the  margin  of  the  root,  which  insures  the 
growth  of  the  nail  in  the  proper  direction.  The  nail  derives  a 
peculiarity  of  appearance  from  the  disposition  and  form  of  the 
papilla;  on  the  lingual  surface  of  the  derma  (matrix).  Thus, 
beneath  the  root,  and  for  a  short  distance  onwards  towards  its 
26 


302  THE   DISSECTOR. 

middle,  the  derma  is  covered  by  papillae  which  are  more  minute, 
and  consequently  less  vascular  than  the  papillae  somewhat  further 
on.  This  patch  of  papilla?  is  bounded  by  a  semilunar  line,  and 
the  part  of  the  nail  covering  it  being  lighter  in  color  than  the 
rest,  has  been  termed  lunula.  Beyond  the  lunula  the  papillae  are 
raised  into  longitudinal  plaits,  which  are  exceedingly  vascular, 
and  give  a  deeper  tint  of  redness  to  the  nail.  These  plait-like 
papillae  of  the  derma  are  well  calculated  by  their  form  to  offer  an 
extensive  surface  both  for  the  adhesion  and  formation  of  the  nail. 
The  granules  and  cells  are  developed  on  every  part  of  their  sur- 
face, both  in  the  grooves  between  the  plaits  and  on  their  sides, 
and  a  horny  lamina  is  formed  between  each  pair  of  plaits.  When 
the  under  surface  of  a  nail  is  examined,  these  longitudinal  laminae, 
corresponding  with  the  longitudinal  papillae  of  the  ungual  portion 
of  the  derma,  are  distinctly  apparent,  and  if  the  nail  be  forcibly 
detached,  the  laminae  may  be  seen  in  the  act  of  parting  from  the 
grooves  of  the  papillae.  It  is  this  structure  that  gives  rise  to  the 
ribbed  appearance  of  the  nail.  The  papillary  surface  of  the 
derma  which  produces  the  nail  is  continuous  around  the  circum- 
ference of  the  attached  part  of  that  organ  with  the  derma  of  the 
surrounding  skin,  and  the  horny  structure  of  the  nail  is  conse- 
quently continuous  with  that  of  the  epiderma. 

HAIRS  are  horny  appendages  of  the  skin  produced  by  the  in- 
volution and  subsequent  evolution  of  the  epiderma ;  the  involution 
constituting  the  follicle  in  which  the  hair  is  inclosed,  and  the 
evolution  the  shaft  of  the  hair.  Hairs  vary  much  in  size  and 
length  in  different  parts  of  the  body ;  in  some  they  are  so  short 
as  not  to  appear  beyond  the  follicle ;  in  others  thSy  grow  to  a 
great  length,  as  on  the  scalp  ;  while  along  the  margins  of  the 
eyelids  and  in  the  whiskers  and  beard,  they  are  remarkable  for 
their  thickness.  Hairs  are  generally  more  or  less  flattened  in 
form,  and  when  the  extremity  of  a  transverse  section  is  examined, 
it  is  found  to  possess  an  elliptical  or  reniform  outline.  This  ex- 
amination also  demonstrates  that  the  centre  of  the  hair  is  porous 
and  loose  in  texture,  while  its  periphery  is  dense  ;  thus  affording 
ground  for  its  division  into  a  cortical  and  a  medullary  portion. 
The  free  extremity  of  a  hair  is  generally  pointed,  and  sometimes 
split  into  two  or  three  filaments.  Its  attached  extremity  is  im- 
planted deeply  in  the  integument  extending  through  the  derma 
into  the  subcutaneous  cellular  tissue,  where  it  is  surrounded  by 
adipose  cells.  The  central  extremity  of  a  hair  is  larger  than  its 
shaft,  and  is  called  the  root  or  bulb.  It  is  rounded  or  conical  in 
its  shape. 

The  process  of  formation  of  a  hair  by  its  follicle  is  identical 
with  that  of  the  formation  of  the  epiderma  by  the  papillary  layer 
of  the  derma.  Plastic  lymph  is  in  the  first  instance  exuded  by 


SEBACEOUS   GLANDS.  303 

the  capillary  plexns  of  the  follicle,  the  lymph  undergoes  conver- 
sion, first  into  granules,  then  into  cells,  and  the  latter  are  elongated 
into  fibres.  The  cells  which  are  destined  to  form  the  surface  of 
the  hair,  go  through  a  different  process.  They  are  converted 
into  flat  scales,  which  inclose  the  fibrous  structure  of  the  interior. 
These  scales,  as  they  are  successively  produced,  overlap  those 
which  precede  and  give  rise  to  the  prominent  and  waving  lines 
which  may  be  seen  around  the  circumference  of  a  hair.  It  is  this 
overlapping  line  that  is  the  cause  of  the  roughness  which  we 
experience  in  drawing  a  hair,  from  its  point  to  its  bulb,  between 
the  fingers.  The  bulb  is  the  newly-formed  portion  of  the  hair  : 
its  expanded  form  is  due  to  the  greater  bulk  of  the  fresh  cells 
compared  with  the  fibres  and  scales  into  which  they  are  subse- 
quently converted  in  the  shaft. 

The  color  of  the  hair,  like  that  of  the  epiderma,  is  due  to  the 
coloration  of  the  primitive  granules  of  the  cells. 

The  SEBACEOUS  GLANDS  are  sacculated  glandular  organs  em- 
bedded in  the  substance  of  the  derma,  and  presenting  every 
variety  of  complexity,  from  the  simplest  pouch-like  follicle  to  the 
sacculated  and  lobulated  gland.  In  some  situations,  the  excre- 
tory ducts  of  these  glands  open  independently  on  the  surface  of 
the  epiderma ;  while  in  others,  and  the  most  numerous,  they  ter- 
minate in  the  follicles  of  the  hairs.  The  sebaceous  glands  asso- 
ciated with  the  hairs  are  racemiform  and  lobulated  in  structure, 
consisting  of  sacculi  which  open  by  short  pedunculated  tubuli 
into  a  common  excretory  duct,  and  the  latter,  after  a  short  course, 
terminates  in  the  hair-follicle.  In  the  scalp  there  are  two  of 
these  glands  to  each  hair-follicle.  On  the  nose  and  face  the 
glands  are  of  large  size,  distinctly  lobulated,  and  constantly  asso- 
ciated with  small  hair-follicles.  In  the  meatus  auditorius  the 
sebaceous  (ceruminous)  glands  are  also  large  and  lobulated,  but 
the  largest  are  those  of  the  eyelids,  the  Meibomian  glands.  The 
excretory  ducts  of  sebaceous  glands  offer  some  diversity  in  dif- 
ferent parts  of  the  body ;  thus,  in  many  situations  they  are  short 
and  straight,  while  in  others,  as  in  the  palms  of  the  hands  and 
soles  of  the  feet,  where  the  epiderma  is  thick,  they  assume  a  spiral 
arrangement.  The  sebaceous  ducts  are  lined  by  an  inversion  of 
the  epiderma,  which  forms  a  thick  and  funnel-shaped  cone  at  its 
commencement,  but  soon  becomes  uniform  and  soft.  Sebaceous 
glands  are  met  with  in  all  parts  of  the  body,  but  are  most 
abundant  in  the  skin  of  the  face,  and  in  these  situations  which 
are  naturally  exposed  to  the  influence  of  friction. 

The  sebaceous  substance,  when  it  collects  in  inordinate  quan- 
tities within  the  excretory  ducts,  becomes  the  habitat  of  a  very 
remarkable  parasitic  animal,  the  steatozoon  folliculorum. 

The  SUDORIFEIIOUS  GLANDS  are  situated  deeply  in  the  corium 


304  THE   DISSECTOR. 

and  also  in  the  subcutaneous  cellular  tissue,  where  they  are  sur- 
rounded by  adipose  cells.  They  are  small,  oblong  bodies,  com- 
posed of  one  or  more  convoluted  tubuli,  or  of  a  congeries  of 
globular  sacs,  which  open  into  a  common  efferent  duct.  The 
latter  ascends  from  the  gland  through  the  derma  and  epiderma, 
and  terminates  on  the  surface  by  a  funnel-shaped  and  oblique 
aperture  or  pore.  The  efferent  duct  presents  some  variety  in  its 
course  upwards  :  thus  within  the  derma  it  is  curved  and  serpen- 
tine, and  if  the  epiderma  be  thin,  it  proceeds  more  or  less  directly 
to  the  excreting  pore.  Sometimes  it  is  spirally  curved  within 
the  derma,  and  having  passed  the  latter,  is  regularly  and  beauti- 
fully spiral  in  its  passage  through  the  epiderma,  the  last  turn 
forming  an  oblique  and  valvular  opening  on  the  surface.  The 
spiral  course  of  the  duct  is  especially  remarkable  in  the  thick 
epiderma  of  the  palm  of  the  hand  and  sole  of  the  foot.  On  those 
parts  of  the  skin  where  the  papillae  are  irregularly  distributed, 
the  efferent  ducts  of  the  sudoriferous  glands  open  on  the  surface 
also  irregularly,  while  on  the  palmar  and  plantar  surfaces  of  the 
hands  and  feet,  the  pores  are  situated  at  regular  distances  along 
the  ridges,  at  points  corresponding  with  the  intervals  of  the 
small,  square-shaped,  clumps  of  papillae.  Indeed  the  apertures 
of  the  pores,  seen  upon  the  surface  of  the  epidermal  ridges,  give 
rise  to  the  appearance  of  small  transverse  furrows,  which  inter- 
sect the  ridges  from  point  to  point. 

The  efferent  duct  and  the  component  sacs  and  tubuli  of  the 
sudoriferous  gland  are  lined  by  an  inflection  of  the  epiderma. 
This  inflection  is  thick  and  infundibuliform  in  the  upper  stratum 
of  the- derma,  but  soon  becomes  uniform  and  soft.  The  infundi- 
buliform projection  is  drawn  out  from  the  duct  when  the  epiderma 
is  removed,  and  may  be  perceived  on  the  under  surface  of  the 
latter  as  a  nipple-shaped  cone.  A  good  view  of  the  sudoriferous 
ducts  is  obtained  by  gently  separating  the  epiderma  of  a  portion 
of  decomposing  skin ;  or  they  may  be  better  seen  by  scalding  a 
piece  of  skin,  and  then  withdrawing  the  epiderma  from  the 
derma.  In  both  cases  it  is  the  lining  sheath  of  epiderma  which 
is  drawn  out  from  the  duct. 


THORAX.  305 


CHAPTER    VI. 

THORAX. 

THE  THORAX  is  the  conical  cavity  situated  at  the  upper  part  of 
the  trunk  of  the  body.  It  is  narrow  above  and  broad  below,  and 
is  bounded,  in  front,  by  the  sternum,  six  superior  intercostal  car- 
tilages, ribs,  and  intercostal  muscles ;  laterally,  by  the  ribs  and 
intercostal  muscles  ;  and  behind  by  the  ribs,  intercostal  muscles, 
and  vertebral  column,  as  low  down  as  the  upper  margin  of  the 
last  rib  and  first  lumbar  vertebra. 

To  examine  the  contents  of  the  thorax,  the  anterior  and  lateral  wall  of 
the  chest  must  be  removed.  This  dissection  is  effected  by  sawing  across 
the  sternum  immediately  below  the  articulation  of  the  first  ribs,  and 
again  immediately  above  the  articulation  of  the  cartilages  of  the  sixth 
ribs.  From  these  points  carry  the  knife  along  the  lower  edge  of  the  first 
rib  jtbove,  and  upper  edge  of  the  sixth  rib  below,  as  far  back  as  may  be 
convenient,  and  connect  the  ends  of  the  incisions  by  a  section  of  the  ribs 
and  intercostal  muscles,  from  the  second  to  the  fifth,  inclusive.  Then 
raise  the  piece  at  one  angle,  and  remove  it  with  as  little  disturbance  to 
the  parts  beneath  as  possible. 

In  the  skeleton,  the  superior  aperture  of  the  thorax  is  bounded 
by  the  sternum  and  first  dorsal  vertebra,  before  and  behind,  and 
by  the  first  ribs  in  the  rest  of  its  circumference.  It  is  broader 
from  side  to  side  than  from  before  backwards,  and  gives  passage 
in  the  subject  to  the  trachea,  oesophagus,  subclavian  and  carotid 
arteries  and  veins,  the  thoracic  duct,  and  several  large  nerves  ; 
the  interstices  being  closed  by  the  thoracic  fascia.  The  inferior 
boundary  or  floor  of  the  thorax  is  formed  by  the  diaphragm, 
which  extends  obliquely  from  the  ensiform  cartilage  across  the 
six  lower  ribs  to  the  first  lumbar  vertebra.  This  aperture  of  the 
thorax  is  also  broader  from  side  to  side  than  from  before  back- 
wards, and  from  the  obliquity  of  the  diaphragm  the  chest  is  much 
deeper  behind  than  before.  The  diaphragm  gives  passage  to  the 
inferior  vena  cava,  oesophagus,  aorta,  thoracic  duct,  the  azygos 
veins,  and  some  large  nerves. 

The  contents  of  the  thorax  are  the  lungs  and  the  heart, 
with  their  investing  membranes,  pleura  and  pericardium,  and 
great  vessels  ;  together  with  the  oesophagus  and  some  large 
nerves. 

26* 


306  THE   DISSECTOR. 


PLEURJE. 

The  PLEURA  are  two  serous  membranes  which  invest  the  lungs 
and  form  the  lining  of  the  cavity  of  the  chest  on  either  side. 
That  portion  of  the  membrane  which  covers  the  lung  is  termed 
pleura  pulmonalis,  and  that  which  lines  the  parietes  pleura  cos- 
talis.  Besides  forming  the  internal  lining  of  the  ribs  and  inter- 
costal muscles,  the  reflected  portion  of  the  membrane  covers  the 
upper  surface  of  the  diaphragm  and  the  thoracic  surface  of  the 
vessels  at  the  root  of  the  neck,  extending  for  somewhat  more  than 
an  inch  above  the  margin  of  the  first  rib.  At  the  lower  border 
of  the  root  of  the  lung  is  a  fold  of  the  pleura  which  extends  down 
the  side  of  the  posterior  mediastinum  to  the  diaphragm ;  this  is 
the  broad  ligament  of  the  lung,  ligamentum  latum  pulmonis.  On 
its  external  surface,  where  the  pleura  is  connected  with  surround- 
ing parts,  it  is  rough  ;  on  its  inner  surface,  smooth.  On  the 
right  side,  where  the  diaphragm  is  pressed  upwards  by  the  liver, 
the  pleura  is  shorter  than  on  the  left,  but  extends  higher  into  the 
neck  ;  while  the  left  pleura,  in  consequence  of  the  encroachment 
of  the  heart  upon  the  left  side  of  the  chest,  is  narrower  than  the 
right. 

MEDIASTINUM. — The  approximation  of  the  two  reflected  pleuraa 
in  the  middle  line  of  the  thorax  forms  a  septum  which  divides 
the  chest  into  the  two  pulmonary  cavities.  This  is  the  medias- 
tinum. The  two  pleuraB  are  not,  however,  in  contact  with  each 
other  at  the  middle  line  in  the  formation  of  the  mediastinum,  but 
have  a  space  between  them  which  contains  all  the  viscera  of  the 
chest  excepting  the  lungs.  The  mediastinum  is  divided  into  the 
anterior,  middle,  and  posterior. 

The  anterior  mediastinum  (Fig.  97,  c),  is  a  triangular  space, 
bounded  in  front  by  the  sternum,  and  on  either  side  by  the  pleura. 
It  contains  a  quantity  of  loose  cellular  tissue,  in  which  are  found 
some  lymphatic  vessels  passing  upwards  from  the  liver  ;  the  re- 
mains of  the  thymus  gland,  the  origins  of  the  sterno-hyoid,  sterno- 
thyroid,  and  left  triangularis  sternr  muscle,  and  the  left  internal 
mammary  vessels. 

The  middle  mediastinum  (Fig.  97,  7),  contains  the  heart  en- 
closed in  its  pericardium;  the  ascending  aorta;  the  superior  vena 
cava;  the  pulmonary  vessels;  the  bifurcation  of  the  trachea;  and 
the  phrenic  nerves. 

The  posterior  mediastinum  is  bounded  behind  by  the  vertebral 
column,  in  front  by  the  pericardium,  and  on  each  side  by  the 
pleura.  It  contains  the  descending  aorta  (Fig.  97,  i  o);  the 
greater  and  lesser  azygos  veins,  and  superior  intercostal  vein  ; 
the  thoracic  duct ;  the  oesophagus  and  pneumogastric  nerves  ; 
and  the  great  splanchnic  nerves. 


PLEURA. — PHRENIC  NERVES. 


307 


The  pleura  should  now  be  carefully  dissected  away  from  the  side  of 
the  pericardium,  and  from  the  root  of  the  lung  before  and  behind,  and 
also  removed  from  the  side  of  the  posterior  mediastinum  in  order  to  bring 
into  view  the  vessels  which  it  contains.  On  the  side  of  the  pericardium 
will  be  found  the  phrenic  nerve,  which,  from  its  whiteness,  is  seen  through 
the  pleura  before  that  membrane  is  removed.  On  the  front  of  the  root 
of  the  lungs  is  the  anterior  pulmonary  plexus,  behind  the  root  of  the 
lungs  the  posterior  pulmonary  plexus  and  pneumogastric  nerves  ;  while 
the  root  of  the  lungs  itself  is  composed  of  the  pulmonary  artery,  pulmo- 
nary veins  and  bronchus,  with  their  divisions. 

Fig.  97. 


A  DIAGRAM  REPRESENTING  A  TRANSVERSE  SECTION  OF  THE  CHEST,  AND  THE 
RELATIVE  POSITION  OP  THE  VISCERA. — 1.  The  right  lung.  2.  The  left  lung. 
3.  The  root  of  the  lungs,  with  the  order  of  vessels  from  before  backwards, 
shown,  v.  The  pulmonary  vein.  a.  The  pulmonary  artery,  b.  The  bronchus. 
4/4.  The  point  of  reflection  of  the  pleura,  from  the  root  of  the  lung  upon  the 
parietes.  5.  The  cavity  of  the  pleura  :  that  which  is  in  contact  with  the  lung  ia 
the  pleura  pulmonalis,  and  that  with  the  wall  of  the  chest,  pleura  costalis.  6. 
The  anterior  mediastinum,  bounded  by  the  sternum  in  front,  and  by  the  pleura 
at  each  side.  7.  The  heart,  in  the  middle  mediastinum.  8.  The  cavity  of  the 
pericardium.  9,  9.  The  phrenic  nerves,  lying  between  the  pleura  and  pericar- 
dium, in  front  of  the  root  of  the  lungs.  10.  The  descending  aorta.  11.  The 
vena  azygos.  12.  The  thoracic  duct.  13.  The  oesophagus,  accompanied  by 
the  two  pneumogastric  nerves.  These  parts,  from  No.  10  to  13,  are  all  within 
the  posterior  mediastinum,  which  is  bounded  on  each  side  by  the  pleura, 
MIL I  behind  by  the  vertebral  column.  14,  14.  The  sympathetic  nerve  at  each 
side. 

The  PHRENIC  NERVES,  the  nerves  of  the  diaphragm,  proceed 
from  the  cervical  nerves  (3d,  4th,  5th),  and  pass  in  front  of  the 
anterior  scaleni  muscles  to  enter  the  chest.  The  nerve,  on  either 
side,  then  passes  between  the  subclavian  artery  and  vein,  and 
descends  by  the  side  of  the  pericardium  in  front  of  the  root  of 


308 


THE   DISSECTOR. 


the  lungs  to  the  diaphragm,  to  which  it  is  distributed.  The  right 
phrenic  nerve  in  the  upper  part  of  the  thorax  lies  along  the  outer 
side  of  the  vena  innominata  and  superior  vena  cava.  The  left 
crosses  the  arch  of  the  aorta,  and,  having  to  follow  the  convexity 
of  the  heart,  is  somewhat  longer  than  the  right.  Each  nerve  at 
its  entrance  into  the  chest  crosses  in  front  of  the  internal  mam- 
mary artery,  and  while  in  relation  with  that  vessel  is  joined  by  a 
long  and  slender  arterial  branch,  the  comes  nervi  phrenici,  which 
accompanies  the  nerve  to  the  diaphragm.  The  phrenic  nerve 
gives  one  or  two  small  filaments  to  the  pericardium. 

THE  LUNGS. 

The  lungs  are  two  conical  organs,  situated  one  on  each  side  of 
the  chest,  embracing  the  heart,  and  separated  from  each  other 

Fig.  98. 


ANATOMY  OF  THE  HEART  AND  LUNGS. — 1.  The  right  ventricle ;  the  vessels 
to  the  left  of  the  number  are  the  middle  coronary  artery  and  veins  ;  and  those 
to  its  right,  the  anterior  coronary  artery  and  veins.  2.  The  left  ventricle.  3. 
The  right  auricle.  4.  The  left  auricle.  5.  The  pulmonary  artery.  6.  The 
right  pulmonary  artery.  7.  The  left  pulmonary  artery.  8.  The  remains  of  the 
ductus  arteriosus.  9.  The  arch  of  the  aorta.  10.  The  superior  vena  cava. 
11.  The  arteria  innominata,  and  in  front  of  it  the  right  vena  innominata.  12. 
The  right  subclavian  vein,  and  behind  it,  its  corresponding  artery.  13.  The 
right  common  carotid  artery  and  vein.  14.  The  left  vena  innominata.  15.  The 
left  carotid  artery  and  vein.  16.  The  left  subclavian  vein  and  artery.  17.  The 
trachea.  18.  The  right  bronchus.  19.  The  left  bronchus.  20,  20.  The  pul- 
monary veins;  18,  20,  form  the  root  of  the  right  lung;  and  7,  19,  20,  the  root 
of  the  left.  21.  The  superior  lobe  of  the  right  lung.  22.  Its  middle  lobe.  23. 
Its  inferior  lobe.  24.  The  superior  lobe  of  the  left  lung.  25.  Its  inferior  lobe. 


THE   LUNGS.  309 

by  that  organ  and  by  a  membranous  partition,  the  mediastinum. 
On  the  external  or  thoracic  side  they  are  convex,  and  correspond 
with  the  form  of  the  cavity  of  the  chest ;  internally  they  are  con- 
cave, to  receive  the  convexity  of  the  heart.  Superiorly  they 
terminate  in  a  tapering  cone,  which  extends  above  the  level  of 
the  first  rib  into  the  root  of  the  neck ;  and  inferiorly  they  are 
broad  and  concave,  and  rest  on  the  convex  surface  of  the  dia- 
phragm. Their  posterior  border  is  rounded,  broad  and  long ; 
the  anterior  sharp,  short,  and  marked  by  one  or  two  deep  fissures; 
and  the  inferior  border  which  surrounds  the  base  is  also  sharp. 
The  color  of  the  lungs  is  pinkish  gray,  mottled,  and  variously 
marked  with  black.  The  surface  is  figured  with  irregularly  poly- 
hedral outlines,  which  represent  the  lobules  of  the  organ,  and  the 
area  of  each  of  these  polyhedral  spaces  is  crossed  by  lighter  lines 
representing  smaller  lobules.  The  weight  of  the  lungs  is  about 
forty  ounces,  the  right  lung  being  two  ounces  heavier  than  the  left. 
Each  lung  is  divided  into  two  lobes,  by  a  long  and  deep  fissure, 
which  extends  from  the  posterior  surface  of  the  organ,  downwards 
and  forwards,  to  near  the  anterior  angle  of  its  base.  In  the  right 
lung  the  upper  lobe  is  subdivided  by  a  second  fissure,  which  runs 
obliquely  forward  from  the  middle  of  the  preceding  to  the  ante- 
rior border  of  the  organ,  and  marks  off  a  small  triangular  lobe. 
The  left  lung  presents  a  deep  notch  in  its  anterior  border  at  a 
point  corresponding  with  the  apex  of  the  heart. 

The  right  lung  is  larger  than  the  left  in  consequence  of  the 
inclination  of  the  heart  to  the  left  side.  It  is  also  shorter  from 
the  great  convexity  of  the  liver,  which  presses  the  diaphragm 
upwards  on  the  right  side  of  the  chest  considerably  above  the 
level  of  the  left;  and  it  has  three  lobes.  The  left  lung  is  smaller, 
has  but  two  lobes,  but  is  longer  than  the  right. 

Each  lung  is  retained  in  its  place  by  its  root,  which  is  formed 
by  the  pulmonary  artery,  pulmonary  veins,  and  bronchial  tubes, 
together  with  the  bronchial  vessels  and  pulmonary  plexuses  of 
nerves.  The  groove  on  the  surface  of  the  lung  where  the  vessels 
enter  its  substance  is  the  hilum  pulmonis,  and  the  position  of  the 
large  vessels  in  the  root  of  the  lung  as  follows  :  from  before  back- 
wards they  are  placed  in  a  similar  order  on  both  sides,  viz : — 

Pulmonary  veins,         Pulmonary  artery,         Bronchus. 
From  above  downwards,  on  the  right  side,  this  order  is  exactly 
reversed  ;  but  on  the  left  side,  the  bronchus  has  to  stoop  beneath 
the  arch  of  the  aorta,  which  alters  its  position  to  the  vessels. 
They  are  thus  disposed  on  the  two  sides : — 

Right.  Left. 

Bronchus,  Artery, 

Artery,  Bronchus, 

Veins.  Veins. 


310 


THE  DISSECTOR. 


The  special  relations  of  the  roots  of  the  lung  are,  for  the  right, 
the  descending  cava,  which  lies  in  front,  and  the  vena  azygos, 
which  arches  over  it  from  behind  to  terminate  in  the  superior 
vena  cava.  The  root  of  the  left  lung  has  the  descending  aorta 
lying  behind  it. 

Fig.  99. 


A  POSTERIOR  VIEW  OF  THE  THORACIC  VISCERA,  SHOWING  THEIR  RELATIVE 
POSITIONS  BY  THE  REMOVAL  OF  THE  POSTERIOR  PORTION  OF  THEIR  PARIETES. — 
1,2.  Upper  and  lower  lobes  of  the  right  lung.  3.  Interlobular  fissures.  4.  In- 
ternal portion  of  the  pleura  costalis,  forming  one  of  the  sides  of  the  posterior 
mediastinum.  5.  Twelfth  rib  and  lesser  diaphragm.  6.  Reflection  of  the  pleura 
over  the  greater  muscle  of  the  diaphragm  on  the  right  side.  7,  7.  Eight  pleura 
costalis  adhering  to  the  ribs.  8,  9.  The  two  lobes  of  the  left  lung.  10,  10. 
Interlobular  fissures.  11,  11.  The  left  pleura,  forming  the  parietes  of  the  pos- 
terior mediastinum.  12,  13.  Its  reflections  over  the  diaphragm  on  this  side.  14, 
14.  The  left  pleura  costalis  on  the  parietes  of  the  chest.  15.  The  trachea.  16. 
The  larynx.  17.  Opening  of  the  larynx  and  the  epiglottis  cartilage  in  situ.  18. 
Root  and  top  of  the  tongue.  19,  19.  Right  and  left  bronchia.  20.  The  heart 
inclosed  in  the  pericardium.  21.  Upper  portion  of  the  diaphragm  on  which  it 
rests.  22.  Section  of  the  Oesophagus.  23.  Section  of  the  aorta.  24.  Arteria 
innominata.  25.  Primitive  carotid  arteries.  26.  The  subclavian  arteries.  27. 
Internal  jugular  veins.  28.  Second  cervical  vertebra.  29.  Fourth  lumbar. 


STRUCTURE   OF  THE  LUNGS.  311 

Structure. — The  lungs  are  composed  of  the  ramifications  of  the  bron- 
chial tubes  (bronchia),  which  terminate  in  intercellular  passages  and  air- 
cells,  of  the  ramifications  of  the  pulmonary  artery  and  veins,  bronchial 
arteries  and  veins,  lymphatics  and  nerves.  The  whole  of  these  structures, 
being  held  together  by  cellular  tissue,  constitute  the  parenchyma.  The 
parenchyma  of  the  lungs,  when  examined  on  the  surface,  or  by  means  of 
a  section,  is  seen  to  consist  of  small  polyhedral  divisions,  or  lobules, 
which  are  connected  to  each  other  by  an  interlobular  cellular  tissue. 
These  lobules,  again,  consist  of  smaller  lobules  ;  and  the  latter  are  formed 
by  a  cluster  of  air-cells,  in  the  parietes  of  which  the  capillaries  of  the 
pulmonary  artery  and  pulmonary  veins  are  distributed.  Kach  lobule, 
takrn  atone,  is  provided  with  its  separate  bronchial  tube,  pulmonary 
a  rt.  TV  and  vein,  and  is  isolated  from  surrounding  lobules  by  a  process  of 
rrlluiar  membrane  derived  from  the  subserous  tissue;  and  the  entire 
lung  is  an  assemblage  of  these  lobules,  so  separated  and  so  connected, 
held  together  by  the  pleura. 

The  serous-investing  membrane  of  the  lungs  or  pleura  is  connected 
with  the  surface  of  the  lobules  by  means  of  a  subserous  cellular  tissue, 
which  forms  a  distinct  layer,  and  being  prolonged  between  the  lobules, 
is  the  bond  of  adhesion  between  them.  This  layer  contains  elastic  tis- 
sue, and  is  a  chief  source  of  the  elasticity  of  the  lungs  ;  its  interstices 
are  moistened  by  a  serous  secretion,  and  are  unincumbered  with  fat. 

Bronchial  Tubes. — The  two  bronchi  proceed  from  the  bifurcation  of  the 
trachea  opposite  the  third  dorsal  vertebra  to  their  corresponding  lungs. 
The  right,  about  an  inch  long,  takes  its  course  nearly  at  right  angles 
with  the  trachea,  and  enters  the  upper  part  of  the  right  lung  ;  while  the 
left,  two  inches  in  length,  and  smaller  than  the  right,  passes  obliquely 
beneath  the  arch  of  the  aorta,  and  enters  the  lung  at  about  the  middle  of 
its  root.  Upon  entering  the  lungs,  they  divide  into  two  branches,  and 
each  of  these  divides  and  subdivides  dichotomously  to  their  ultimate 
termination  in  the  intercellular  passages  and  air-cells. 

According  to  Mr.  Rainoy,  the  bronchial  tubes  continue  to  diminish  in 
size  until  they  attain  a  diameter  of  ^ff  to  g'ff  of  an  inch,  and  arrive  within 
£  of  an  inch  of  the  surface  of  the  lung.  They  then  become  changed  in 
structure,  and  are  continued  onwards  in  the  midst  of  air-cells,  under  the 
name  of  intercellular  passages.  Lastly,  the  intercellular  passages,  after 
several  bifurcations,  terminate,  each  by  a  caecal  extremity  or  air-cell. 
The  intercellular  passages  are  at  first  cylindrical,  like  the  bronchial 
tubes,  but  soon  become  irregular  in  shape  from  the  great  number  of  air- 
cells  which  open  into  them  on  all  sides.  The  air-cells,  in  the  adult  lung, 
measure  between  ?^ff  and  ^  of  an  inch  ;  they  are  irregular  in  shape, 
most  frequently  four-sided  cavities,  separated  by  thin  septa,  and  commu- 
nicating freely  with  the  intercellular  passages,  and  sparingly  with  the 
bronchial  tubes. 

In  structure  the  bronchial  tubes  are  composed  of  fibro-cartilages,  fibrous 
membrane,  muscular  fibres,  elastic  fibres,  and  mucous  membrane.  The 
Jibrn-cartilages  of  the  primary  divisions  of  the  trachea  are  six  or  eight  in 
number  in  the  right,  and  ten  or  twelve  in  the  left  branch.  Within  the 
lung  the  bronchial  tubes  are  cylindrical,  and  the  fibro-cartilage  assumes 
the  form  of  thin  plates  of  irregular  shape  and  size.  These  plates  are 
found  entering  into  the  structure  of  the  bronchial  tubes,  until  the  latter 
attain  a  very  minute  size  (£  of  a  line  in  diameter),  and  are  then  entirely 
lost.  The  Jibrous  membrane,  which  enters  largely  into  the  formation  of 
the  trachea  and  bronchial  tubes,  is  the  principal  coat  of  the  smallest  tubes, 


312  THE   DISSECTOR. 

and  is  continued  to  their  terminations  in  the  intercellular  passages  and 
air-cells. 

The  muscular  fibres,  belonging  to  the  class  of  non-striated  or  organic 
muscle,  are  arranged  in  circles  around  the  tube,  and  form  a  muscular 
coat  which  is  continued  as  far  as  the  tubes  themselves,  being  absent  in 
the  intercellular  passages  and  cells.  The  elastic  fibres,  arranged  in  lon- 
gitudinal fasciculi,  form  a  thin  stratum  situated  next  the  mucous  lining  ; 
this  elastic  coat  is  prolonged  to  the  ends  of  the  tubes,  and  scattered  fibres 
are  found  around  the  intercellular  passages  and  cells.  The  mucous  mem- 
brane, lining  the  bronchial  tubes,  is  provided  with  a  ciliated  columnar 
epithelium  as  far  as  their  termination  ;  but  in  the  intercellular  passages 
and  air-cells  it  is  altered  in  its  characters,  is  thin  and  transparent,  and 
coated  with  a  squamous  epithelium. 

The  capillaries  of  the  lungs  form  plexuses  which  occupy  the  walls  and 
septa  of  the  air-cells  and  the  walls  of  the  intercellular  passages,  but  are 
not  continued  into  the  bronchial  tubes.  The  septa  between  the  cells 
consist  of  a  single  layer  of  the  capillary  plexus  inclosed  in  a  fold  of  the 
mucous  lining  membrane.  The  cells  of  the  central  parts  of  the  lung  are 
most  vascular,  and  at  the  same  time  smallest,  while  those  of  the  periphery 
are  less  vascular  and  larger. 

The  pigmentary  matter  of  the  lungs  is  contained  in  the  air-cells,  as 
well  as  in  the  cellular  tissue  of  the  interlobular  spaces  and  of  the  blood- 
vessels ;  it  is  composed  chiefly  of  carbon. 

The  pulmonary  artery,  conveying  the  dark  and  impure  venous  blood  to 
the  lungs,  terminates  in  capillary  vessels,  which  form  a  minute  network 
in  the  parietes  of  the  intercellular  passages  and  air-cells,  and  then  con- 
•verge  to  form  the  pulmonary  veins,  by  which  the  arterial  blood,  purified 
in  its  passage  through  the  capillaries,  is  returned  to  the  left  auricle  of  the 
heart. 

The  bronchial  arteries,  branches  of  the  thoracic  aorta,  ramify  on  the 
parietes  of  the  bronchial  tubes,  and  terminate  partly  in  bronchial  veins 
which  convey  the  venous  blood  to  the  vena  azygos  on  the  right  side,  and 
the  superior  intercostal  vein  on  the  left ;  and  partly  in  the  pulmonary 
capillaries. 

The  lymphatics,  commencing  on  the  surface  and  in  the  substance  of  the 
lungs,  terminate  in  the  bronchial  glands.  These  glands,  very  numerous, 
and  often  of  large  size,  are  placed  at  the  roots  of  the  lungs,  around  the 
bronchi,  and  at  the  bifurcation  of  the  trachea.  In  early  life  they  resemble 
lymphatic  glands  in  other  situations  ;  but  in  old  age,  and  often  in  the 
adult,  are  black  and  filled  with  carbonaceous  matter,  and  occasionally 
with  calcareous  deposits. 

The  nerves  of  the  lungs  are  derived  from  the  pneumogastric  and  sym- 
pathetic. They  form  two  plexuses :  anterior  pulmonary  plexus,  situated 
upon  the  front  of  the  root  of  the  lungs,  and  composed  chiefly  of  filaments 
from  the  great  cardiac  plexus  ;  and  posterior  pulmonary  plexus,  on  the 
posterior  aspect  of  the  root  of  the  lungs,  composed  principally  of  branches 
from  the  pneumogastric.  The  branches  from  these  plexuses  follow  the 
course  of  the  bronchial  tubes,  and  are  distributed  to  the  intercellular 
passages  and  air-cells. 

Dissection. — After  the  pulmonary  plexuses,  anterior  and  posterior,  have 
been  dissected,  and  the  relative  position  of  the  vessels  composing  the  root 
of  the  lung  examined ;  the  latter  may  be  removed,  and  the  branches  fol- 
lowed for  some  distance  into  the  substance  of  the  lung,  in  order  to  see 
their  mode  of  division,  and  the  structure  of  the  bronchial  tubes. 


PERICARDIUM. 


313 


THE  HEART. 


The  central  organ  of  circulation,  the  heart,  is  situated  between 
the  two  layers  of  pleura  which  constitute  the  mediastinum,  and 
is  inclosed  in  a  proper  membrane,  the  pericardium. 


Fig.  100. 


FRONT  OR  UPPER  SURFACE  OF  THE 
HKAHT  AND  GREAT  VESSELS  IN- 
JKCTKI)  AND  PLACED  OBLIQUELY, 
BUT  ITS  APEX  IS  NOT  TILTED  FOR- 
WARD AS  IN  THE  BODY. — a.  Conus 
arteriosus,  or  infundibulura  of  right 
ventricle,  b.  Notch  at  apex  of  heart. 
c.  Auricular  appendage  of  right  auri- 
cle, d.  Vena  cava  superior,  e,  b. 
Anterior  longitudinal  furrow,  mark- 
ing the  division  between  the  ventri- 
cles. /.  The  aorta,  k.  Pulmonary 
artery.  /.  Right  ventricle,  of  which 
the  chief  part  is  seen  in  front,  m. 
Right  auricle,  n.  Left  auricle,  seen 
only  to  a  small  extent,  with  its  ap- 
pendage projecting  forward.  There 
is  another  letter  o,  on  the  left  ven- 
tricle. 


PERICARDIUM. — The  pericardium  is  a  fibro-serous  membrane 
like  the  dura  mater,  and  resembles  that  membrane,  also,  in  de- 

BACK  OR  UNDER  SURFACE  OF  Fig.  101. 

THK  SAMK  HKAHT. — b.  Apex  of 
heart,  slightly  notched,  c,  c. 
Pulmonary  veins,  two  on  each 
side.  d.  Auricula  of  left  auricle. 
e.  Point  of  entrance  of  coronary 
vein  into  the  back  of  right  auricle, 
m.  d,  e,  indicate  part  of  the 
transverse  or  auriculo-ventricular 
furrow,  occupied  by  the  large 
coronary  vein.  f.  The  aorta. 
/-,  k.  Right  and  left  divisions  of 
the  pulmonary  artery.  /.  Right 
ventricle,  only  the  smaller  part 
seen.  m.  The  right,  and  n,  the 
left  auricle  :  the  division  or  fur- 
row between  them  is  distinctly 
seen.  o.  The  left  ventricle,  of 
which  the  greater  part  is  seen 
behind,  r.  Orifice  of  the  vena 
cava  inferior,  constricted  by  the 
ligature  used  to  keep  in  the  in- 
jection. 

riving  its  serous  layer  from  the  reflected  serous  membrane  of  the 
viscus  which  it  incloses.     It  consists,  therefore,  of  two  layers, 
27 


314  THE   DISSECTOR. 

an  external  fibrous  and  an  internal  serous.  The  j£5?vms  layer  is 
attached,  above,  to  the  great  vessels  at  the  root  of  the  heart,  and 
adds  to  their  strength  by  contributing  a  fibrous  sheath ;  below, 
it  is  connected  with  the  tendinous  portion  of  the  diaphragm.  The 
serous  membrane  invests  the  heart,  and  surrounding  the  great 
vessels  which  proceed  from  its  root,  is  then  reflected  on  the  inner 
surface  of  the  fibrous  layer. 

The  pericardium  may  be  laid  open  from  the  front  by  means  of  a  crucial 
incision,  and  after  its  relation  to  the  heart  and  great  vessels  has  been 
examined,  the  latter  may  be  cleared  of  fat  and  cellular  tissue,  in  order 
to  see  the  nerves  and  nervous  plexuses  situated  at  the  root  of  the  heart. 
Crossing  the  arch  of  the  aorta,  to  reach  the  pericardium,  is  the  left  phrenic 
nerve.  Further  to  the  left  is  a  large  nerve  which  crosses  the  aorta  to  the 
back  of  the  root  of  the  lungs  ;  this  is  the  left pneumoqastric  nerve.  Between 
these  are  two  smaller  nerves,  especially  destined'  for  the  heart,  the  left 
superficial  cardiac  nerve,  a  branch  of  the  sympathetic,  and  the  inferior 
cardiac  branch  of  the  left  pneumoqastric.  These  nerves  should  be  traced 
to  the  concavity  of  the  arch  of  the  aorta,  where  they  unite  with  the 
superficial  cardiac  plexus.  The  latter  receives  from  behind  an  offset  from 
the  deep  cardiac  plexus,  and  descends  in  the  groove  between  the  trunk 
of  the  pulmonary  artery  and  aorta  to  the  anterior  coronary  artery,  where 
it  becomes  the  anterior  coronary  plexus.  In  following  these  plexuses  in 
the  course  now  described,  the  pericardium  must  be  divided  and  turned 
aside  in  the  direction  taken  by  the  nerves. 

The  arteries  of  the  pericardium  are  derived  from  the  numerous 
vessels  which  surround  it ;  thus  in  front  it  receives  branches  from 
the  internal  mammary  arteries ;  on  the  sides  from  the  bronchial 
arteries  ;  behind  from  the  descending  aorta  ;  and  below  from  the 
phrenic  arteries. 

The  HEART  is  placed  obliquely  in  the  chest,  the  base  being  di- 
rected upwards  and  backwards  towards  the  right  shoulder ;  the 
apex  forwards  and  to  the  left,  pointing  to  the  space  between  the 
fifth  and  sixth  ribs,  at  about  two  or  three  inches  from  the  ster- 
num.1 Its  under  side  is  flattened,  and  rests  upon  the  tendinous 
portion  of  the  diaphragm  ;  its  upper  side  is  rounded  and  convex, 
and  formed  principally  by  the  right  ventricle,  and  partly  by  the 
left.  Surmounting  the  ventricles  are  the  corresponding  auricles, 
whose  auricular  appendages  are  directed  forwards,  and  slightly 
overlap  the  root  of  the  pulmonary  artery.  The  pulmonary  artery 
is  the  large  anterior  vessel  at  the  root  of  the  heart ;  it  crosses 
obliquely  the  commencement  of  the  aorta. 

The  heart  consists  of  two  auricles  and  two  ventricles,  which 
are  respectively  named,  from  their  position,  right  and  left.  The 
right  is  the  venous  side  of  the  heart ;  it  receives  into  its  auricle 
the  venous  blood  from  every  part  of  the  body,  by  the  superior 

1  The  size  of  the  heart  is  about  five  inches  in  length,  three  inches  and 
a  half  in  greatest  breadth,  and  two  and  a  half  in  thickness.  Its  weight 
is  about  eleven  ounces  in  the  male,  and  nine  ounces  in  the  female. 


THE    HEART.  315 

and  inferior  cava  and  coronary  vein.  From  the  auricle  the 
blood  passes  into  the  ventricle,  and  from .  the  ventricle  through 
the  pulmonary  artery,  to  the  capillaries  of  the  lungs.  From 
these  it  is  returned  as  arterial  blood  to  the  left  auricle ;  from  the 
left  auricle  it  passes  into  the  left  ventricle ;  and  from  the  left  ven- 
tricle is  carried  through  the  aorta,  to  be  distributed  to  every  part 
of  the  body,  and  again  returned  to  the  heart  by  the  veins.  This 
constitutes  the  course  of  the  adult  circulation. 

The  heart  is  best  studied  in  situ.  If,  however,  it  be  removed  from  the 
body,  it  should  be  placed  in  the  position  indicated  in  the  above  descrip- 
tion of  its  situation.  A  transverse  incision  should  then  be  made  along 
the  ventricular  margin  of  the  right  auricle,  from  the  appendix  to  its  right 
border,  and  crossed  by  a  perpendicular  incision,  carried  from  the  side  of 
the  superior  to  the  inferior  cava.  The  blood  must  then  be  removed. 
Stm<>  fine  specimens  of  white  fibrin  are  frequently  found  with  the  coa- 
gula  ;  occasionally  they  are  yellow  and  gelatinous.  This  appearance 
deceived  the  older  anatomists,  who  called  these  substances  "  polypus  of 
tin-  heart:"  they  are  frequently  found  in  the  right  ventricle,  and  some- 
tiiiu-s  in  the  left  cavities. 

The  RIGHT  AURICLE  is  larger  than  the  left,  and  consists  of  a 
principal  cavity  or  sinus,  and  an  appendix  auricula?.  The  inte- 
rior of  the  sinus  presents  for  examination  five  openings  ;  two 
valves  ;  two  relics  of  frctal  structure ;  and  two  peculiarities  in 
the  proper  structure  of  the  auricle.  To  facilitate  remembrance, 
they  may  be  thus  arranged  : — 

Openings.  Valves. 

Superior  cava,  Eustachian  valve, 

Inferior  cava,  Coronary  valve. 

Coronary  vein  ReKcU  of  F(£tal  Structure. 

Foramina  Thebesn,  .. 

Auriculo-ventricular  opening.         Annulus  ovalis, 

Fossa  ovalis. 
Structure  of  the  Auricle. 

Tuberculum  Loweri, 
Musculi  pectinati. 

The  superior  cava  returns  the  blood  from  the  upper  half  of  the 
body,  and' opens  into  the  upper  and  back  part  of  the  auricle. 

The  inferior  cava  returns  the  blood  from  the  lower  half  of  the 
body,  and  opens  through  the  lower  and  posterior  wall,  close  to 
the;  partition  between  the  auricles  (septum  auricularum).  The 
direction  of  these  two  vessels  is  such,  that  a  stream  forced  through 
the  superior  cava  would  be  directed  towards  the  anriculo-ventri- 
cular  opening.  In  like  manner,  a  stream  rushing  upwards  by 
the  inferior  cava  would  force  its  current  against  the  septum  auri- 
cularum ;  this  is  the  proper  direction  of  the  two  currents  during 
foetal  life. 

The  coronary  vein  returns  the  venous  blood  from  the  substance 


316  THE   DISSECTOR. 

of  the  heart ;  it  opens  into  the  auricle  between  the  inferior  cava 
and  the  auriculo-ventricular  opening,  under  cover  of  the  coro- 
nary valve. 

The  foramina  Thebesii  are  minute  pore-like  openings  of  small 
veins  which  issue  directly  from  the  muscular  structure  of  the 
heart  without  entering  the  general  venous  current.  These  open- 
ings are  also  found  in  the  left  auricle,  and  in  the  right  and  left 
ventricles,  but  are  generally  believed  to  be  mere  caecal  depres- 
sions. 

The  auriculo-ventricular  opening  is  the  large  opening  of  com- 
munication between  the  auricle  and  ventricle. 

The  Eustachian  valve  is  a  part  of  the  apparatus  of  foetal  circu- 
lation, and  serves  to  direct  the  placental  blood  from  the  inferior 
cava,  through  the  foramen  ovale  into  the  left  auricle.  In  the 
adult  it  is  a  mere  .vestige  and  imperfect,  though  sometfmes  it 
remains  of  large  size.  It'is  formed  by  a  fold  of  the  lining  mem- 
brane of  the  auricle,  containing  some  muscular  fibres,  is  situated 
between  the  aperture  of  the  inferior  cava  and  the  auriculo-ventri- 
cular opening,  and  is  generally  connected  with  the  coronary 
valve. 

The  coronary  valve  is  a  semilunar  fold  of  the  lining  membrane, 
stretching  across  the  mouth  of  the  coronary  vein,  and  preventing 
the  reflux  of  blood  in  the  vein  during  the  contraction  of  the 
auricle. 

The  annulus  ovalis  is  situated  .on  the  septum  auricularum, 
opposite  the  termination  of  ^the  inferior  cava.  It  is  the  rounded 
margin  of  the  septum,  which  occupies  the  place  of  the  foramen 
ovale  of  the  foetus. 

The  fossa  ovalis  is  an  oval  depression  corresponding  with  the 
foramen  ovale  of  the  foetus.  This  opening  is  closed  at  birth  by 
a  thin  valvular  layer,  which  is  continuous  with  the  left  margin  of 
the  annulus,  and  is  frequently  imperfect  at  its  upper  part.  The 
depression  or  fossa  in  the  right  auricle  results  from  this  arrange- 
ment. There  is  no  fossa  ovalis  in  the  left  auricle. 

The  tuberculum  Loweri  is  the  portion  of  auricle  intervening 
between  the  openings  of  the  superior  and  inferior  cava.  Being 
thicker  than  the  walls  of  the  veins,  it  forms  a  projection,  which 
was  supposed  by  Lower  to  direct  the  blood  from  the  superior 
cava  into  the  auriculo-ventricular  opening. 

The  musculi  pectinati  are  small  muscular  columns  situated  in 
the  appendix  auriculae.  They  areo  numerous,  and  arranged  pa- 
rallel with  each  other;  hence  their  cognomen,  "  pectinati, "  like 
the  teeth  of  a  comb. 

The  RIGHT  or  ANTERIOR  VENTRICLE  is  triangular  and  prismoid 
in  form.  Its  anterior  side  is  convex,  and  forms  the  larger  por- 
tion of  the  front  of  the  heart.  The  posterior  side,  which  is  also 


THE   HEART. 


317 


inferior,  is  flat,  and  rests  on  the  diaphragm  ;  the  inirer  side  cor- 
responds with  the  partition  between  the  two  ventricles,  septum 


THE  CAVITIES  OF  THE  HEART.  Fig.  102. 

— 1.  The  right  auricle.  2.  The 
entrance  of  the  superior  cava. 
3.  The  entrance  of  the  inferior 
cava.  4.  The  opening  of  the 
coronary  vein,  half  closed  hy  its 
valve.  5.  The  Eustachian  valve. 
6.  The  fossa  ovalis,  surrounded 
by  the  annulus  ovalis.  7.  The 
tuberculumLoweri.  8.  Themus- 
culi  pectinati.  9.  The  auriculo- 
ventricular  opening.  10.  The 
right  ventricle.  11.  The  tri- 
cuspid  valve,  attached  by  the 
chordao  tendinese  to  the  carneao 
columnae,  12.  13.  The  pulmo- 
nary artery,  guarded  at  its  com- 
mencement by  three  semilunar 
valves.  14.  The  right  pulmo- 
nary artery,  passing  beneath  the 
arch  and  behind  the  ascending 
aorta.  15.  The  left  pulmonary 
artery,  crossing  in  front  of  the 

descending  aorta.  *  The  remains  of  the  ductus  arteriosus,  acting  as  a  ligament 
between  the  pulmonary  artery  and  arch  of  the  aorta.  The  arrows  mark  the 
course  of  the  venous  blood  through  the  right  side  of  the  heart.  Entering  the 
auricle  by  the  superior  and  inferior  cavaD,  it  passes  through  the  auriculo-ventri- 
cular  opening  into  the  ventricle,  and  thence  through  the  pulmonary  artery  to 
the  lungs.  16.  The  left  auricle.  17.  The  openings  of  the  four  pulmonary 
veins.  18.  The  auriculo-ventricular  opening.  19.  The  left  ventricle.  20.  The 
mitral  valve,  attached  by  its  chorda)  tendineae  to  two  large  columnae  carneoe, 
which  project  from  the  walls  of  the  ventricle.  21.  The  commencement  and 
course  of  the  ascending  aorta  behind  the  pulmonary  artery,  marked  by  an  arrow. 
The  entrance  of  the  vessel  is  guarded  by  three  semilunar  valves.  22.  The  arch 
of  the  aorta.  The  comparative  thickness  of  the  two  ventricles  is  shown  in  the 
diagram.  The  course  of  the  pure  blood  through  the  left  side  of  the  heart  is 
iiuirkt'd  by  arrows.  The  blood  is  brought  from  the  lungs  by  the  four  pulmonary 
veins  into  the  left  auricle,  and  passes  through  the  auriculo-ventricular  opening 
into  the  left  ventricle,  from  whence  it  is  conveyed  by  the  aorta  to  every  part  of 
the  body. 

vriitricnlornm.  Superiorly,  where  the  pulmonary  artery  arises, 
there  is  a  dilatation  of  the  ventricle,  termed  the  infundibulum, 
or  conus  arteriosus. 

The  right  ventricle  is  to  be  laid  open  by  making  an  incision  parallel 
with,  and  a  little  to  the  right  of,  the  anterior  longitudinal  furrow,  from 
the  pulmonary  artery  in  front  to  the  apex  of  the  heart,  and  thence  by  the 
side  of  the  posterior  longitudinal  furrow  behind  to  the  auriculo-ventricu- 
lar opening. 

It  contains,  to  be  examined,  two  openings,  the  anriculo  ven- 
tricular and  that  of  the  pulmonary  artery  ;  two  apparatus  of 
valves,  the  tricuspid  and  semilunar ;  and  a  muscular  and  tendi- 

27* 


318  THE   DISSECTOR. 

nous  apparatus  belonging  to  the  tricuspid  valves.     They  may  be 
thus  arranged  : — 

Auriculo-ventricalar  opening,  Tricuspid  valves, 

Opening  of  the  pulmonary  artery,       Semilunar  valves, 

Chorda3  tendineae, 

Column*  earner. 

The  auriculo-ventricular  opening  is  surrounded  by  a  fibrous 
ring,  covered  by  the  lining  membrane  (endocardium)  of  the  heart. 
It  is  the  opening  of  communication  between  the  right  auricle  and 
ventricle. 

The  opening  of  the  pulmonary  artery  is  situated  at  the  summit 
of  the  conus  arteriosus,  close  to  the  septum  ventriculorum,  on 
the  left  side  of  the  right  ventricle,  and  upon  the  anterior  aspect 
of  the  heart. 

The  tricuspid  valves  are  three  triangular  folds  of  the  lining 
membrane,  strengthened  by  a  thin  layer  of  fibrous  tissue.  They 
are  connected  by  their  base  around  the  auriculo-ventricular  open- 
ing ;  and  by  their  sides  and  apices,  which  are  thickened,  they  give 
attachment  to  a  number  of  slender  tendinous  cords,  called  chordae 
tendinese.  The  chordae  tendinece  are  the  tendons  of  the  thick 
muscular  columns  (columnce  carnece)  which  stand  out  from,  the 
walls  of  the  ventricle,  and  serve  as  muscles  to  the  valves.  A 
number  of  these  tendinous  cords  converge  to  a  single  muscular 
attachment.  The  tricuspid  valves  prevent  the  regurgitation  of 
blood  into  the  auricle  during  the  contraction  of  the  ventricle,  and 
they  are  prevented  from  being  themselves  driven  back  by  the 
chordae  tendineaa  and  their  muscular  attachments. 

This  connection  of  the  muscular  columns  of  the  heart  to  the 
valves  has  caused  their  division  into  active  and  passive.  The 
active  valves  are  the  tricuspid  and  mitral ;  the  passive,  the  semi- 
lunar  and  coronary. 

The  valves  consist,  according  to  Mr.  King,1  of  curtains,  cords, 
and  columns.  The  anterior  valve  or  curtain  is  the  largest,  and 
is  so  placed  as  to  prevent  the  filling  of  the  pulmonary  artery 
during  the  distension  of  the  ventricle.  The  right  valve  or  curtain 
is  of  smaller  size,  and  is  situated  on  the  right  side  of  the  auriculo- 
ventricular  opening.  The  third  valve,  or  "fixed  curtain,"  is 
connected  by  its  cords  to  the  septum  ventriculorum.  The  cords 
(chordae  tendinea?)  of  the  anterior  curtain  are  attached,  princi- 
pally, to  a  long  column  (columna  carnea),  which  is  connected 
with  the  "  right  or  thin  and  yielding  wall  of  the  ventricle."  From 
the  lower  part  of  this  column  a  transverse  muscular  band,  the 

1  "  Essay  on  the  Safety-Valve  Function  in  the  Right  Ventricle  of  the 
Human  Heart,"  by  T.  W.  King.  Guy's  Hospital  Reports,  vol.  ii. 


THE    HEART.  319 

"long  moderator  band,"  is  stretched  to  the  septum  ventriculorum, 
or  "  solid  wall"  of  the  ventricle.  The  right  curtain  is  connected, 
by  means  of  its  cords,  partly  with  the  long  column,  and  partly 
with  its  own  proper  column,  the  second  column,  which  is  also 
attached  to  the  "yielding  wall"  of  the  ventricle.  A  third  and 
smaller  column  is  generally  connected  with  the  right  curtain. 
The  "fixed  curtain"  is  so  named  from  its  attachment  to  the 
"  solid  wall"  of  the  ventricle,  by  means  of  cords  only,  without 
fleshy  columns. 

Prom  this  arrangement  of  the  valves  it  follows,  that  if  the  right 
ventricle  be  over  distended,  the  thin  or  "yielding  wall"  will  give 
way,  and  carry  with  it  the  columns  of  the  anterior  and  right  valves. 
The  cords  connected  with  these  columns  will  draw  down  the  edges 
of  the  corresponding  valves,  and  produce  an  opening  between  the 
curtains,  through  which  the  superabundant  blood  may  escape 
into  the  auricle,  and  the  ventricle  be  relieved  from  over-pressure. 
This  mechanism  is  therefore  adapted  to  fulfil  the  function  of  a 
safety  valve. 

The  columnce  camece  (fleshy  columns)  is  a  name  expressive  of 
the  appearance  of  the  internal  walls  of  the  ventricles,  which,  with 
the  exception  of  the  infundibulum,  seem  formed  of  muscular  col- 
umns interlacing  in  almost  every  direction.  They  are  divided, 
according  to  the  manner  of  their  connection,  into  three  sets.  1. 
The  greater  number  are  attached  by  the  whole  of  one  side,  and 
merely  form,  convexities  into  the  cavity  of  the  ventricle.  2.  Others 
are  connected  by  both  extremities,  being  free  in  the  middle.  3. 
A  few  (columnae  papillares)  are  attached  by  one  extremity  to  the 
walls  of  the  heart,  and  by  the  other  give  insertion  to  the  chordae 
tendineae. 

The  semilunar  valves,  three  in  number,  are  situated  around  the 
commencement  of  the  pulmonary  artery,  being  formed  by  a  folding 
of  its  lining  membrane,  strengthened  by  a  thin  layer  of  fibrous 
tissue.  They  are  attached  by  their  convex  borders,  and  free  by 
the  concave,  which  are  directed  upwards  in  the  course  of  the 
vessel,  so  that,  during  the  current  of  the  blood  along  the  artery" 
they  are  pressed  against  the  sides  of  the  cylinder ;  but  if  any 
attempt  at  regurgitation  ensue,  they  are  immediately  expanded, 
nnd  effectually  close  the  entrance  of  the  tube.  The  margins  of 
the  valves  are  thicker  than  the  rest  of  their  extent,  and  each  valve 
presents  in  the  centre  of  this  margin  a  small  fibro-cartilaginous 
tubercle  or  nodule,  called  corpus  Arantii,  which  locks  in  with  'the 
other  two  Huring  the  closure  of  the  valves,  and  secures  the  tri- 
angular space  which  would  otherwise  be  left  by  the  approximation 
of  three  semilunar  folds.  On  either  side  of  the  nodule  the  edge 
of  the  valve  is  folded  and  thin,  and  to  this  part  the  term  lunula 


320  THE   DISSECTOR. 

has  been  applied.  When  the  valves  are  closed,  the  lunulse  are 
brought  in  contact  with  each  other  by  their  surfaces. 

Between  the  semilunar  valves  and  the  cylinder  of  the  artery 
are  three  pouches,  called  the  pulmonary  sinuses  (sinuses  of  Yal- 
salva).  Similar  sinuses  are  situated  behind  the  valves  at  the 
commencement  of  the  aorta,  and  are  larger  and  more  capacious 
than  those  of  the  pulmonary  artery. 

The  pulmonary  artery  commences  by  a  scalloped  border,  cor- 
responding with  the  three  valves  which  are  attached  along  its 
edge.  It  is  connected  to  the  ventricle  by  muscular  fibres,  and  by 
the  lining  membrane  of  the  heart. 

The  LEFT  OR  POSTERIOR  AURICLE  is  somewhat  smaller,  but 
thicker,  than  the  right ;  of  a  cuboid  form,  and  situated  more  pos- 
teriorly. The  appendix  auriculae  is  constricted  at  its  junction 
with  the  auricle,  and  has  a  foliated  appearance;  it  is  directed 
forwards  towards  the  root  of  the  pulmonary  artery,  to  which  the 
auriculae  of  both  sides  appear  to  converge. 

The  left  auricle  is  to  "be  laid  open  by  a  _i_  shaped  incision,  the  hori- 
zontal section  being  made  along  the  border  which  is  attached  to  the  base 
of  the  ventricle. 

It  presents  for  examination  five  openings,  and  the  muscular 
structure  of  the  appendix  ;  the  fossa  oval  is,  as  previously  ob- 
served, is  not  seen  on  the  left  side  of  the  septum  auricularum. 
The  parts  to  be  examined  are — 

Four  pulmonary  veins, 
Auriculo-ventricular  opening, 
Musculi  pectinati. 

The  pulmonary  veins,  two  from  the  right  and  two  from  the 
left  lung,  open  into  the  corresponding  sides  of  the  auricle.  The 
two  left  pulmonary  veins  terminate  frequently  by  a  common 
opening. 

The  auricula-ventricular  opening  is  the  aperture  of  communi- 
cation between  the  auricle  and  ventricle. 

.  The  musculi  pectinati  are  fewer  in  number  than  in  the  right 
auricle,  and  are  situated  only  in  the  appendix  auriculas. 

LEFT  VENTRICLE. — The  left  ventricle  is  to  be  opened  by  making 
an  incision  a  little  to  the  left  of  the  septum  ventriculorum,  and 
continuing  it  around  the  apex  of  the  heart  to  the  auriculo-ven- 
tricular  opening  behind. 

The  left  ventricle  is  conical,  both  in  external  figure  and  in  the 
form  of  its  internal  cavity.  It  forms  the  apex  of  the  heart,  by 
projecting  beyond  the  right  ventricle,  while  the  latter  has  the 
advantage  in  length  towards  the  base.  Its  walls  are  about  seven 
lines  in  thickness,  those  of  the  right  ventricle  being  about  two 
lines  and  a  half. 


THE   HEART.  321 

It  presents  for  examination,  in  its  interior,  two  openings,  two 
valves,  and  the  tendinous  cords  and  muscular  columns;  they  may 
be  thus  arranged  : — 

Auriculo-ventricular  opening,  Mitral  valves, 

Aortic  opening,  Semilunar  valves, 

Chordae  tendinea3, 
Column®  carnese. 

The  auricula-ventricular  opening  is  a  dense  fibrous  ring,  covered 
by  the  endocardium,  but  smaller  in  size  than  that  of  the  right 
side.  Its  fibrous  structure  is  closely  connected  with  that  of  the 
right  auriculo-ventricular  and  aortic  rings;  and  at  the  junction  of 
the  three  there  is  afibro-cartilaginous  mass,  and,  in  some  animals, 
a  portion  of  bone.  . . 

The  mitral  valves  are  attached  around  the  auriculo-ventricular 
opening,  as  are  the  tricuspid  in  the  right  ventricle.  They  are 
thicker  than  the  tricuspid,  and  consist  of  two  segments,  of  which 
the  larger  is  placed  between  the  auriculo-ventricular  opening  and 
the  commencement  of  the  aorta,  and  acts  the  part  of  a  valve  to 
that  foramen  during  the  filling  of  the  ventricle.  The  difference 
in  size  of  the  two  valves,  both  being  triangular,  and  the  space 
between  them,  has  given  rise  to  the  idea  of  a  "bishop's  mitre," 
after  which  they  were  named.  These  valves,  like  the  tricuspid, 
are  furnished  with  an  apparatus  of  tendinous  cords,  chordae 
tendinece,  which  are  attached  to  two  very  large  columnce  carnea. 

The  columnce  carnece  admit  of  the  same  arrangement,  into 
three  kinds,  as  on  the  right  side.  Those  which  are  free  by  one 
extremity,  the  column®  papillares,  are  two  in  number,  and  larger 
than  those  on  the  opposite  side ;  one  being  placed  on  the  left 
wall  of  the  ventricle,  and  the  other  at  the  junction  of  the  septum 
ventriculorum  with  the  posterior  wall. 

The  semilunar  valves  are  placed  around  the  commencement  of 
the  aorta,  like  those  of  the  pulmonary  artery  ;  they  are  similar  in 
structure,  and  are  attached  to  the  scalloped  border  by  which  the 
aorta  is  connected  with  the  ventricle.  The  nodule  in  the  centre 
of  each  fold  is  larger  than  those  in  the  pulmonary  valves,  and  it 
was  these  that  Arantius  particularly  described ;  but  the  term 
"  corpora  Arantii"  is  now  applied  indiscriminately  to  both.  The 
fossas  between  the  semilunar  valves  and  the  cylinder  of  the  artery 
are  larger  than  those  of  the  pulmonary  artery;  they  are  called 
the  "  sinus  aortici"  (sinuses  of  Valsalva). 

Structure. — The  heart  is  composed  of  muscular  fibres,  which  are  inter- 
posed between  two  membranes — the  pericardium  externally,  and  endo- 
cardium within — and  are  attached  to  the  fibrous  rings  which  surround 
the  four  great  openings  in  the  root  of  the  heart — the  auriculo-ventricular 
openings,  and  those  of  the  pulmonary  artery  and  aorta. 

The  fibres  of  the  ventricles,  taking  their  origin  from  these  rings,  wind 


322  THE   DISSECTOR. 

spirally  around  each  ventricle,  to  the  apex  of  the  heart,  and  then  turn 
abruptly  inwards  so  as  to  form  an  internal  layer  to  the  preceding.  The 
greater  part  of  these  recurrent  fibres  proceed  to  the  fibrous  rings,  into 
which  they  are  inserted,  while  some  constitute  the  columnse  papillares. 
A  superficial  set  of  fibres  forms  a  thin  stratum,  which  winds  around  both 
ventricles  and  binds  them  together. 

The  fibres  of  the  auricles,  like  those  of  the  ventricles,  arise  from  the 
fibrous  rings,  and,  after  winding  more  or  less  obliquely  and  transversely 
around  the  auricles — some  passing  the  two  to  form  the  septum  auricu- 
larum— return  to  be  inserted  into  the  fibrous  rings.  Some  of  the  fibres 
are  disposed  in  circles  around  the  openings  of  the  large  veins. 

The  endocardium  is  the  serous  lining  membrane  of  the  heart.  It  is  thin 
and  transparent,  but  somewhat  thicker  and  less  transparent  on  the  left 
side  than  on  the  right.  It  forms  the  folds  which,  thickened  by  fibrous 
tissue,  constitute  the  valves  of  the  heart,  and  is  continuous,  at  the  aper- 
tures, with  the  internal  coat  of  the  arteries  and  veins. 

VESSELS  OF  THE  HEART. — The  vessels  of  the  heart  maybe 
examined  either  before  or  after  the  dissection  of  the  organ,  as 
may  best  suit  the  convenience  of  the  student.  This  might  be 
done  on  the  subject ;  but  as  there  are  many  more  important 
things  to  study,  and  decay  is  rapid  in  its  march,  the  student  would 
do  well  to  obtain  a  heart  specially  for  the  dissection  of  the  ves- 
sels, and  prepare  them  for  that  purpose  by  injection  with  colored 
tallow. 

The  CORONARY  ARTERIES  arise  from  the  aortic  sinuses  at  the 
commencement  of  the  ascending  aorta,  immediately  above  the 
free  margin  of  the  semilunar  valves.  The  left,  or  anterior  coro- 
nary, passes  forwards  between  the  pulmonary  artery  and  left 
appendix  auriculae,  and  divides  into  two  branches  ;  one  of  which 
winds  around  the  base  of  the  left  ventricle  in  the  auriculo-ventri- 
cnlar  groove,  and  inosculates  with  the  right  coronary,  forming  an 
arterial  circle  around  the  base  of  the  heart ;  while  the  other 
passes  along  the  line  of  union  of  the  two  ventricles,  upon  the 
anterior  aspect  of  the  heart,  to  its  apex,  where  it  anastomoses 
with  the  descending  branch  of  the  right  coronary.  It  supplies 
the  left  auricle  and  the  anterior  surface  of  both  ventricles. 

The  right  or  posterior  coronary  passes  forward  between  the 
root  of  the  pulmonary  artery  and  the  right  auricle,  and  winds 
along  the  auriculo-ventricular  groove  to  the  posterior  longitu- 
dinal furrow,  where  it  descends  upon  the  posterior  aspect  of  the 
heart  to  its  apex,  and  inosculates  with  the  left  coronary.  It  is 
distributed  to  the  right  auricle,  and  to  the  posterior  surface  of 
both  ventricles,  and  sends  a  large  branch  along  the  sharp  margin 
of  the  right  ventricle  to  the  apex  of  the  heart. 

Cardiac  Veins. — The  veins  returning  the  blood  from  the  sub- 
stance of  the  heart  are  the — 

Great  cardiac  vein,  Anterior  cardiac  veins, 

Posterior  cardiac  veins,  Yense  Thebesii. 


NERVES   OF   THE    HEART.  323 

The  great  cardiac  vein  (coronary)  commences  at  the  apex  of  the 
heart,  and  ascends  along  the  anterior  longitudinal  groove  to  the 
base  of  the  ventricles  ;  it  then  curves  around  the  left  auriculo- 
ventricular  groove  to  the  posterior  part  of  the  heart,  where  it 
terminates  in  the  right  auricle.  It  receives  in  its  course  the  left 
cardiac  veins  from  the  left  auricle  and  ventricle,  and  the  posterior 
cardiac  veins  from  the  posterior  longitudinal  groove. 

The  posterior  cardiac  vein,  frequently  two  in  number,  com- 
mences also  at  the  apex  of  the  heart,  and  ascends  along  the 
posterior  longitudinal  groove,  to  terminate  in  the  great  cardiac 
vein.  It  receives  the  veins  from  the  posterior  aspect  of  the  two 
ventricles. 

The  anterior  cardiac  veins  collect  the  blood  from  the  anterior 
surface  of  the  right  ventricle;  one  larger  than  the  rest  runs  along 
the  right  border  of  the  heart  and  joins  the  trunk  formed  by  these 
veins,  which  curves  around  the  right  auriculo-ventricular  groove, 
to  terminate  in  the  great  cardiac  vein  near  its  entrance  into  the 
right  auricle;  others  cross  the  groove,  and  open  directly  into  the 
auricle. 

The  vence  TTiebesii  (vena3  minima)),  are  numerous  minute  ve- 
nules  which  convey  the  venous  blood  directly  from  the  substance 
of  the  heart  into  the  right  auricle.  Their  existence  is  denied  by 
some  anatomists. 

NERVES  OF  THE  HEART. — The  heart  is  supplied  with  nerves  by 
the  superficial  and  deep  cardiac  plexuses. 

The  superficial  cardiac  plexus  is  situated  immediately  beneath 
the  arch  of  the  aorta  and  in  front  of  the  right  pulmonary  artery. 
It  receives  the  superficial  cardiac  nerve  of  the  left  side  and  the 
inferior  cardiac  branch  of  the  left  pneumogastric  nerve,  both  of 
which  cross  the  arch  of  the  aorta  between  the  left  phrenic  and 
pneumogastric  nerve.  It  receives  besides  numerous  filaments 
from  the  deep  cardiac  plexus,  and  sometimes  a  cardiac  branch 
from  the  right  pneumogastric  nerve.  Connected  with  the  plexus 
is  a  small  ganglion  (sometimes  wanting),  the  cardiac  ganglion  of 
Wrisber«r,  which  lies  close  to  the  right  side  of  the  fibrous  cord 
of  the  ductus  arteriosus.  The  superficial  cardiac  plexus  gives 
off  fihmients  which  pass  along  the  front  of  the  left  pulmonary 
artery  to  the  root  of  the  left  lung,  where  they  communicate  with 
the  anterior  pulmonary  plexus;  while  the  principal  part  of  the 
plexus  descends  in  the  groove  between  the  pulmonary  artery  and 
the  aorta  to  the  anterior  longitudinal  sulcus  of  the  heart,  where 
it  comes  into  relation  with  the  anterior  coronary  artery,  and  be- 
comes the  anterior  coronary  plexus.  At  the  base  of  the  heart 
the  anterior  coronary  plexus  receives  several  filaments  from  the 
deep  cardiac  plexus.  Its  branches  are  distributed  to  the  sub- 


324  THE   DISSECTOR. 

stance  of  the  heart  in  the  course  of  the  anterior  coronary 
artery. 

The  deep  cardiac  plexus  (great  cardiac  plexus),  is  situated  in 
a  triangular  space,  bounded  in  front  by  the  arch  of  the  aorta, 
behind  by  the  trachea,  its  point  of  bifurcation,  and  below  by  the 
right  pulmonary  artery. 

The  dissection  of  this  plexus  requires  the  removal  of  the  arch  of  the 
aorta,  and,  like  the  examination  of  the  coronary  arteries,  had  better  be 
made  on  a  heart  procured  specially  for  the  purpose. 

The  deep  cardiac  plexus  receives  all  the  cardiac  branches  of 
the  sympathetic  with  the  exception  of  the  nervus  superficialis 
cordis  of  the  left  side ;  and  all  the  cardiac  branches  of  the  pneu- 
mogastric  excepting  the  left  inferior  branch.  It  gives  off  nu- 
merous filaments;  some,  proceeding  from  its  right  side,  pass  in 
front  of  the  right  pulmonary  artery  to  reach  the  right  anterior 
pulmonary  plexus;  others  descend  along  the  trunk  of  the  pulmo- 
nary artery  to  join  the  anterior  coronary  plexus  ;  and  a  third  set 
pass  behind  the  pulmonary  artery  to  the  posterior  coronary 
plexus  and  right  auricle.  The  filaments  proceeding  from  its  left 
side  are  directed,  some  forwards  beneath  the  arch  of  the  aorta  to 
join  the  superficial  cardiac  plexus,  some  outwards  to  the  left  an- 
terior pulmonary  plexus,  and  some  to  the  left  auricle;  while  the 
great  bulk  are  continued  downwards  to  the  posterior  coronary 
artery,  and  become  the  posterior  coronary  plexus,  which  supplies 
the  muscular  structure  of  the  posterior  aspect  of  the  heart. 

GREAT  VESSELS  OF  THE  HEART. 

The  great  vessels  connected  with  the  heart  are  the  pulmonary 
artery,  aorta,  superior  and  inferior  cava,  and  four  pulmonary 
veins. 

PULMONARY  ARTERY. — The  pulmonary  artery  is  the  most  an- 
terior of  the  vessels  at  the  root  of  the  heart.  It  arises  from  the 
left  side  of  the  base  of  the  right  ventricle,  that  part  termed  the 
infundibulum;  and  ascends  for  the  space  of  two  inches  to  the 
under  side  of  the  arch  of  the  aorta,  where  it  divides  into  two 
branches  of  nearly  equal  size,  the  right  and  left  pulmonary  ar- 
teries ;  the  left  branch,  just  at  its  point  of  division,  being  con- 
nected with  the  aorta  by  a  fibrous  cord,  the  remains  of  the  ductus 
arteriosus  of  the  foetus.  At  its  origin  the  pulmonary  artery  is 
in  relation  on  either  side  with  an  appendix  auricula  and  one  of 
the  coronary  arteries;  and  behind  it  has  the  commencement  of 
the  aorta  and  left  auricle.  It  is  inclosed  by  the  pericardium  for 
nearly  the  whole  of  its  length,  its  trunk  and  that  of  the  aorta 
being  contained  in  the  same  sheath  of  serous  membrane. 

The  right  pulmonary  artery,  longer  and  somewhat  larger  than 
the  left,  passes  transversely  outwards  behind  the  ascending  aorta 


AORTA 


325 


and  superior  vena  cava  to  the  root  of  the  right  lung,  where  it 
divides  into  three  branches  for  the  three  lobes.  In  its  course  it 
lies  parallel  with  and  in  front  of  the  right  bronchus. 

THE    LARGE    VESSELS  Fig.  103. 

WHICH  PROCEED  FROM  THE 
ROOT  OP  THE  HEART,  WITH 
THEIR  RELATIONS  ;  THE 
HEART  HAS  BEEN  REMOV- 
ED.— 1.  The  ascending  aor- 
ta. 2.  The  arch.  3.  The 
thoracic  portion  of  the  de-r 
scending  aorta.  4.  The  ar- 
teria  innominata  dividing 
into,  5,  the  right  carotid, 
which  again  divides,  at  6, 
into  the  external  and  in- 
ternal carotid ;  and  7,  the 
right  subclavian  artery.  8. 
The  axillary  artery ;  its  ex- 
tent is  designated  by  a 
dotted  line.  9.  The  bra- 
ehiul  artery.  10.  The  right 
pneumogastric  nerve  run- 
ning by  the  side  of  the  com- 
mon carotid,  in  front  of  the 
right  subclavian  artery, 
and  behind  the  root  of  the 
right  lung.  11.  The  left 
common  carotid,  having  to 
its  outer  side  the  left  pneu- 
mogastric nerve,  which 
crosses  the  arch  of  the  aorta, 
and  as  it  reaches  its  lower 
border  is  seen  to  give  off 
the  left  recurrent  nerve. 
12.  The  left  subclavian  ar- 
tery becoming  axillary,  and 
brachial  in  its  course,  like 
the  artery  of  the  opposite 

side.  13.  The  trunk  of  the  pulmonary  artery  connected  to  the  concavity  of  the 
arch  of  the  aorta  by  a  fibrous  cord,  the  remains  of  the  ductus  arteriosus.  14. 
The  left  pulmonary  artery.  15.  The  right  pulmonary  artery.  16.  The  trachea. 
17.  The  right  bronchus.  18.  The  left  bronchus.  19,19.  The  pulmonary  veins. 
17,  15,  and  19,  on  the  right  side;  and  14,  18,  and  19,  on  the  left,  constitute  the 
roots  of  the  corresponding  lungs,  and  the  relative  position  of  these  vessels  is 
carefully  preserved.  20.  Bronchial  arteries.  21,  21.  Intercostal  arteries,  the 
branches  from  the  front  of  the  aorta  above  and  below  the  number  3  are  pericar- 
diac  and  oesophageal  branches. 

The  left  pulmonary  artery,  shorter  and  smaller  than  the  right, 
crosses  the  descending  aorta  and  left  bronchus  to  the  root  of  the 
left  lung,  where  it  divides  into  two  branches  for  the  two  lobes. 

AORTA. — The  aorta,  the  great  arterial  trunk  of  the  body,  arises 
from  the  left  ventricle  at  the  middle  of  the  root  of  the  heart.  It 
ascends  at  first  forwards  and  to  the  right,  next  curves  backwards 
28 


326  THE   DISSECTOR. 

and  to  the  left,  and  then  descends  on  the  left  side  of  the  vertebral 
column  to  the  fourth  lumbar  vertebra.  The  aorta  within  the 
thorax  is  therefore  divided  into  the  arch  and  thoracic  aorta.  At 
its  commencement  the  vessel  presents  three  dilatations,  the  sinus 
aortici,  which  correspond  with  the  spaces  occupied  by  the  three 
semilunar  valves. 

The  arch  of  the  aorta,  commencing  at  a  point  corresponding 
with  the  articulation  of  the  cartilage  of  the  fourth  rib  with  the 
sternum  on  the  left  side,  crosses  behind  and  near  the  sternum  to 
a  point  corresponding  with  the  upper  border  of  the  articulation 
of  the  second  rib  with  the  sternum  on  the  right  side.  It  then 
curves  backwards  and  to  the  left,  and  descends  to  the  left  side  of 
the  body  of  the  third  dorsal  vertebra,  and  at  the  lower  border  of 
the  latter  vertebra  becomes  the  thoracic  aorta. 

The  first  or  ascending  portion  of  the  arch,  a  little  more  than 
two  inches  in  length,  is  almost  wholly  contained  within  the  peri- 
cardium. It  is  crossed  in  front  by  the  pulmonary  artery  :  on  its 
left  side  it  has  the  left  auricle  and  pulmonary  artery  ;  on  its  right 
the  right  auricle  and  superior  vena  cava ;  and  behind  the  right 
pulmonary  artery  and  veins. 

The  second  or  transverse  portion  of  the  arch  is  crossed  in  front 
by  the  left  phrenic  nerve,  left  nervus  superficialis  cordis,  left  in- 
ferior cardiac  of  the  pneumogastric,  and  left  pneumogastric  nerve. 
Behind  it  is  in  relation  with  the  trachea,  oesophagus,  thoracic 
duct,  the  nerves  to  the  deep  cardiac  plexus,  and  the  left  recurrent 
nerve.  Above  it  gives  off  the  arteria  innominata,  left  carotid 
and  left  subclavian  artery,  and  supports  the  left  vena  innominata ; 
and  below  is  in  relation  with  the  superficial  cardiac  plexus,  the  bi- 
furcation of  the  pulmonary  artery,  cord  of  the  ductus  arteriosus, 
left  bronchus,  and  left  recurrent  nerve. 

The  third  or  descending  portion  of  the  arch  lies  against  the 
third  dorsal  vertebra,  and  is  partially  covered  by  the  left  pleura. 

The  ARTERIA  INNOMINATA,  the  first  and  largest  branch  given 
off  by  the  arch  of  the  aorta,  is  an  inch  and  a  half  in  length.  It 
ascends  obliquely  to  the  right  sterno-clavicular  articulation,  where 
it  divides  into  the  right  carotid  and  right  subolavian  artery. 

It  is  in  relation  in  front  with  the  left  innominata,  the  sternum, 
and  origin  of  the  sterno-hyoid  and  sterno-thyroid  muscles.  Be- 
hind it  has  at  first  the  trachea,  and  then  the  right  pneumogastric 
nerve.  To  the  right  it  is  in  relation  with  the  right  vena  innomi- 
nata and  pleura ;  and  on  the  left  with  the  left  common  carotid 
artery,  and  the  remains  of  the  thymus  gland. 

The  arteria  innominata  usually  gives  off  no  branch  ;  but  some- 
times a  small  vessel  proceeds  from  it  which  ascends  upon  the 
front  of  the  trachea  to  the  thyroid  gland.  This  is  the  middle 
thyroid  artery  of  Harrison,  the  thyroidea  ima  of  Neubauer. 


VENE  INNOMINATE.  327 

The  LEFT  COMMON  CAROTID  ARTERY,  the  second  branch  from 
the  arch  of  the  aorta,  ascends  obliquely  to  the  left  sterno-clavicu- 
lar  articulation,  and  thence  passes  onwards  to  the  side  of  the  neck. 

It  is  in  relation  in  front  with  the  left  vena  innominata,  which 
crosses  it  near  its  origin  ;  the  remains  of  the  thymus  gland,  and 
the  origins  of  the  sterno-hyoid  and  sterno-thyroid  muscles.  Be- 
hind, it  rests  in  succession  on  the  trachea,  oesophagus,  and  tho- 
racic duct.  To  its  inner  side  is  the  arteria  innominata ;  and  ex- 
ternally the  left  pneumogastric  nerve  and  pleura. 

The  LEFT  SUBCLAVIAN  ARTERY,  the  third  branch  given  off  by 
the  arch  of  the  aorta,  ascends  perpendicularly  to  the  inner  border 
of  the  first  rib,  where  it  turns  outwards  over  the  rib  and  behind 
the  scalenus  anticus  muscle.  In  consequence  of  the  antero-poste- 
rior  direction  of  the  arch  of  the  aorta,  the  left  subclavian  artery 
rests  on  the  vertebral  column  and  longus  colli  muscle.  In  front 
it  has  the  pleura,  the  pneumogastric  and  phrenic  nerve ;  and  to 
its  inner  side  the  trachea,  oesophagus,  and  thoracic  duct. 

SUPERIOR  VENA  CAVA. — This  large  vein,  about  three  inches 
in  length,  is  formed  by  the  union  of  the  two  venae  innominatae. 
It  commences  immediately  to  the  right  of  the  arch  of  the  aorta ; 
at  about  its  middle  becomes  inclosed  in  the  pericardium;  and 
terminates  in  the  upper  part  of  the  right  auricle. 

It  is  in  relation  in  front  with  the  pericardium  ;  behind  with  the 
right  pulmonary  artery;  to  its  inner  side  with  the  ascending 
aorta ;  and  externally  with  the  pleura  and  right  phrenic  nerve. 

In  the  upper  half  of  its  course  the  superior  vena  cava  receives 
several  small  veins  from  the  mediastinum,  and  just  before  its  en- 
trance into  the  pericardium  it  is  joined  from  behind  by  the  great 
azy^os  vein. 

The  VENE  INNOMINATE  are  formed  by  the  union  of  the  inter- 
nal jugular  and  subclavian  vein  at  each  side. 

The  right  vena  innominata,  about  an  inch  and  a  quarter  in 
length,  descends  almost  vertically  by  the  side  of  the  arteria  inno- 
minata to  unite  with  its  fellow  of  the  opposite  side  in  the  forma- 
tion of  the  superior  vena  cava.  It  is  in  relation  by  its  outer  side 
with  the  pleura  and  right  phrenic  nerve.  This  vein  receives  at 
its  origin  the  trunk  of  the  ductus  lymphaticus  dexter,  which  opens 
into  it  from  behind  ;  and  in  its  course  it  is  joined  by  the  right 
vertebral,  right  inferior  thyroid,  and  right  internal  mammary  vein. 

The  left  vena  innominata,  considerably  longer  than  the  right, 
crosses  obliquely  the  three  great  arteries  arising  from  the  arch  of 
the  aorta  to  its  junction  with  the  right  vena  innominata.  It  is 
in  relation  in  front  with  the  left  sterno-clavicular  articulation, 
and  the  remains  of  the  thymus  gland,  which  separate  it  from  the 
sternum.  BeJiind,  it  has  the  upper  border  of  the  arch  of  the 


328  THE   DISSECTOR. 

aorta,  the  large  arteries  arising  from  it,  and  the  nerves  which 
pass  in  front  of  the  arch. 

The  veins  opening  into  the  left  vena  innominata  are  the  left 
vertebral,  left  inferior  thyroid,  left  mammary,  superior  intercostal, 
and  several  small  veins  from  the  anterior  mediastinum.  At  its 
origin  it  receives  the  thoracic  duct,  which  opens  into  it  from  be- 
hind. 

INFERIOR  YENA  CAVA. — The  inferior  vena  cava,  the  large 
trunk  from  the  lower  half  of  the  body,  after  passing  through  the 
tendinous  portion  of  the  diaphragm,  opens  immediately  into  the 
posterior  part  of  the  right  auricle.  It  receives  no  branches 
within  the  thorax. 

PULMONARY  VEINS. — The  pulmonary  veins  returning  the  pure 
blood  from  the  lungs  to  the  left  auricle  lie  in  front  of  the  other 
vessels  in  the  roots  of  the  lungs.  There  are  two  on  each  side, 
those  of  the  left  lung  being  the  veins  of  its  two  lobes;  while  on 
the  right  side  the  veins  of  the  superior  and  middle  lobe  are  united 
into  a  single  trunk.  The  right  pulmonary  veins  are  longer  than 
the  left,  and  pass  behind  the  right  auricle.  The  left  pulmonary 
veins  pass  in  front  of  the  descending  aorta. 

NERVES  OF  THE  THORAX. 

The  nerves  found  in  the  thorax  are  the  phrenic,  pneumogastric, 
and  sympathetic.  The  first  of  these  merely  pass  through  the 
thorax  in  their  way  to  the  diaphragm  :  they  have  been  already 
described,  page  307.  The  pneumogastric  and  sympathetic  sup- 
ply the  viscera  of  the  thorax  in  their  course  through  its  cavity. 

The  PNEUMOGASTRIC  NERVE,  the  largest  of  the  three  nerves  of 
the  eighth  pair,  after  descending  the  neck  in  the  sheath  of  the 
carotid  vessels,  enters  the  chest,  and,  passing  backwards  and 
inwards  behind  the  root  of  the  lungs,  reaches  the  oesophagus, 
along  which  it  takes  its  course  to  the  stomach.  As  the  two 
nerves  of  opposite  sides  of  the  chest  differ  in  their  course,  it 
becomes  necessary  to  examine  each  separately. 

The  right  nerve  enters  the  chest  after  passing  between  the 
subclavian  artery  and  vein  ;  it  then  passes  inwards  and  backwards 
by  the  side  of  the  trachea  to  the  posterior  aspect  of  the  root  of 
the  lungs,  where  it  forms  the  posterior  pulmonary  plexus.  From 
the  root  of  the  lungs  it  proceeds  as  a  double  cord  to  the  oesopha- 
gus, and  takes  its  course  along  the  posterior  aspect  of  the  oesopha- 
gus to  the  corresponding  aspect  of  the  stomach,  to  which  it  is 
distributed.  At  the  lower  part  of  the  oesophagus  the  two  cords 
reunite. 

The  left  nerve  enters  the  chest  between  the  left  common  caro- 
tid and  subclavian  artery,  and  behind  the  left  vena  iniiominata. 


SYMPATHETIC   NERVE.  329 

It  crosses  the  arch  of  the  aorta,  around  which  the  recurrent 
takes  its  course,  and  passes  backwards  to  the  posterior  aspect  of 
the  root  of  the  lungs,  where,  like  the  right,  it  forms  the  posterior 
pulmonary  plexus.  From  the  root  of  the  lung  it  passes  by  one 
or  two  cords  to  the  anterior  aspect  of  the  oesophagus,  along 
which  it  takes  its  course  to  the  corresponding  aspect  of  the 
stomach. 

The  branches  of  the  pneumogastric  nerves  within  the  thorax 
are  the  recurrent,  or  inferior  laryngeal,  cardiac,  pulmonary  ante- 
rior and  posterior,  and  cesophageaL 

The  recurrent  laryngeal  nerve  curves  around  the  subclavian 
artery  on  the  right  side  and  the  arch  of  the  aorta  on  the  left,  and 
ascends  in  the  groove  between  the  trachea  and  oesophagus  to  the 
larynx.  As  it  curves  around  its  respective  artery,  the  nerve  gives 
off  one  or  two  cardiac  branches  to  the  deep  cardiac  plexus. 

The  cardiac  branches  are  the  inferior  cardiac  given  off  from 
the  pneumogastric  just  as  that  nerve  is  about  to  enter  the  chest ; 
and  some  cardiac  branches  given  off  within  the  thorax. 

The  inferior  cardiac  branch  of  the  right  side  passes  down  by 
the  side  of  the  arteria  innominata  to  the  deep  cardiac  plexus,  and 
joins  one  of  the  cardiac  branches  of  the  sympathetic.  The  left 
inferior  cardiac  branch  has  been  already  described  (page  314) ; 
it  takes  its  course  in  front  of  the  arch  of  the  aorta  to  the  superfi- 
cial cardiac  plexus. 

The  cardiac  branches,  given  off  within  the  thorax,  are  several 
small  nerves  to  the  deep  cardiac  plexus.  On  the  right  side  they 
proceed  from  the  trunk  of  the  nerve ;  on  the  left,  from  the  recur- 
rent laryngeal. 

The  anterior  pulmonary  are  two  or  three  small  branches  which 
pass  forwards  to  the  anterior  aspect  of  the  root  of  the  lungs,  and 
form,  by  their  communications  with  filaments  from  the  cardiac 
plexuses,  the  anterior  pulmonary  plexus. 

The  posterior  pulmonary  branches,  larger  and  more  numerous 
than  the  anterior,  proceed  from  the  nerve  where  it  is  flattened 
and  split  into  several  cords.  These  branches  are  joined  by  fila- 
ments from  the  third  and  fourth  thoracic  ganglia  of  the  sympa- 
thetic, and  form  the  posterior  pulmonary  plexus. 

(J'^ophageal  branches  are  given  off  by  the  pneumogastric  nerves 
above  the  root  of  the  lungs :  below  that  point,  the  trunks  of  the 
nerves,  divided  into  several  cords,  form  a  plexus  around  the 
oesophagus,  the  right  and  left  nerves  communicating  with  each 
other.  This  plexus  accompanies  the  oesophagus  to  the  stomach, 
and  is  the  oesophageal  plexus  (plexus  guise). 

SYMPATHETIC  NERVE. — The  sympathetic  nerve  within  the  tho- 
rax consists  of  two  portions  ;  one,  prevertebral,  composed  of 
nerves  descending  from  the  neck,  and  forming  the  superficial  and 

28* 


330        .  THE   DISSECTOR. 

deep  cardiac  plexus ;  the  other,  the  vertebral  portion,  being  the 
trunk  of  the  gan'gliated  cord,  situated  on  the  heads  of  the  ribs  by 
the  side  of  the  vertebral  column. 

The  superficial  cardiac  plexus,  situated  beneath  the  arch  of  the  aorta, 
has  been  already  examined  (p.  323).  To  see  the  deep  cardiac  plexus,  it 
is  necessary  to  draw  aside  the  arch  of  the  aorta,  behind  which  it  lies. 
This  may  be  best  effected  by  dividing  the  aorta  through  each  extremity 
of  the  transverse  portion  of  the  arch,  cutting  through  the  ligament  of  the 
ductus  arteriosus,  and  drawing  the  several  parts  of  the  vessel,  with  its 
large  branches,  upwards.  By  the  removal  of  some  cellular  tissue  and 
lymphatic  glands,  the  deep  cardiac  plexus  and  lower  part  of  the  trachea, 
with  its  bifurcation,  will  be  brought  into  view. 

The  deep  or  great  cardiac  plexus  is  situated  on  the  bifurcation 
of  the  trachea  above  the  right  pulmonary  artery,  and  behind  the 
transverse  portion  of  the  arch  of  the  aorta.  It  receives,  on  the 
right  side,  the  three  cardiac  nerves  of  the  sympathetic  of  the  same 
side,  and  the  cardiac  branches  of  the  right  pneumogastric  and 
right  recurrent  nerve.  On  the  left  side  it  receives  the  middle  and 
inferior  cardiac  nerves  of  the  sympathetic  of  the  left  side;  the 
cardiac  branches  of  the  left  pneumogastric  (excepting  the  infe- 
rior), and  several  cardiac  branches  from  the  left  recurrent  nerve. 
In  other  words,  it  receives  all  the  cardiac  filaments  of  the  sympa- 
thetic, pneumogastric,  and  recurrent  nerves,  with  the  exception 
of  the  left  superior  cardiac  of  the  sympathetic  (nervus  superficialis 
cordis)  and  the  inferior  cervical  cardiac  of  the  left  pneumogastric, 
these  two  nerves  being  destined  to  the  superficial  cardiac  plexus. 

The  cardiac  nerves  being  situated  on  a  plane  posterior  to  that 
of  the  arteries,  are  found  in  that  situation  at  their  entrance  into 
the  chest.  The  nerves  of  the  right  side  pass  for  the  most  part 
behind  (but  sometimes  in  front  of)  the  subclavian  artery  ;  those 
of  the  left  side  enter  the  chest  between  the  carotid  and  subclavian 
artery.  The  nervus  superficialis  cordis  of  the  right  side  runs  by  the 
side  of  the  arteria  innominata ;  that  of  the  left  side  takes  the  left 
common  carotid  for  its  guide ;  while  the  other  nerves,  in  their 
course  to  the  deep  plexus,  pass  inwards  to  the  side  of  the  trachea. 

The  branches  of  the  deep  cardiac  plexus,  proceeding  from  its 
right  and  left  division,  pass  downwards  to  join  the  coronary 
arteries,  and  outwards  to  the  pulmonary  plexuses.  From  the 
right  division  of  the  plexus  the  branches  proceed  before  and 
behind  the  right  pulmonary  artery.  Those  which  pass  in  front 
descend  upon  the  trunk  of  the  pulmonary  to  the  left  coronary 
artery,  and  constitute  the  anterior  coronary  plexus  ;  those  which 
pass  behind  the  right  pulmonary  artery  are  distributed  to  the 
right  auricle ;  a  third  set  of  filaments,  proceeding  from  the  right 
division  of  the  deep  cardiac  plexus  follow  the  course  of  the  right 
pulmonary  artery  to  the  anterior  pulmonary  plexus. 

From  the  left  division  of  the  plexus  branches  proceed  beneath 


INTERCOSTAL   NERVES.  331 

the  arch  of  the  aorta  immediately  to  the  right  of  the  ligament  of 
the  ductus  arteriosnsto  join  the  superficial  cardiac  plexus;  others 
pass  outwards  with  the  pulmonary  artery  to  the  pulmonary  plexus ; 
a  few  descend  to  the  left  auricle ;  but  the  chief  bulk  pass  on  to  the 
right  coronary  artery  and  form  the  posterior  coronary  plexus. 

The  vertebral  portion  of  the  sympathetic  nerve  is  the  trunk  of 
the  sympathetic  in  its  course  through  the  cavity  of  the  thorax. 
It  lies  by  the  side  of  the  vertebral  column  upon  the  heads  of  the 
ribs  and  intercostal  spaces ;  but  at  its  lowest  part  comes  into  re- 
lation with  the  sides  of  the  bodies  of  the  last  two  dorsal  vertebra. 

To  see  the  nerve  distinctly,  the  pleura  should  be  stripped  from  the  sides 
of  the  vertebral  column,  and  any  fat  which  may  impede  the  view  of  the 
nerve  and  its  branches  removed. 

The  thoracic  portion  of  the  great  sympathetic  nerve  consists 
of  twelve  ganglia  with  their  connecting  cords.  The  ganglia  are 
flat,  of  a  pearly  hue,  and  somewhat  triangular  shape ;  and  each 
ganglion  overlies  the  head  of  the  corresponding  rib.  The  first 
two  ganglia  are  larger  than  the  rest. 

The  branches  of  the  thoracic  ganglia  are  external,  or  commu- 
nicating, two  or  three  in  number,  to  communicate  with  each  inter- 
costal nerve ;  and  internal  or  visceral. 

The  visceral  branches,  arising  from  the  five  or  six  upper  gan- 
glia, are  of  small  size,  and  are  distributed  to  the  aorta,  esophagus, 
vertebral  column,  and  lungs.  The  branches  to  the  lungs  proceed 
from  the  third  and  fourth  ganglia,  and  go  to  join  the  posterior 
pulmonary  plexus.  The  visceral  branches  of  the  six  lower  ganglia 
unite  to  form  the  three  splanchnic  nerves. 

The  great  splanchnic  nerve  proceeds  from  the  sixth  dorsal 
ganglion,  and  receiving  the  branches  of  the  seventh,  eighth,  ninth, 
and  tenth,  passes  downwards  upon  the  front  of  the  vertebral  col- 
umn, and  piercing  the  crus  of  the  diaphragm,  terminates  in  the 
semilunar  ganglion. 

The  lesser  splanchnic  nerve  is  formed  by  filaments  which  issue 
from  the  tenth  and  eleventh  ganglia ;  it  pierces  the  crus  of  the 
diaphragm,  and  joins  the  solar  plexus  near  the  middle  line. 

The  third  or  renal  splanchnic  nerve  proceeds  from  the  last 
thoracic  ganglion,  and,  piercing  the  diaphragm,  terminates  in 
the  renal  plexus.  When  absent,  the  place  of  this  nerve  is  sup- 
plied by  the  lesser  splanchnic. 

The  process  by  which  the  sympathetic  nerve  was  brought  into  view — 
namely,  that  of  stripping  off  the  pleura — exposes  also  the  intercostal 
spaces,  with  the  intercostal  nerves  and  vessels.  The  relation  of  these 
parts  may  now  be  examined,  and  one  of  the  intercostal  nerves  traced 
through  its  course. 

The  INTERCOSTAL  NERVES  are  twelve  in  number  on  each  side 
of  the  thorax ;  the  eleven  superior  nerves  lie  in  the  intercostal 


332  THE  DISSECTOR. 

spaces,  the  twelfth  below  the  lower  border  of  the  last  rib.  Each 
nerve  lies  upon  an  external  intercostal  muscle,  but  soon  gets  under 
cover  of  the  internal  intercostal,  and  then  passes  between  the  two 
planes  of  muscle  to  the  front  part  of  the  chest.  Near  its  origin  the 
nerve  receives  two  or  three  filaments  from  the  neighboring  ganglion 
of  the  sympathetic  ;  in  its  course  it  gives  twigs  to  the  intercostal 
muscles,  and  at  the  middle  of  the  arch  of  the  rib  sends  off  the 
lateral  cutaneous  branch. 

The  first  intercostal  nerve  ascends  from  the  intercostal  space, 
and  crosses  the  neck  of  the  first  rib  to  join  the  brachial  plexus. 
It  sends  off  a  small  intercostal  branch,  which  takes  the  course  of 
the  other  nerves  to  the  front  of  the  chest;  but  the  latter  gives  no 
lateral  cutaneous  branch. 

The  second  intercostal  nerve  is  remarkable  for  the  large  size  of 
its  lateral  cutaneous  nerve,  the  intercosto-humeral. 

The  six  inferior  intercostal  nerves  at  the  termination  of  the  in- 
tercostal spaces  continue  their  course  to  the  middle  line  of  the 
body  between  the  abdominal  muscles. 

CONTENTS  OP  THE  POSTERIOR  MEDIASTINUM. 

Returning  now  to  the  middle  line,  the  student  may  examine 
and  dissect  the  parts  which  are  usually  enumerated  as  being  con- 
tained in  the  posterior  mediastinum.  They  are  the  oesophagus, 
aorta,  venae  azygos,  and  thoracic  duct.  In  front  of  them,  at  the 
upper  part  of  the  chest,  and  for  the  first  time  fully  brought  into 
view,  is  the  trachea. 

TRACHEA. — The  trachea  or  windpipe  extends  from  the  larynx 
to  the  lungs ;  it  lies  over  the  vertebral  column,  and  is  about  four 
inches  in  length.  Its  commencement  corresponds  in  position 
with  the  fifth  cervical  vertebra,  and  its  termination,  where  it 
divides  into  the  two  bronchi  with  the  third  dorsal  vertebra.  It 
is  cylindrical  for  three-fourths  of  its  circumference,  but  flattened 
behind,  where  it  is  in  relation  with  the  oesophagus.  The  bronchi 
have  the  same  shape  as  the  trachea,  but  the  bronchial  tubes  into 
which  the  bronchi  divide  are  perfectly  cylindrical.  The  right 
bronchus,  about  an  inch  in  length,  is  horizontal  in  direction, 
occupies  the  upper  part  of  the  root  of  the  lung  ;  and  divides  into 
three  bronchial  tubes  for  the  three  lobes  of  the  lung.  The  left 
bronchus,  two  inches  in  length,  is  oblique  in  direction,  smaller 
than  the  right,  and  descends  to  the  middle  of  the  root  of  the 
lung.  It  divides  into  two  bronchial  tubes  for  the  two  lobes  of 
the  lung. 

In  structure  the  trachea  and  bronchi  are  composed  of  fibre-cartilaginous 
rings,  connected  by  a  fibrous  membrane  ;  they  have  also  entering  into 
their  composition,  muscular  fibres,  a  coat  of  elastic  tissue,  mucous  mem- 
brane and  mucous  glands. 


(ESOPHAGUS.  333 

The  fibro-cartilaginous  rings  are  from  fifteen  to  twenty  in  number,  and 
extend  for  two-thirds  around  the  cylinder  of  the  trachea.  The  lowest 
ring  differs  in  shape  from  the  rest,  being  prolonged  to  a  V-shaped  point 
between  the  bronchi  at  the  bifurcation  of  the  trachea. 

The  fibrous  membrane  incloses  the  rings  completely,  and  forms  a  dis- 
tinct layer  over  their  outer  surface. 

The  muscular  fibres  form  a  thin  stratum,  extending  transversely  be- 
tween the  cartilaginous  rings  behind. 

The  elastic  coat  is  composed  of  fibres  of  elastic  tissue  disposed  longi- 
tudinally. Where  they  invest  the  cartilages  they  form  a  thin  layer,  but 
behind,  in  the  flat  part  of  the  tube  between  the  cartilages,  the  fibres 
are  gathered  into  strong  fasciculi. 

The  mucous  membrane  is  closely  adherent  to  the  elastic  coat,  and  is 
continuous  above  with  the  lining  of  the  larynx,  and  below  with  that  of 
the  bronchial  tubes. 

The  mucous  glands  are  small  ovoid  bodies  situated  externally  to  the 
fibrous  membrane,  and  between  that  membrane  and  the  muscular  layer 
behind,  and  in  the  substance  of  the  fibrous  membrane  between  the 
rings.  Their  ducts  open  upon  the  mucous  membrane. 

(ESOPHAGUS. — The  oesophagus  commences  in  the  neck  oppo- 
site the  fifth  cervical  vertebra,  and  pursues  a  slightly  flexuous 
course  through  the  posterior  mediastinum  to  the  cesophageal 
opening  of  the  diaphragm.  Through  the  neck  it  inclines  slightly 
to  the  left  side  ;  having  entered  the  thorax,  it  bends  a  little  to 
the  right,  and  reaches  the  midline  of  the  vertebral  column  oppo- 
site the  fifth  dorsal  vertebra  ;  it  then  turns  again  to  the  left,  gets 
in  front  of  the  aorta,  and  passes  through  the  cesophageal  opening 
in  front  of  that  vessel. 

In  the  upper  part  of  the  thorax  the  oesophagus  lies  behind  the 
trachea,  projecting  a  little  on  its  left  side  ;  it  then  passes  behind 
the  arch  of  the  aorta,  the  left  bronchus,  and  the  pericardium. 
Laterally,  it  is  in  relation  with  the  pleura ;  on  the  right  with 
the  great  vena  azygos,  and  on  the  left  with  the  aorta.  It  rests  in 
its  course  downwards  on  the  longus  colli  muscles,  the  right  inter- 
qostal  arteries,  thoracic  duct,  and  lower  down  on  the  aorta. 

In  structure  the  oesophagus  is  composed  of  three  coats,  muscular,  cellu- 
lar, and  mucous. 

The  muscular  coat  consists  of  two  layers  of  fibres,  longitudinal  and  cir- 
cular. The  longitudinal  fibres  are  connected  above  with  the  cricoid  car- 
tilage and  muscular  structure  of  the  pharynx,  and  form  a  thick  stratum 
around  the  tube  ;  inferiorly  they  expand  upon  the  stomach.  The  circular 
fibres  forming  the  internal  layer  are  continuous  above  with  the  muscular 
structure  of  the  pharynx,  and  are  also  attached  to  the  cricoid  cartilage ; 
inferiorly  they  enlarge  and  surround  the  stomach. 

The  muscular  fibres  of  the  upper  part  of  the  oesophagus  are  of  the 
striated  kind,  the  muscle  of  animal  life  ;  and  those  of  the  lower  part  the 
non-striated  kind,  the  muscle  of  organic  life. 

The  cellular  coat  is  a  moderately  thick  layer  of  cellular  tissue,  which 
connects  together  the  muscular  and  the  mucous  coat ;  it  is  loosely  adhe- 
rent to  the  former,  but  closely  to  the  latter. 

The  mucous  coat  is  thick,  and  presents  upon  its  surface  a  few  minute 


334  THE   DISSECTOR. 

and  scattered  papillae.  It  is  arranged  in  longitudinal  plicce,  and  is 
covered  by  a  thick  whitish  epithelium  of  the  squamous  or  tessellated  kind. 
It  is  but  loosely  connected  with  the  muscular  coat. 

The  mucous  glands  of  the  oesophagus  (oesophageal  glands)  are  most 
abundant  at  the  lower  part  of  the  tube  ;  they  are  small  lobulated  bodies, 
situated  in  the  cellular  coat,  and  opening  on  the  surface  of  the  mucous 
membrane  by  means  of  long  excretory  tubes. 

THORACIC  AORTA. — The  thoracic  aorta,  commencing  at  the 
lower  border  and  left  side  of  the  third  dorsal  vertebra,  curves 
gently  towards  the  right  as  it  descends,  and  as  it  passes  through 
the  aortic  opening  of  the  diaphragm  lies  upon  the  middle  line  of 
the  vertebral  column. 

The  branches  of  the  thoracic  aorta  are,  the  pericardiac,  bron- 
chial, oesophageal,  posterior  mediastinal,  and  intercostal. 

The  bronchial  arteries,  generally  three  in  number,  one  for  the 
right  lung  and  two  for  the  left,  vary  both  in  size  and  origin  ;  the 
right  often  proceeding  from  a  short  trunk  common  to  it  and  one 
of  the  left  bronchial  branches,  or  from  the  first  aortic  intercostal. 
They  take  their  course  to  the  back  of  the  root  of  the  lung,  and 
accompany  the  ramifications  of  the  bronchial  tubes  through  its 
substance.  They  give  twigs  also  to  the  bronchial  glands,  oeso- 
phagus, and  pericardium. 

The  cesophageal  arteries,  four  or  five  in  number,  arise  from  the 
anterior  part  of  the  aorta,  and  are  distributed  to  the  oesophagus, 
establishing  a  chain  of  anastomoses  along  that  tube  :  the  supe- 
rior inosculate  with  the  bronchial  arteries,  and  with  oesophageal 
branches  of  the  inferior  thyroid  arteries ;  and  the  inferior  with 
similar  branches  of  the  phrenic  and  gastric  arteries. 

The  posterior  mediastinal  arteries  are  small  twigs  distributed 
to  the  lymphatic  glands  and  cellular  tissue  of  the  posterior  medi- 
astinum. 

The  intercostal  arteries,  nine  in  number  on  each  side,  the  two 
superior  spaces  being  supplied  by  the  superior  intercostal  artery, 
a  branch  of  the  subclavian,  arise  from  the  posterior  part  of  the 
aorta.  The  right  intercostals  are  longer  than  the  left  on  account 
of  the  position  of  the  aorta.  They  ascend  somewhat  obliquely 
from  their  origin,  and  cross  the  vertebral  column  behind  the 
thoracic  duct,  vena  azygos  major,  and  sympathetic  nerve  to  the 
intercostal  spaces  ;  the  left  passing  beneath  the  superior  inter- 
costal vein,  vena  azygos  minor,  and  sympathetic. 

In  the  intercostal  space,  the  artery  comes  into  relation  with 
the  vein  and  nerve,  the  former  being  above,  and  the  latter  imme- 
diately below  it.  It  is  covered  in  by  a  thin  fascia,  continued  from 
the  free  edge  of  the  internal  intercostal  muscle  to  the  vertebra ; 
and  rests  upon  the  external  intercostal  muscle. 

On  first  entering  the  intercostal  space,  the  intercostal  artery 
gives  off  a  dorsal  branchf  which  passes  back  close  to  the  vertebrae 


VENA  AZYGOS.  335 

and  between  their  transverse  processes,  to  be  distributed  to  the 
muscles  and  integument  of  the  back,  and  by  means  of  a  small 
spinal  twig  to  the  interior  of  the  vertebral  column.  The  artery 
next  takes  its  course  along  the  middle  of  the  intercostal  space, 
and  gradually  ascends  to  the  lower  border  of  the  rib  above,  with 
which  it  comes  into  relation  at  about  its  angle ;  the  artery  then 
follows  the  lower  border  of  the  rib,  lying  between  the  two  planes 
of  intercostal  muscles  to  the  front  of  the  chest,  where  it  inoscu- 
lates with  the  corresponding  anterior  intercostal  branch  of  the 
internal  mammary  artery. 

Besides  the  dorsal  branch,  and  several  small  muscular  branches, 
the  intercostal  artery,  at  about  the  middle  of  its  course,  gives  off 
a  large  branch,  which  runs  along  the  upper  border  of  the  rib 
below,  to  the  front  part  of  the  chest,  and  inosculates  with  an 
anterior  intercostal  branch  of  the  internal  mammary. 

The  upper  pair  of  aortic  intercostal  arteries  inosculate  with  the 
superior  intercostals  of  the  subclavians  ;  the  lower  pair  anasto- 
mose with  the  lumbar  and  epigastric  arteries  in  the  parietes  of 
the  abdomen. 

SUPERIOR  INTERCOSTAL  ARTERIES. — Supplying  the  upper  two 
intercostal  spaces  on  each  side  is  the  superior  intercostal  artery. 
It  arises  from  the  subclavian  artery,  and  descends  over  the  necks 
of  the  first  and  second  ribs  externally  to  the  sympathetic  nerve, 
and  inosculates  with  the  first  aortic  intercostal.  It  sends  off 
branches  to  the  first  and  second  intercostal  spaces,  and  dorsal 
branches  to  the  muscles  and  integument  of  the  back. 

VEINS  OF  TUB  POSTERIOR  MEDIASTINUM. — The  venae  azygos 
major  and  minor  and  left  superior  intercostal  vein  constitute  a 
small  prevertebral  system  of  veins,  interposed  between  the  supe- 
rior and  inferior  vena  cava,  and  communicating  with  both. 

The  VENA  AZYGOS  MAJOR  commences  in  the  lumbar  region  by 
a  communication  with  the  right  lumbar  veins.  It  passes  through 
the  aortic  opening  of  the  diaphragm,  ascends  along  the  right  side 
of  the  vertebral  column,  and  opposite  the  third  dorsal  vertebra 
arches  forward  over  the  root  of  the  right  lung,  to  terminate  in 
the  superior  vena  cava  at  its  entrance  into  the  pericardium.  In 
its  course  its  lies  superficially  to  the  right  intercostal  arteries, 
having  the  thoracic  duct  on  its  left  and  the  pleura  on  its  right 
side.  It  receives  all  the  intercostal  veins  of  the  right  side  (with 
the  exception  of  those  of  the  first  and  second  spaces),  the  vena 
azygos  minor,  and  the  right  bronchial  vein. 

The  VENA  AZYGOS  MINOR  commences  in  the  lumbar  region  by 
a  communication  with  one  of  the  left  lumbar  veins,  or  with  the 
left  renal  :  it  enters  the  chest  through  the  aortic  opening,  or, 
more  frequently,  through  the  crus  of  the  diaphragm,  and  ascends 
the  left  side  of  the  vertebral  column  to  the  fifth  or  sixth  vertebra, 


336 


THE   DISSECTOE. 


Fig.  104. 


L 


which  it  crosses  to  terminate  in  the  vena  azygos  major.  It  re- 
ceives the  six  or  seven  lower  intercostal  veins  of  the  left  side. 
The  azygos  veins  have  no  valves. 

The  right  superior  intercostal  vein  receives  the  veins  of  the  first 
and  second  intercostal  spaces,  and  opens  into  the  subclavian  vein 
of  the  same  side. 

The  left  superior  intercostal  vein  receives  the  veins  from  all 
the  intercostal  spaces  (five  or  six)  of 
the  left  side  above  the  vena  azygos  mi- 
nor and  the  left  bronchial  vein.  It 
communicates  below  with  the  vena 
azygos  minor,  and  crosses  the  arch  of 
the  aorta  to  terminate  in  the  left  vena 
innominata. 

THORACIC  DUCT. — The  thoracic  duct 
is  the  great  trunk  of  the  lymphatic  and 
chylous  system.  It  commences  in  the 
abdomen  on  the  second  lumbar  verte- 
bra by  an  enlargement  of  considerable 
size  termed  receptaculum  cliyli  ;  enters 
the  chest  through  the  aortic  opening, 
ascends  upon  the  vertebral  column  be- 
tween the  aorta  and  vena  azygos  major, 
and  terminates  at  the  root  of  the  neck 
on  the  left  side  by  opening  into  the 
angle  of  junction  between  the  internal 
jugular  and  subclavian  vein.  At  the 
aortic  opening  the  thoracic  duct  lies 
close  to  the  right  crus  of  the  diaphragm, 
in  the  thorax  it  rests  upon  the  right 
intercostal  arteries,  and  opposite  the 
fourth  dorsal  vertebra  inclines  to  the 
left  side.  A  little  higher  it  passes  be- 
hind the  arch  of  the  aorta  and  reaches 
the  left  side  of  the  oesophagus  along 
which  it  takes  its  course,  lying  behind 
the  left  subclavian  artery,  to  the  root 

THE  VEINS  OF  THE  TRUNK. — 1.  The  superior  vena  cava.  2.  The  right  vena 
innominata.  3.  The  left  vena  innominata.  4.  The  internal  jugular  vein  of  the 
left  side.  5.  The  subclavian  vein  of  the  left  side.  6.  The  external  jugular  vein. 
7.  The  superior  intercostal  vein.  8.  The  great  vena  azygos,  communicating  in- 
feriorly  with  one  of  the  lumhar  veins.  9.  The  lesser  vena  azygos,  communicating 
inferiorly  with  a  lumbar  and  with  the  left  renal  vein.  10.  The  inferior  vena  cava. 
11,  11.  The  two  common  iliac  veins.  12.  The  left  external  iliac.  13.  The  internal 
iliac  vein.  34.  The  vena  sacra  media.  15,  15.  The  lumbar  veins.  16.  The 
right  spermatic  vein.  17.  The  left  renal  vein,  into  which  is  seen  opening  from 
below  the  left  spermatic  vein.  18.  The  right  renal  vein.  19.  The  hepatic 
veins. 


LYMPHATIC  GLANDS.  33T 

of  the  neck.  It  there  makes  a  hook-like  bend  from  behind  for- 
wards, to  its  termination. 

The  thoracic  duct  is  about  eighteen  or  twenty  inches  in  length, 
and  near  its  origin  as  large  as  a  goose  quill  ;  as  it  ascends  it 
diminishes  in  size,  and  near  its  termination  again  becomes  dilated. 
At  about  the  middle  of  the  thorax  it  frequently  divides  into  two 
branches,  which  soon  after  reunite ;  sometimes  it  forms  a  kind  of 
plexus  in  this  situation  ;  and  occasionally  divides  into  two  branches 
near  its  termination. 

The  thoracic  duct  within  the  thorax  receives  the  lymphatics  of 
the  left  side  of  the  chest,  and  from  the  left  side  of  its  contained 
viscera.  The  lymphatics  of  the  right  side  of  the  chest  and  right 
half  of  the  thoracic  viscera  terminate  in  a  short  trunk,  the  ductus 
lymphaticus  dexter,  situated  in  the  root  of  the  neck  of  the  right 
side,  and  terminating  in  the  junction  of  the  right  internal  jugular 
and  right  subclavian  vein. 

The  thoracic  duct  and  ductus  lymphaticus  dexter  are  both 
provided  with  valves,  and  at  their  termination  is  a  large  valve 
which  prevents  the  regurgitation  of  blood  from  the  veins. 

LYMPHATIC  GLANDS. — The  lymphatic  glands  of  the  thorax  are 
the  anterior  mediastiual,  intercostal,  cesophageal,  bronchial,  and 
cardiac. 

The  anterior  mediastinal  glands  are  situated  along  the  course 
of  the  internal  mammary  arteries  ;  they  are  six  or  seven  in  number 
on  each  side,  and  receive  the  lymphatic  vessels  from  the  anterior 
wall  of  the  chest,  the  mediastinum,  thymus  gland,  and  pericardium. 

The  intercostal  glands  are  situated  near  the  intercostal  arteries 
on  each  side  of  the  vertebral  column.  They  receive  the  lymphatics 
from  the  intercostal  spaces  and  posterior  wall  of  the  thorax. 

The  cesophageal  glands,  fifteen  or  twenty  in  number,  are  situ- 
ated in  the  course  of  the  oesophagus,  and  receive  the  lymphatics 
of  that  tube. 

The  bronchial  glands,  ten  or  twelve  in  number,  are  placed  near 
the  bifurcation  of  the  trachea  and  the  roots  of  the  lungs.  They 
receive  the  lymphatics  of  the  lungs  both  superficial  and  deep. 

The  cardiac  glands  are  three  or  four  in  number,  and  placed 
near  the  arch  of  the  aorta ;  they  receive  the  lymphatics  of  the 
heart. 

All  the  lymphatics  of  the  chest  terminate  eventually  in  the 
thoracic  duct  or  ductus  lymphaticus  dexter. 

Internal  Parietes  of  the  Thorax. — The  intercostal  muscles, 
which  are  examined,  upon  the  exterior  of  the  chest,  at  page  354, 
may  now  be  studied  from  within.  The  internal  intercostal  is 
seen  to  terminate  by  an  abrupt  border,  from  which  a  thin  aponeu- 
rosis  is  continued  onwards  over  the  intercostal  vessels  and  nerve 
to  the  side  of  the  vertebral  column. 


338  THE   DISSECTOR. 

Iii  the  dome  of  the  chest  maybe  examined  the  relative  position 
of  the  parts  which  pass  to  and  from  the  chest ;  and  in  its  floor 
the  unequally  convex  surface  of  the  diaphragm,  with  the  open- 
ings which  give  passage  to  parts  passing  to  and  from  the  ab- 
domen. 

In  the  superior  opening  of  the  thorax  will  be  seen,  from  before 
backwards,  the  sterno-hyoid  and  sterno-thyroid  muscles ;  remains 
of  the  thymus  gland ;  vense  innominatae  ;  phrenic  and  pneumo- 
gastric  nerves  ;  arteriainnominata  and  left  carotid  artery  ;  cardiac 
nerves  ;  trachea  ;  left  recurrent  nerve  ;  oesophagus ;  left  subclavian 
artery  ;  thoracic  duct ;  longus  colli  muscles  ;  superior  intercostal 
arteries  ;  first  dorsal  nerve  ;  and  sympathetic.  Besides  these  parts, 
which  are  in  the  state  of  transit,  there  is  at  each  side  the  pouch 
of  pleura  for  the  reception  of  the  summit  of  the  corresponding 
lung. 

The  apertures  in  the  floor  of  the  thorax,  and  the  parts  to  which 
they  give  passage,  are,  the  quadrilateral  opening  in  the  tendinous 
centre  of  the  diaphragm  for  the  inferior  vena  cava ;  the  elliptical 
opening  in  the  muscular  structure  of  the  diaphragm  for  the  oeso- 
phagus and  pneumogastric  nerves,  and  the  musculo-fibrous  arch 
behind  the  central  part  of  the  diaphragm,  the  aortic  opening,  for 
the  aorta,  thoracic  duct,  and  right  vena  azygos.  The  left  vena 
azygos,  sympathetic,  and  splanchnic  nerves,  pass  through  irregu- 
lar intervals  in  the  muscular  structure  of  the  crura  of  the  dia- 
phragm. 

After  completing  the  thorax,  the  student  must  turn  his  attention  to  the 
dissection  of  the  back  and  its  muscles. 


CHAPTER    VII. 

THE  UPPER  EXTREMITY. 

THE  upper  extremity  is  the  member  developed  from  the  upper 
part  of  the  thoracic  arch,  as  the  lower  extremity  is  the  member 
developed  from  the  pelvic  arch.  It  consists  of  an  apparatus  of 
bones,  joints,  muscles,  vessels,  and  nerves,  and  is  covered  by  the 
common  investments  of  the  entire  body,  viz:  the  deep  and  super- 
ficial fascia  and  the  integument. 

The  bones  of  the  upper  extremity  are  the  clavicle,  scapula, 
humerus,  radius  and  ulna,  carpal,  metacarpal,  and  phalanges. 
The  clavicle  is  the  medium  of  connection  between  the  upper  ex- 
tremity and  the  rest  of  the  skeleton  ;  it  is  the  fulcrum  of  action 


UPPER  EXTREMITY — MUSCLES.  339 

of  the  entire  limb,  and  is  prominently  characteristic  of  animals 
possessing  great  power  in  the  arms,  as  man,  the  bat,  the  mole, 
birds,  &c.  The  scapula  is  a  flat  bone,  and  affords  by  its  con- 
struction peculiar  advantages  ;  giving  origin,  by  its  extensive 
surface,  to  a  number  of  muscles,  and  being  itself  movable  on 
the  convexity  of  the  thorax.  This  is  the  bone  which  secures 
the  connection  of  the  arm  with  the  trunk,  and  provides  for  all 
the  diversity  of  movement  so  characteristic  of  the  upper  extre- 
mity, and  which  entitles  it  to  the  designation  of  an  "  universal 
joint."  The  next  bones,  the  humerus,  radius,  and  ulna,  have  for 
their  office  the  extension  of  the  limb,  for  the  purpose  of  supply- 
ing to  the  beautiful  apparatus  of  the  hand  the  advantages  which 
are  to  be  obtained  by  a  voluntary  approximation  or  extension 
from  the  body.  They  are,  therefore,  denominated  long  bones, 
and  like  all  bones  of  this  class  are  divisible  into  a  shaft,  an  upper 
and  a  lower  extremity.  The  shaft  is  more  or  less  cylindrical  and 
smooth,  whilst  the  extremities  are  projected  into  processes  which 
serve  as  levers  for  the  attachment  and  action  of  muscles.  The 
carpus  is  an  assemblage  of  small  bones  belonging  to  the  class  of 
short  bones.  They  are  all  slightly  movable  upon  each  other, 
and  bestow  pliancy  and  strength  by  means  of  the  mutual  yielding 
which  exists  between  them.  The  metacarpal  bones  and  phalanges 
are  long  bones,  of  a  length  proportionate  to  the  arm  and  to  the 
moving  powers  intended  for  their  action;  they  give  breadth  and 
extent  to  the  hand,  and  facility  in  all  the  movements  which  that 
important  organ  is  destined  to  perform. 

The  muscles  are  naturally  divided  into  groups,  which  concur 
mutually  in  certain  actions  necessary  to  the  effective  movements 
of  the  limb.  The  distribution  of  these  groups,  with  their  corre- 
sponding duties,  will  be  best  seen  in  a  tabular  analysis,  thus  :•— 

Anterior  Thoracic  Group.  Posterior  Thoracic  Group, 

Pectoralis  major.  Trapezius. 

Pectoralis  minor.  Levator  anguli  scapulae. 

Subclavius.  Rhomboideus  major. 

Serratus  magnus.  Rhomboideus  minor, 

Humeral  Group. 

Subscapularis.  Latissimus  dorsi, 

Supra-spinatus.  Pectoralis  major, 

Infra-spinatus.  Deltoid. 

Teres  minor.  Coraco-brachialis. 

Teres  major. 

Anterior  Brachial  Group.  Posterior  Brachial  Group. 

Biceps.  Triceps. 

Brachialis  anticus.  Anconeus. 


340  THE  DISSECTOR. 


FORE- ARM. 

Anterior  Group.  Posterior  Group. 

Pronator  radii  teres.  Snpinator  radii  longus. 

Pronator  radii  quadratus.  Supinator  radii  brevis. 

Flexor  carpi  radialis.  Extensor  carpi  radialis  longior. 

Flexor  carpi  ulnaris.  Extensor  carpi  radialis  brevior. 

Flexor  digitorum  sublimis.  Extensor  carpi  nlnaris. 

Flexor  digitorum  profundus.  Extensor  communis  digitornm. 

Flexor  pollicis  longus.  Extensor  minimi  digiti. 

Palmaris  longus.  Extensor  pollicis  ossis  metacarpi. 

Extensor  pollicis  primi  internodii. 

Extensor  pollicis  secundi  internodii. 

Extensor  indicis. 

HAND. 

Radial  Group.  Ulnar  Group. 

Flexor  ossis  metacarpi.  Palmaris  brevis. 

Flexor  brevis  pollicis.  Flexor  ossis  metacarpi. 

Abductor  pollicis.  Flexor  brevis  minimi  digiti. 

Adductor  pollicis.  Abductor  minimi  digiti. 

Palmar  Group. 
Lumbricales. 
Interossei  palmares. 
Interossei  dorsales. 

The  anterior  and  posterior  thoracic  groups  preserve  the  fixity 
and  steadiness  of  the  shoulder,  and  render  it  capable  of  sup- 
p'orting  heavy  weights  and  becoming  the  point  of  resistance  to 
the  actions  of  the  humeral  muscles.  They  also  move  the  scapula 
freely  on  the  chest,  and  afford  all  the  advantages  of  the  strongest 
articulation  by  bone.  The  humeral  group  carries  the  arm 
throughout  all  that  circle  of  motion  which  is  so  necessary  to  an 
universal  joint,  and  so  valuable  in  application  to  its  extensive 
uses.  The  muscles  of  the  anterior  brachial  group  are  the  flexors 
of  the  elbow,  the  perfect  flexion  of  the  joint  being  procured  by 
an  advantageous  attachment  to  both  the  radius  and  ulna.  The 
posterior  brachinl  group  is  the  antagonist  to  the  former,  and  ex- 
tends the  forearm.  Now,  it  is  fair  to  anticipate,  that  as  the  bones 
increase  in  number,  and  the  limb  is  carried  further  from  the  centre, 
the  movements  will  increase  in  proportionate  ratio.  The  move- 
ments of  the  shoulder  were  those  of  totality :  the  motions  of  the 
scapulo-humeral  joint  were  of  the  most  simple  kind,  such  as  would 
result  from  the  application  of  a  round  ball  against  a  shallow 
socket ;  those  of  the  elbow  were  in  one  direction  only,  flexion 
and  extension  ;  but  the  wrist  requires  an  apparatus  for  the  action 
of  the  powerful  twist  which  is  so  remarkable  in  that  joint.  And 
this  is  provided  for  by  two  pairs  of  the  muscles  of  the  forearm, 
the  pronators  and  supinators,  the  former  throwing  the  wrist  and 


UPPER   EXTREMITY — ARTERIES.  341 

hand  inwards,  the  latter  outwards.  Now  this  action  could  not 
be  effectively  produced  without  the  exertion  of  muscular  force 
upon  the  axis  of  support  to  the  wrist ;  and  we  therefore  find  that 
the  radius  alone  articulates  with  the  wrist,  and  administers  to  all 
its  movements,  while  the  ulna  is  reserved  as  the  especial  agent  in 
the  motions  of  the  elbow.  Besides  pronation  and  supination, 
the  wrist  possesses  powerful  flexion  and  extension,  and  to  this 
office  are  assigned  the  next  musctes,  jlexores  and  extensores  carpi. 
The  fingers  are  simply  supplied  for  all  their  numerous  movements 
of  flexion  and  extension,  by  three  flexors  situated  in  the  forearm, 
and  six  extensors  ;  one  flexor  and  three  extensors  being  intended 
for  the  especial  use  of  the  thumb.  The  remaining  muscle,  the 
palmaris  longus,  is  an  extensor  of  the  palmar  fascia,  which  pro- 
vides by  its  strength  and  elasticity  for  a  powerful  resistance  to 
shocks  received  upon  the  surface  of  the  hand.  The  muscles  of 
the  hand  are  flexors,  abductors,  and  adductors.  The  short  flexors 
of  the  thumb  and  little  finger  are  necessary  to  the  strength  of  grip 
so  characteristic  of  the  human  hand.  All  the  remaining  muscles 
are  abductors  and  adductors,  with  the  exception  of  the  palmaris 
brevis,  which  contracts  the  integument  on  the  side  of  the  hand, 
and  the  lurnbricales,  which  are  accessory  in  their  actions  to  the 
deep  flexor.  The  abductor  and  adductor  of  the  thumb  are 
known  by  those  names;  the  analogous  muscles  of  the  index 
finger  are  the  first  dorsal  and  first  palmar  interosseous ;  of  the 
middle  finger  the  two  next  dorsal  interossei  ;  of  the  ring  finger 
the  fourth  dorsal  and  second  palmar ;  and  of  the  little  finger  the 
abductor  minimi  digiti  and  third  palmar  interosseous.  These 
movements  of  abduction  and  adduction  are  highly  valuable  in 
the  grasp  of  large  or  irregular  bodies,  or  in  the  contraction  of  the 
bulk  of  the  hand  in  various  important  surgical  manipulations. 

The  main  artery  for  the  supply  of  the  upper  extremity  com- 
mences within  the  thorax,  and,  arching  over  its  brim,  passes 
beneath  the  clavicle  ;  hence  it  is  named  subclavian.  On  quitting 
the  side  of  the  chest,  it  is  received  into  the  space  which  inter- 
venes between  the  scapula  and  ribs,  and  acquires  the  name  of 
that  space — axillary.  It  then  runs  along  the  arm  to  the  bend  of 
the  elbow,  under  the  name  of  brachial.  Now  it  is  an  established 
principle  in  the  distribution  of  arteries,  that  they  always  select 
the  most  protected  situations  for  their  course.  Thus  they  are 
constantly  placed  on  the  inner  side  of  the  limb,  and  avoid  the 
convexities  of  joints,  where  they  would  be  subjected  to  injury, 
both  from  external  pressure  and  over  extension.  The  brachial 
artery  is  therefore  placed  along  the  inner  side  of  the  arm,  as  is 
the  femoral  in  the  thigh  ;  the  brachial  dips  deeply  into  the  space 
of  the  elbow,  as  does  the  popliteal  into  the  space  of  the  ham. 

Arrived  at  the  bend  of  the  elbow,  the  brachial  artery  accqmr 

29* 


342  THE   DISSECTOR. 

modates  itself  to  the  augmented  lateral  breadth  of  the  forearm, 
and  its  increased  number  of  components,  the  radius,  the  ulna, 
and  intermediate  space,  by  dividing  into  three  branches  corre- 
sponding with  these  three  parts,  the  two  bones  and  the  interos- 
seous  space.  Its  branches,  therefore,  are  radial,  ulnar,  and  inter- 
osseous  ;  as  in  the  leg  we  find  the  posterior  tibial  and  fibular 
corresponding  with  the  two  bones,  and  the  anterior  tibial  with 
the  interosseous  space. 

The  radial  artery  supplies  all  the  parts  placed  upon  the  radial 
side  of  the  forearm,  and  passing  between  the  two  heads  of  the 
first  dorsal  interosseous  muscle,  is  distributed  to  the  thumb  and 
deep  structures  in  the  hand,  under  the  name  of  the  deep  palmar 
arch.  The  ulnar  supplies  all  the  parts  placed  upon  the  ulnar 
side  of  the  forearm,  and  in  the  hand  forms  the  superficial  palmar 
arch,  from  which  the  branches  pass  off,  which  are  distributed  to 
the  fingers. 

In  the  supply  of  branches,  the  muscles  necessarily  come  in  for 
a  large  share,  which  receive  no  names  unless  they  assume  a  re- 
markable magnitude,  as  the  profunda  arteries.  Other  named 
branches  owe  their  names  to  peculiarity  of  structure,  and  are, 
therefore,  easily  remembered.  But  the  joints  which  are  exposed 
to  pressure  and  are  uncovered,  except  by  integument,  derive  an 
abundant  supply  of  branches  from  all  the  surrounding  sources. 
For  instance,  the  elbow  joint  is  provided  with  eight  nutrient 
branches,  the  superior  profunda  and  its  posterior  articular  branch, 
inferior  profunda,  anastomotica  magna,  radial  recurrent,  anterior 
and  posterior  ulnar  recurrents,  and  interosseous  recurrent.  The 
knee  has  seven  named  branches,  the  wrist  three,  and  the  ankle 
four. 

Thus  it  may  be  shown  that  the  principle  of  arrangement  of  the 
arteries,  as  of  the  muscles  and  the  rest  of  the  systems,  is  the  same 
throughout  the  entire  body :  the  exceptions  are  individualities 
that  associate  objects  of  importance  and  interest  with  their  ex- 
istence. 

The  veins  of  the  upper  extremity  are  the  superficial  and  the 
deep  :  the  former  are  placed  between  the  two  layers  of  the  super- 
ficial fascia,  the  latter  are  associated  with  the  arteries.  All  the 
arteries  of  the  limbs  and  trunk  which  are  below  the  second  mag- 
nitude are  accompanied  by  two  veins,  named  "  Venae  comites ;" 
thus  the  radial,  ulnar,  interosseous,  and  brachial  arteries,  with 
their  branches,  have  each  their  corresponding  venae  comites.  The 
axillary  and  subclavian  have  each  a  single  vein. 

The  lymphatic  vessels  are  rarely  seen  in  an  ordinary  dissection, 
excepting  under  very  favorable  circumstances,  as  in  anasarca, 
when  they  are  sometimes  observed,  as  white  opaque  threads, 
traversipg  t^e  transparent  jelly-like  cellular  substance,  and  enter- 


UPPER  EXTREMITY — NERVES.  343 

ing  the  lymphatic  glands  at  all  points  of  their  circumference. 
They  follow  in  their  course  the  direction  of  the  veins  to  which 
they  bear  an  analogy.  The  lymphatic  glands  are  accumulated  in 
the  loose  cellular  tissue  of  the  axilla,  arid  two  or  three  may  be 
met  with  in  the  course  of  the  basilic  vein. 

The  nerves  of  the  upper  extremity  are  derived  from  the  brachial 
plexus  which  is  formed  by  the  last  four  cervical  and  first  dorsal 
nerve.  A  plexus  is  the  means  by  which  nervous  branches 
destined  to  a  single  apparatus  are  associated  in  their  structure 
previously  to  distribution,  so  that  the  sensations  of  each  filament 
may  harmonize  with  all  the  rest,  and  produce  the  unity  of  im- 
pulse which  is  necessary  to  perfect  action.  For  it  is  evident  that 
if  an  impression  were  received  by  the  terminal  filament  of  any 
one  nerve,  and  excited  a  reflex  movement,  without  a  simultaneous 
impression  upon  the  other  nerves  of  the  same  limb  and  conse- 
quent muscular  movement,  that  an  opposition  of  action  would 
result;  which  is  inconsistent  with  natural  and  healthy  function. 
We  are,  therefore,  interested  in  the  complex  interlacements  and 
union  of  a  number  of  nerves  in  the  formation  of  a  plexus,  when 
we  reflect  upon  the  important  benefits  which  such  a  disposition 
confers. 

The  branches  which  are  given  off  by  the  brachial  or  axillary 
plexus  are,  1st,  those  distributed  to  the  shoulder  and  neighboring 
part  of  the  chest ;  and  2d,  those  destined  to  the  arm.  The  former 
are  named  thoracic  and  scapular :  the  latter  consist  of  six  nerves  ; 
— one,  which,  supplies  the  muscles  about  the  shoulder  joint,  the 
circumflex;  two,  going  to  the  integument  of  the  arm,  external  and 
internal  cutaneous  ;  and  three,  like  the  three  arteries,  supplying 
the  forearm  and  hand,  musculo-spiral,  ulnar,  and  median. 

Let  us  now  proceed  to  the  dissection  of  the  upper  extremity, 
beginning  with  the — 

ANTERIOR  THORACIC  REGION. 

Dissection. — Make  an  incision  along  the  line  of  the  clavicle,  from  its 
sternal  extremity,  for  about  two-thirds  of  its  length  ;  carry  a  second  in- 
cision longitudinally  along  the  middle  of  the  sternum  to  its  lower 
extremity,  and  a  third  along  the  lower  border  of  the  pectoral  is  major 
muscle  and  anterior  border  of  the  axilla  to  the  arm.  Dissect  back  the 
integument  from  the  area  included  within  these  incisions.  Then,  in 
order  further  to  expose  the  side  of  the  chest  and  the  axilla,  carry  a  fourth 
incision  from  the  angle  of  the  preceding  at  the  lower  end  of  the  sternum 
horizontally  outwards  to  the  side  of  the  chest,  three  or  four  inches'  below 
the  axilla,  and  reflect  the  integument  as  before.  The  dissector  should 
next  proceed  to  seek  for  the  cutaneous  nerves  situated  in  the  superficial 
fascia,  and  in  the  upper  part  of  the  region  he  will  find  a  thin  stratum  of 
muscular  fibres,  a  part  of  the  cutaneous  muscle  of  the  side  of  the  neck, 
platysma  myoides.  He  may  then  study  the  mammary  gland,  and,  after 
this  has  been  completed,  dissect  off  the  deep  fascia  from  the  whole  of 


344  THE  DISSECTOR. 

the  region  and  examine  the  muscles.  In  removing  the  deep  fascia, 
the  student  must  be  reminded  of  the  necessity  of  dissecting  in  the  course 
of  the  fibres  of  the  muscles,  and  his  progress  will  be  facilitated  by  put- 
ting the  muscles  on  the  stretch. 

The  cutaneous  nerves  of  the  anterior  thoracic  region  are,  seve- 
ral cutaneous  branches  from  the  cervical  plexus,  which  pass  down 
over  the  clavicle  and  are  distributed  to  the  integument  covering 
the  pectoralis  major  muscle ;  anterior-cutaneous  of  the  thorax, 
which  pierce  the  pectoralis  major  muscle  near  the  sternum,  and 
are  reflected  outwards  to  the  integument  and  mammary  gland ; 
and  lateral  cutaneous  nerves  of  the  thorax,  which  issue  from  the 
intercostal  spaces  on  the  side  of  the  chest,  and  proceed  upwards 
and  forwards  around  the  lower  border  of  the  pectoralis  major  to 
the  integument  covering  that  muscle,  and  to  the  mammary  gland. 
On  the  side  of  the  chest  in  and  below  the  axilla  are  several  cuta- 
neous nerves,  proceeding  from  the  lateral  cutaneous  branches  of 
the  intercostal  nerves :  these  are  the  posterior  branches  of  the 
lateral  cutaneous  nerves.  Some  pass  backwards  over  the  poste- 
rior border  of  the  axilla,  and  are  distributed  to  the  integument 
covering  the  latissimus  dorsi  muscle  and  lower  part  of  the 
scapula ;  and  two,  proceeding  from  the  second  and  third  inter- 
costal nerves,  are  distributed  to  the  integument  of  the  inner  side 
of  the  arm  under  the  name  of  inter costo-humeral  nerves. 

Mammary  Gland. — The  mamma  may  be  best  studied  in  the 
female,  although  it  exists  also  in  the  male.  It  is  situated  in  the 
pectoral  region,  being  separated  from  the  pectoralis  major  mus- 
cle by  the  deep  fascia  ;  and  occupies  a  circular  space  which 
extends  longitudinally  from  the  third  to  the  sixth  rib,  and  hori- 
zontally from  near  the  sternum  to  the  axilla.  Its  base  is  some- 
what elliptical,  the  long  diameter  corresponding  with  the  direc- 
tion of  the  fibres  of  the  pectoralis  major  muscle ;  and  the  left 
mamma  is  generally  a  little  larger  than  the  right. 

Near  the  centre  of  the  convexity  of  each  mamma  is  a  small 
prominence  of  the  integument,  called  the  nipple  (mammilla),  which 
is  surrounded  by  an  areola  having  a  colored  tint.  In  females 
of  fair  complexions,  before  impregnation,  the  color  of  the  areola 
is  a  delicate  pink ;  after  impregnation,  it  assumes  a  brownish 
hue,  which  deepens  in  color  as  pregnancy  advances  ;  and  after 
the  birth  of  a  child,  the  brownish  tint  continues  through  life. 

The  areola  is  furnished  with  a  considerable  number  of  seba- 
ceous glands,  which  secrete  a  peculiar  fatty  substance  for  the  pro- 
tection of  the  delicate  integument  around  the  nipple.  During 
suckling  these  glands  are  increased  in  size,  and  have  the  appear- 
ance of  small  pimples,  projecting  from  the  skin.  At  this  period, 
they  serve  by  their  increased  secretion  to  defend  the  nipple  and 
areola  from  the  excoriating  action  of  the  mouth  of  the  infant. 


MAMMARY  GLAND. 


345 


In  structure,  the  mamma  is  a  conglomerate  gland,  and  consists 
of  lobes,  which  are  held  together  by  a  dense  and  firm  cellular 
tissue  ;  the  lobes  are  composed  of  lobules,  and  the  lobules  of 
minute  csecal  vesicles,  the  ultimate  terminations  of  the  excretory 
ducts. 

The  excretory  ducts  (tubuli  lactiferi,  galactophori),  from  fifteen 

SUPERFICIAL  NERVES  Fig.  105. 

AND  MUSCLES  OP  THE 
TRUNK. — a.  The  platys- 
ma  myoides  muscle,  b, 

b.  The  sterno-mastoid. 

c,  c.  The  trapezius.     d. 
Part  of  the  deltoid,    e. 
The  pectoralis  major.  /. 
The  biceps,     g.  The  co- 
raco-brachialis.    h.  The 
triceps.  *.  The  teres  ma- 
jor,   k.  The  teres  minor. 
/,  /.  Thelatissimusdorsi. 
771,  m.  The  serratusmag- 
nus.  The  upper  m  is  situ- 
ated in  the  lower  part  of 
the  cavity  of  the  axilla. 
n.  The  external  oblique 
muscle  ;     the     letter    is 
]>l;ir»'<l  on  the  linea  semi- 
lunaris.    g.  The  gluteus 
maximus.     r.  Supracla- 
vicular  branches  of  the 
cervical  plexus  :  the  an- 
terior branch  is  the  ster- 
nal ;    the   posterior  the 
acromial.  s,s.  Anterior 
cutaneous  nerves,     t,  t. 
Anterior  branches  of  the 
lateral  cutaneous  nerves. 
v,  v.  Posterior  branches 
of  the  lateral  cutaneous 
nerves,     w.   The  inter- 
costo-humeral      nerve  ; 
which        communicates 
with  x,  a  branch  of  the 
nerve  of  Wrisberg.     y. 
The  branch  of  the  lateral 
cutaneous  branch  of  the 
third   intercostal   nerve 
to  the  arm.     z,  z.  Pos- 
terior cutaneous  nerves. 

1,  1.  Cutaneous  branches  derived  from  the  lumbar  nerves.  2.  The  iliac  branch 
of  the  ilio-hypogastric  nerve.  3.  Its  hypogastric  branch.  4.  The  lateral  cuta- 
neous branch  of  the  last  dorsal  nerve.  2,  and  4,  are  placed  on  the  crest  of  the 
ilium.  5.  The  external  cutaneous  nerve  of  the  thigh,  giving  off  cutaneous 
branches  to  the  hip. 

to  twenty-five  in  number,  commence  by  small  openings  at  the 
apex  of  the  nipple,  and  pass  inwards,  parallel  with  each  other, 
towards  the  central  part  of  the  gland,  where  they  form  dilatations 


346  THE   DISSECTOR. 

(ampullae),  and  give  off  numerous  branches  to  ramify  through 
the  gland  to  their  ultimate  terminations  in  the  minute  lobules. 

The  ducts  and  caeca!  vesicles  are  lined,  throughout,  by  a  mu- 
cous membrane,  which  is  continuous  at  the  apex  of  the  nipple 
with  the  integument. 

In  the  nipple  the  excretory  ducts  are  surrounded  by  a  tissue 
analogous  to  the  dartos  of  the  scrotum,  to  which  the  power  of 
erectility  of  the  nipple  seems  due.  There  is  no  appearance  of 
any  structure  resembling  erectile  tissue. 

The  mammae  are  supplied  with  arteries  from  the  thoracic 
branches  of  the  axillary,  from  the  intercostals,  and  from  the  in- 
ternal mammary.  The  veins  form  an  incomplete  circle  around 
the  base  of  the  nipple  (circulus  venosus  Halleri),  from  which 
larger  veins  conduct  the  blood  to  the  circumference  of  the  gland, 
and  by  their  communications  form  a  plexus  on  its  surface.  They 
terminate  in  the  axillary  vein,  the  internal  mammary,  the  inter- 
costals, and  the  jugular  veins. 

The  lymphatics  take  the  course  of  the  veins,  inwards,  to  the 
anterior  mediastinal  glands ;  and  outwards  along  the  border  of 
the  pectoralis  major  to  the  axillary  glands. 

The  nerves  of  the  mammary  gland  are  derived  from  the  ante- 
rior cutaneous  branches  of  the  third,  fourth,  and  fifth  intercostal 
nerves;  and  from  the  lateral  cutaneous  branches  of  the  same 
nerves. 

The  MUSCLES  of  the  anterior  thoracic  region  are  the — 
Pectoralis  major. 
Pectoralis  minor. 
Subclavius. 

The  PECTORALTS  MAJOR  muscle  arises  from  the  sternal  half  of 
the  clavicle,  half  the  sternum  its  whole  length,  the  cartilages  of 
all  the  true  ribs,  excepting  the  first  and  last,  and  the  aponeurosis 
of  the  external  oblique  muscle  of  the  abdomen.  It  is  inserted  by 
a  broad  tendon  into  the  anterior  bicipital  ridge  of  the  humerus. 

That  portion  of  the  muscle  which  arises  from  the  clavicle  is 
separated  from  that  connected  with  the  sternum  by  a  distinct 
cellular  interspace  ;  hence  we  speak  of  the  clavicular  portion  and 
sternal  portion  of  the  pectoralis  major.  The  fibres  from  this  very 
extensive  origin  converge  towards  a  narrow  insertion,  giving  the 
muscle  a  radiated  appearance.  But  there  is  a  peculiarity  about 
the  formation  of  its  tendon  which  must  be  carefully  noted.  The 
whole  of  the  lower  border  is  folded  inwards  upon  the  upper  por- 
tion, so  that  the  tendon  is  doubled  upon  itself.  Another  pecu- 
liarity results  from  this  arrangement:  the  fibres  of  the  upper  por- 
tion of  the  muscle  are  inserted  into  the  lower  part  of  the  ridge, 
and  those  of  the  lower  portion  into  the  upper  part. 


PECTORALIS   MAJOR.  347 

The  pectoral  is  major  muscle  is  separated  from  the  deltoid  by 
a  deep  cellular  interspace,  in  which  are  seen  the  cephalic  vein 
and  the  descending  branch  of  the  thoracica  acromialis  artery. 
(Fig.  106,  11.) 

Operations. — The  pectoralis  major  forms  the  ground  plan  of  three  ope- 
rations required  for  the  ligature  of  the  axillary  artery  in  the  upper  part 
of  its  course. 

Thejirst  and  more  usual  operation  is  to  make  an  incision  parallel  with 
and  about  three  quarters  of  an  inch  below  the  clavicle.  The  incision 
should  be  three  inches  in  length,  and  extend  a  little  beyond  the  inter- 
space of  the  deltoid  and  pectoralis  muscle.  It  should  divide  the  integu- 
ment, superficial  fascia,  platysma  myoides,  and  clavicular  portion  of  the 
pectoralis  major.  The  posterior  layer  of  the  sheath  of  the  pectoralis  must 
be  divided  on  a  director,  and  the  sheath  of  the  axillary  vessels  opened 
with  care.  The  axillary  vein  of  large  size  lies  in  front,  and  conceals  the 
artery  :  behind  the  artery  are  the  nerves  of  the  brachial  plexus.  In  this 
operation  the  cephalic  vein  is  endangered,  and  several  branches  of  the 
superior  thoracic  artery  and  thoracica  acromialis  cut  across. 

Another  operation,  rarely  practised,  is  that  of  Desault.  It  consists  in 
making  an  incision  two  inches  and  a  half  long  in  the  line  of  the  inter- 
space between  the  pectoralis  major  and  deltoid.  The  cephalic  vein  is 
drawn  aside  and  the  muscles  separated  so  as  to  expose  the  tendon  of  the 
pectoralis  minor,  which  is  to  be  cut  across,  and  the  vessels  brought  into 
view  by  raising  them  on  the  finger.  The  descending  branch,  and  one  or 
two  of  the  thoracic  branches  of  the  thoracica  acromialis  artery,  are  neces- 
sarily divided. 

The  third  operation  (Lisfranc's)  is  equally  objectionable.  The  incision, 
three  inches  in  length,  is  made  in  the  direction  of  the  line  of  separation 
of  the  sternal  and  clavicular  portions  of  the  pectoralis  major,  and  the  two 
portions  of  the  muscle  separated  in  order  to  reach  the  artery. 

Dissection. — The  pectoralis  major  is  now  to  be  removed  by  dividing  its 
fibres  along  the  lower  border  of  the  clavicle,  and  then  carrying  the  inci- 
sion perpendicularly  downwards,  parallel  to  the  sternum,  and  at  about 
three  inches  from  its  border.  Divide  some  loose  cellular  tissue,  and 
several  small  branches  of  the  thoracic  arteries,  and  reflect  the  muscle 
outwards.  We  thus  bring  into  view  a  region  of  considerable  interest, 
from  which  the  fat  and  cellular  tissue  must  be  carefully  removed. 

In  the  middle  of  this  region  is  the  pectoralis  minor  muscle 
(Fig.  106, 4),  and  above  it  a  triangular  space  bounded  superiorly 
by  the  costo-coracoid  membrane,  3,  which  covers  in  the  subcla- 
vius  muscle,  and  by  the  second  rib  and  two  adjoining  interspaces 
internally.  In  this  triangular  space,  5,  are  found  the  subclavian 
vein,  6,  the  subclavian  artery,  7,  and  the  brachial  plexus  of  nerves, 
8,  all  resting  on  the  first  rib;  the  acromial  thoracic,  10,  and  supe- 
rior thoracic  artery,  9,  with  their  veins  and  nerves,  and  the  cepha- 
lic vein,  11.  Below  the  pectoralis  minor,  the  axillary  artery  is 
seen  embraced  by  the  two  heads  of  the  median  nerve,  16,  having 
to  its  inner  side  the  axillary  vein,  and  in  front  the  inferior  tho- 
racic, 13,  and  axillary  thoracic,  14,  branches. 

The  PECTORALIS  MINOR  arises  by  three  digitations  from  the 


348 


THE   DISSECTOR. 


third,  fourth,  and  fifth  ribs,  and  is  inserted  into  the  anterior  border 
of  the  coracoid  process  of  the  scapula  by  a  broad  tendon. 


Fig.  106. 


THE  VESSELS  AND  NERVES 
OF  THE  DEEP  PECTORAL  RE- 
GION.— 1.  The  deltoid  muscle. 
2.  The  clavicle.  3.  The  sub- 
clavius  muscle,  covered  in  by 
the  costo-coracoid  membrane. 

4.  The  pectoralis  minor  muscle. 

5.  The  triangular  space,  in  which 
the  subclavian  artery  is  tied  be- 
low the  clavicle  ;  and  which  con- 
tains,   6.   The  subclavian  vein. 
7.    The   subclavian    artery.      8. 
The  brachial  plexus  of  nerves. 
9.  The  superior  thoracic  artery 
and   nerve.     10.    The   thoracic 
branch    of  the    thoracica  acro- 
mialis,    artery.       11.     The    de- 
scending branch   of  the  thora- 
cica acromialis,  descending  by 
the    side  of  the  cephalic  vein. 
12.  The  acromial  branch  of  the 
thoracica  acromialis.     13.    The 
inferior     thoracic     artery     and 
nerve.     14.  The  thoracica  alaris 
branch  of  the    axillary  artery. 
15.  The  internal  cutaneous  and 
ulnar  nerves  resting  on  the  axil- 
lary vein.   16.  The  median  nerve 
embracing  the   axillary  artery, 

with  its  two  heads.      17.  The  external  cutaneous  nerve,   piercing  the  coraco- 
brachialis  muscle.      18.    The  coraco-brachialis.     19    The  biceps  muscle. 

The  SUBCLAVIUS  muscle  arises  by  a  round  tendon  from  the  car- 
tilage of  the  first  rib,  and  is  inserted  into  the  under  surface  of  the 
clavicle  for  nearly  half  its  length.  This  muscle  is  concealed  by 
the  costo-coracoid  membrane,  an  extension  of  the  deep  cervical 
fascia,  by  which  it  is  invested. 

The  upper  part  of  the  axillary  space  above  the  pectoralis  minor,  and 
the  larger  portion  of  the  space  below  it,  should  now  be  carefully  cleared 
of  cellular  tissue  and  fat,  and  the  vessels  and  nerves  made  out  which 
occupy  the  axillary  space  and  give  branches  to  the  surrounding  parts. 
In  the  loose  cellular  tissue  of  the  axilla,  at  its  lower  part  and  lying  nearer 
to  the  thorax  than  the  arm,  is  a  cluster  of  ten  or  twelve  lymphatic  glands, 
which  receive  the  lymphatic  vessels  from  the  front  and  back  of  the  chest 
and  mammary  gland.  The  efferent  vessels  from  these  glands  pass  up- 
wards by  the  side  of  the  subclavian  vessels  to  the  root  of  the  neck,  and 
terminate  in  the  great  lymphatic  ducts.  To  facilitate  the  dissection  of 
the  axilla,  the  pectoralis  minor  muscle  may  be  drawn  aside,  or  even 
divided  across. 

The  AXILLA  or  armpit  is  the  space  between  the  side  of  the 
chest  and  the  arm.  In  form  it  resembles  a  triangular  cone,  the 


AXILLARY   ARTEEY.  349 

apex  being  above  at  the  clavicle,  the  base  below  at  the  lower 
borders  of  the  pectoralis  major  and  latissimus  dorsi.  It  is  broad 
from  before  backwards  near  the  thorax,  but  narrows  towards  the 
humerus ;  and  is  bounded  in  front  by  the  pectoralis  major  and 
minor  muscles ;  behind  by  the  subscapularis,  teres  major,  and 
latissimus  dorsi;  internally  by  the  four  upper  ribs  with  their 
intercostal  muscles  and  part  of  the  serratus  magnus  muscle  ;  and 
externally  by  the  biceps,  coraco-brachialis,  and  humerus. 

The  parts  contained  within  the  axilla  are  the  axillary  artery 
and  vein,  with  their  branches;  the  brachial  plexus  of  nerves,  with 
its  branches ;  the  two  intercosto-humeral  nerves  ;  the  external 
respiratory  nerve  of  Bell,  which  lies  upon  the  serratus  magnus 
muscle  ;  and  from  ten  to  twelve  lymphatic  glands. 

The  axillary  vessels  at  their  point  of  emergence  from  beneath 
the  subclavius  muscle,  are  invested  for  a  short  distance  by  a  thin 
sheath  derived  from  the  costo-coracoid  membrane.  The  tho- 
racica  acromialis  artery  and  anterior  thoracic  nerve  are  seen  to 
perforate  this  sheath  in  their  course  forward;  the  sheath  must  be 
removed  in  order  to  bring  the  axillary  vessels  completely  into 
view. 

The  AXILLARY  ARTERY  passes  outwards  and  downwards  with 
a  gentle  curve,  through  the  axillary  space  from  the  lower  border 
of  the  first  rib,  to  the  lower  border  of  the  tendons  of  the  latissi- 
mus dorsi  and  teres  major,  where  it  becomes  the  brachial. 

Relations. — In  its  course  it  is  in  relation  in  front  with  the  pec- 
toralis major,  pectoralis  minor,  and  again  with  the  pectoralis  major, 
being  immediately  invested  with  the  aponeurotic  sheath  derived 
from  the  costo-coracoid  membrane ;  internally,  it  has  the  first 
intercostal  muscle,  the  first  serration  of  the  serratus  magnus,  the 
axillary  vein,  and  at  its  lower  part  the  brachial  plexus;  externally 
and  posteriorly  it  is  approached  by  the  brachial  plexus,  a  cellular 
interval  existing  between  them  above ;  then  it  is  in  relation  with 
the  subscapularis,  the  coraco-brachialis,  the  teres  major  and  latis- 
simus dorsi.  The  brachial  plexus  of  nerves  lies  to  the  outer  side 
of  the  artery  above,  being  separated  from  it  by  a  cellular  inter- 
space, but  approaches  it  in  the  middle  of  its  course,  and  then 
completely  surrounds  the  artery ;  the  median  and  external  cuta- 
neous nerve  lying  to  its  outer  side ;  the  ulnar,  the  internal  cutaneous 
and  internal  cutaneous  of  Wrisberg  to  its  inner  side,  and  the 
musculo-spiral  and  circumflex  behind. 

A  slight  inspection  of  this  artery  and  its  numerous  relations, 
will  serve  to  show  that  its  ligature  would  be  an  extremely  inju- 
dicious and  dangerous  operation,  warranted  only  by  the  pressure 
of  extreme  circumstances.  But  the  student  may  be  called  upon 
to  give  the  steps  of  the  operation  :  he  must,  therefore,  reflect  upon 
30 


350  THE   DISSECTOR. 

the  position,  depth,  and  relations  of  the  artery.  A  superficial 
vessel  requires  only  a  short  incision,  the  length  increasing  with 
the  depth  of  the  artery. 

Operations. — The  operations  on  the  axillary  artery  in  the  upper  part 
of  its  course  have  been  already  examined  (page  347)  ;  we  have  now  to 
consider  the  mode  of  tying  it  in  its  lower  part.  An  incision,  two  inches 
in  length,  is  to  be  made  along  the  hollow  of  the  axilla,  at  one  third  from 
its  anterior  border.  This  incision  should  divide  the  integument  and 
superficial  fascia  ;  in  the  next  place  the  deep  fascia  should  be  cut  through 
along  the  border  of  the  coraco-brachialis  muscle,  when  the  median  nerve 
will  be  brought  into  view  :  behind  the  median  nerve  is  situated  the  axil- 
lary artery.  When  the  deep  fascia  is  divided,  the  axillary  vein  must 
be  drawn  inwards  and  the  forearm  bent  to  relax  the  nerves  ;  the  operator 
then  pushes  aside  the  median  nerve  and  carries  the  needle  around  the 
artery.  The  objections  to  this  operation  are  numerous.  The  breaking 
up  of  the  loose  cellular  tissue  may  give  rise  to  suppuration  and  sinuses. 
Nerves  may  be  injured  or  tied,  the  vein  or  veins  may  be  wounded,  and, 
even  when  the  artery  is  reached,  it  is  tied  in  the  midst  of  a  number  of 
branches. 

Branches. — The  branches  of  the  axillary  artery  are  seven  in 
number : — 

Superior  thoracic,  Subscapular, 

Thoracica  acromialis,  Circumflex  anterior, 

Long  thoracic,  Circumflex  posterior. 

Thoracica  alaris, 

The  superior  thoracic  and  thoracica  acromialis  are  found  in 
the  triangular  space  above  the  pectoralis  minor  ;  the  long  thoracic 
and  thoracica  alaris,  below  the  pectoralis  minor ;  and  the  three 
remaining  branches  below  the  lower  border  of  the  subscapularis. 

The  superior  thoracic,  the  highest  of  the  branches  of  the  axil- 
lary, and  sometimes  derived  from  the  next,  passes  inwards  to  the 
chest  in  front  of  the  pectoralis  minor  muscle,  and  is  distributed 
to  the  pectoral  muscles  and  walls  of  the  chest.  It  anastomoses 
with  the  intercostal  and  mammary  arteries. 

The  thoracica  acromialis  is  a  short  trunk  which  proceeds  from 
the  axillary  in  the  space  above  the  pectoralis  minor  muscle,  and 
divides  into  three  sets  of  branches — thoracic,  which  are  distributed 
to  the  pectoral  muscles,  serratus  magnus,  and  mammary  gland ; 
acromial,  which  pass  outwards  to  the  acromion,  and  inosculate 
with  branches  of  the  supra-scapular  artery  ;  and  descending  a 
single  branch,  which  follows  the  interspace  between  the  deltoid 
and  pectoralis  major  muscles,  and  is  in  relation  with  the  cephalic 
vein. 

The  long  thoracic  (external  mammary)  follows  the  lower  border 
of  the  pectoralis  minor  to  the  side  of  the  chest.  It  is  distributed 
to  the  pectoralis  major  and  minor,  serratus  magnus,  and  mammary 
gland ;  inosculating  with  the  superior  thoracic,  intercostal,  and 
mammary  arteries. 


AXILLARY  ARTERY — BRANCHES. 


351 


The  thoracica  alaris  is  a  small  branch  distributed  to  the  plexus 
nerves  and  glands  in  the  axilla.     It  is  frequently  wanting,  its 


THE  AXILLARY  AND  BRACHIAL  ARTE- 
RY, WITH  THEIR  BRANCHES. — 1.  The 
deltoid  muscle.  2.  The  biceps.  3.  The 
tendinous  process  given  off  from  the  ten- 
don of  the  biceps,  to  the  deep  fascia  of 
the  forearm.  It  is  this  process  which 
separates  the  median  basilic  vein  from  the 
brachial  artery.  4.  The  outer  border  of 
the  brnchialis  anticus  muscle.  5.  The 
supinator  longus.  6.  The  coraco-brachi- 
alis.  7.  The  middle  portion  of  the  triceps 
muscle.  8.  Its  inner  head.  9.  The  ax- 
illary artery.  10.  The  brachial  artery ; — 
a  dark  line  marks  the  limit  between  these 
two  vessels.  11.  The  thoracica  acromialis 
artery  dividing  into  its  three  branches  ; 
the  number  rests  upon  the  coracoid  pro- 
cess. 12.  The  superior  and  long  thoracic 
arteries.  13.  The  serratus  magnus  muscle. 
14.  The  sub-scapular  artery.  The  pos- 
terior circumflex  and  thoracica  axillaris 
branches  are  seen  in  the  figure  between 
the  inferior  thoracic  and  sub-scapular. 
The  anterior  circumflex  is  observed,  be- 
tween the  two  heads  of  the  biceps,  crossing 
the  neck  of  the  humerus.  15.  The  supe- 
rior profunda  artery.  16.  The  inferior 
profunda.  17.  The  anastomotica  inoscu- 
lating inferiorly  with  the  anterior  ulnar 
recurrent.  18.  The  termination  of  the 
superior  profunda,  inosculating  with  the 
radial  recurrent  in  the  interspace  between 
the  brachialis  anticus  and  supinator  lon- 
gus. 


Fig.  107, 


place  being  supplied  by  a  branch  from  one  of  the  other  thoracic 
arteries. 

The  subscapular  artery,  the  largest  of  the  branches  of  the  axil- 
lary, runs  along  the  lower  border  of  the  subscapularis  muscle,  to 
the  inferior  angle  of  the  scapula,  where  it"  inosculates  with  the 
posterior  scapular,  a  branch  of  the  subclavian.  It  supplies  the 
muscles  on  the  under  surface  and  inferior  border  of  the  scapula, 
and  side  of  the  chest.  At  about  an  inch  and  a  half  from  the 
axillary,  it  gives  off  a  large  branch,  the  dorsalis  scapulas,  which 
passes  backwards  through  the  triangular  space  bounded  by  the 
teres  minor,  teres  major,  and  scapular  head  of  the  triceps,  and 
beneath  the  infra-spinatus  to  the  dorsum  of  the  scapula,  where  it 
is  distributed,  inosculating  with  the  supra-scapular  and  posterior 
scapular  arteries. 

The  circumflex  arteries  wind  around  the  neck  of  the  humerus. 


352  THE   DISSECTOR. 

The  anterior,  very  small,  passes  beneath  the  coraco-brachialis  and 
short  head  of  the  biceps,  and  sends  a  branch  upwards  along  the 
bicipital  groove  to  supply  the  shoulder-joint. 

The  posterior  circumflex,  of  larger  size,  passes  backwards 
through  the  quadrangular  space  bounded  by  the  teres  minor  and 
major,  the  scapular  head  of  the  triceps  and  the  humerus,  and  is 
distributed  to  the  deltoid  muscle  and  shoulder  joint :  sometimes 
this  artery  is  a  branch  of  the  superior  profunda  of  the  brachial. 
It  then  ascends  behind  the  tendon  of  the  teres  major,  and  is  dis- 
tributed to  the  deltoid  without  passing  through  the  quadrangular 
space.  The  posterior  circumflex  artery  sends  branches  to  the 
shoulder-joint. 

The  AXILLARY  VEIN  lies  to  the  inner  side  of  the  artery  through- 
out its  course,  and  from  its  large  size  partly  conceals  it  from 
view.  It  is  the  continuation  of  the  basilic  vein.  At  its  com- 
mencement it  receives  the  large  trunk  resulting  from  the  junction 
of  the  brachial  veins,  and  in  its  course,  the  veins  returning  the 
blood  from  the  branches  of  the  axillary  artery ;  in  the  space  above 
the  pectoralis  minor  it  receives  the  cephalic  vein. 

The  dissection  of  the  nerves  of  the  axilla  will  be  facilitated  by  the 
division  of  the  axillary  artery,  by  turning  it  down,  and  removing  its 
smaller  branches  ;  the  smaller  branches  of  the  plexus  may  then  be  fol- 
lowed to  their  destination. 

The  BRACHIAL  PLEXUS  OP  NERVES  formed  in  the  root  of  the 
neck  by  the  last  four  cervical  and  first  dorsal  nerve,  enters  the 
axillary  space  as  two  cords,  from  which  a  third,  formed  by  a 
branch  from  each  of  the  others,  soon  proceeds.  The  three  cords 
partly  surround  the  artery,  one  lying  to  its  outer  side,  one  to  the 
inner  side,  and  one  behind.  A  branch  from  the  inner  cord  and 
one  from  the  outer  cord  then  unite  in  front  of  the  artery  to  form 
the  median  nerve,  and  complete  the  circle  around  it. 

The  branches  of  the  brachial  plexus  are — from  the  outer  cord, 
one  of  the  anterior  thoracic  nerves,  the  external  cutaneous  nerve, 
and  the  outer  head  of  the  median;  from  the  inner  cord,  the 
other  anterior  thoracic  nerve,  the  other  head  of  the  median,  the 
internal  cutaneous,  the  lesser  internal  cutaneous  of  Wrisberg,  and 
the  ulnar ;  and  from  the  posterior  cord,  the  subscapular  nerves, 
the  circumflex,  and  musculo-spiral. 

Besides  the  above  branches,  the  brachial  plexus,  while  in  the 
neck,  gives  off  several  superior  muscular  branches:  one  to  the 
subclavius  muscle,  one  to  the  rhomboid  muscles  and  levator  an- 
guli  scapulas;  one,  of  large  size,  the  suprascapular ;  and  a  long 
and  slender  nerve  which  passes  down  the  thoracic  wall  of  the 
axilla,  the  posterior  thoracic,  or  external  respiratory  nerve  of 
Bell. 

In  reference  to  their  distribution,  the  branches  of  the  brachial 


BRACHIAL  PLEXUS  OP  NERVES.          353 

plexus  may  be  arranged  in  three  groups — thoracic,  scapular,  and 
brachial,  as  follows  : — 

Thoracic.  Scapular. 

Anterior  thoracic,  Superior  muscular, 

Posterior  thoracic.  Suprascapular, 

Subscapular. 

Brachial. 

External  or  musculo-cutaneous, 

Internal  cutaneous, 

Lesser  internal  cutaneous, 

Median, 

TJlnar, 

Musculo-spiral, 

Circumflex. 

The  anterior  thoracic  nerves  proceed,  the  one  from  the  external 
cord  of  the  plexus,  the  other  from  the  internal  cord.  The  former, 
the  external  or  superficial  branch,  crosses  the  axillary  artery  in 
the  space  above  the  pectoralis  minor  to  the  front  of  the  chest, 
and  is  distributed  to  the  pectoralis  major  muscle.  The  internal 
or  deeper  branch  issues  from  between  the  axillary  artery  and 
vein,  and  after  forming  a  loop  of  communication  with  the  preced- 
ing, is  distributed  to  the  under  surface  of  the  pectoralis  minor 
and  major. 

The  posterior  thoracic,  or  external  respiratory  of  Bell,  is  formed 
by  the  junction  of  two  offsets,  one  from  the  fifth,  the  other  from 
the  sixth  cervical  nerve;  it  crosses  behind  the  brachial  plexus  to 
reach  the  side  of  the  chest,  and  descends  upon  the  serratus  mag- 
nus  to  the  lower  part  of  that  muscle,  to  which  it  is  distributed. 

The  suprascapular  nerve  arises  from  the  fifth  cervical  nerve, 
and  proceeds  obliquely  outwards  to  the  suprascapular  notch;  it 
then  passes  through  the  notch,  crosses  the  supra-spinous  fossa 
beneath  the  supra-spinatus  muscle,  and  running  in  front  of  the 
concave  margin  of  the  spine  of  the  scapula  enters  the  infra- 
spinous  fossa.  It  is  distributed  to  the  supra-spinatus  and  infra- 
spinatus  muscle,  and  sends  two  or  three  filaments  to  the  shoulder- 
joint. 

The  subscapular  nerves  are  three  in  number ;  one  supplies  the 
upper  part  of  the  subscapularis  muscle;  the  second  (long~ sub- 
scapular),  follows  the  course  of  the  subscapular  artery,  and  is 
distributed  to  the  latissimns  dorsi ;  the  third  is  distributed  to  the 
lower  part  of  the  subscapularis  muscle  and  teres  major. 

The  brachial  group  of  nerves  must  be  left  until  the  dissection  of  the 
arm  is  proceeded  with.  At  present,  and  until  the  time  arrives  for  the 
inspection  of  the  cavity  of  the  thorax,  the  student  may  examine  that  por- 

30* 


354  THE   DISSECTOR. 

tion  of  the  latissimus  dorsi  which  is  visible  from  the  front,  the  serratus 
magnus,  and  the  muscles  and  vessels  of  the  parietes  of  the  chest. 

The  LATISSIMUS  DORSI  muscle  covers  the  whole  of  the  lower 
part  of  the  back  and  loins.  It  arises  from  the  spinous  processes 
of  the  six  inferior  dorsal  vertebra,  from  all  the  lumbar  and 
sacral  spinous  processes,  from  the  posterior  third  of  the  crest 
of  the  ilium,  and  from  the  three  lower  ribs  :  the  latter  origin 
takes  place  by  muscular  slips  which  indigitate  with  the  external 
oblique  muscle  of  the  abdomen.  The  fibres  from  this  extensive 
origin  converge  as  they  ascend,  and  cross  the  inferior  angle  of 
the  scapula ;  they  then  curve  around  the  lower  border  of  the 
teres  major  muscle,  and  terminate  in  a  short  quadrilateral  tendon, 
which  lies  in  front  of  the  tendon  of  the  teres,  and  is  inserted  into 
the  bicipital  groove.  A  synovial  bursa  is  interposed  between 
the  muscle  and  the  lower  angle  of  the  scapula,  and  another  be- 
tween its  tendon  and  that  of  the  teres  major.  The  muscle  fre- 
quently receives  a  small  fasciculus  from  the  scapula  as  it  crosses 
its  inferior  angle. 

The  SERRATUS  MAGNUS  (serratus,  indented  like  the  edge  of  a 
saw)  arises  by  fleshy  serrations  from  the  nine  upper  ribs  except- 
ing the  first,  and  extends  backwards  upon  the  side  of  the  chest, 
to  be  inserted  into  the  whole  length  of  the  base  of  the  scapula 
upon  its  anterior  aspect.  In  structure,  the  muscle  is  composed 
of  three  portions,  a  superior  portion,  formed  by  two  serrations 
attached  to  the  second  rib,  and  inverted  into  the  inner  surface 
of  the  superior  angle  of  the  scapula, — a  middle  portion,  com- 
posed of  the  serrations  connected  with  the  third  and  fourth  ribs, 
and  inserted  into  the  greater  part  of  the  posterior  border, — and 
an  inferior  portion,  consisting  of  the  last  five  serrations  which  in- 
digitate  with  the  obliquus  externus ;  they  forma  thick  muscular  fas- 
ciculus, which  is  inserted  into  the  scapula  near  its  inferior  angle. 

The  intercostal  muscles  are  two  planes  of  muscular  and  tendi- 
nous fibres  directed  obliquely  between  the  adjacent  ribs  closing 
the  intercostal  spaces. 

The  INTERCOSTALES  EXTERNI,  eleven  on  each  side,  commence 
posteriorly  at  the  tubercles  of  the  ribs,  and  advance  forwards  to 
the  costal  cartilages,  where  they  terminate  in  a  thin  aponeurosis 
which  is  continued  onwards  to  the  sternum.  Their  fibres  are 
directed  obliquely  downwards  and  inwards,  pursuing  the  same 
line  with  those  of  the  external  oblique  muscle  of  the  abdomen. 
They  are  thicker  than  the  internal  intercostals. 

The  INTERCOSTALES  INTERNI,  also  eleven  on  each  side,  com- 
mence anteriorly  at  the  sternum,  and  extend  backwards  as  far  as 
the  angles  of  the  ribs,  whence  they  are  prolonged  to  the  verte- 
bral column  by  a  thin  aponeurosis.  Their  fibres  are  directed 
obliquely  downwards  and  backwards,  and  correspond  in  direction 


INTERCOSTAL  NERVES.  355 

with  those  of  the  internal  oblique  muscle  of  the  abdomen.  The 
two  muscles  cross  each  other  in  the  direction  of  their  fibres. 

In  structure  the  intercostal  muscles  consist  of  an  admixture  of 
muscular  and  tendinous  fibres.  They  arise  from  the  two  lips  of 
the  lower  border  of  the  ribs,  the  external  from  the  outer  lip,  the 
internal  from  the  inner,  and  are  inserted  into  the  upper  border. 

When  the  anterior  wall  of  the  thorax  is  removed  for  the  purpose  of 
examining  the  contents  of  that  cavity,  a  muscle  will  be  found  upon  its 
inner  surface  connected  on  the  one  hand  with  the  border  of  the  sternum, 
and  on  the  other  with  the  cartilages  of  the  ribs ;  this  is  the  triangularis 
sterni.  In  making  the  dissection  necessary  for  the  examination  of  this 
muscle,  the  sternum  should  be  cut  across  on  a  level  with  the  lower  bor- 
der of  the  first  rib,  and  again  at  the  upper  border  of  the  articulation  of 
the  seventh ;  the  knife  should  then  be  carried  along  the  corresponding 
borders  of  these  ribs,  and  through  the  cartilages  and  intercostal  muscles 
as  far  outwards  as  possible.  The  segment  of  the  chest  included  by  the 
section  should  next  be  carefully  raised  and  the  cellular  tissue  divided, 
which  serves  to  connect  it  on  the  middle  line  with  the  mediastinum. 
The  triangularis  muscle  lying  against  the  cartilages  of  the  ribs  on  either 
side  of  the  sternum  may  now  be  seen  together  with  the  internal  mam- 
mary arteries,  and  the  surface  of  the  muscle  may  be  cleaned  by  the 
removal  of  some  cellular  tissue  and  fat. 

The  TRIANGULARIS  STERNI,  situated  upon  the  inner  wall  of  the 
front  of  the  chest,  arises  by  a  thin  aponeurosis  from  the  side  of 
the  sternum,  ensiform  cartilage,  and  sternal  extremities  of  the 
costal  cartilages ;  and  is  inserted  by  fleshy  digitations  into  the 
cartilages  of  the  third,  fourth,  fifth,  and  sixth  ribs,  and  often  into 
that  of  the  second. 

The  VESSELS  of  the  walls  of  the  chest  are  the  intercostal  arte- 
ries from  the  aorta,  and  the  internal  mammary  arteries,  branches 
of  the  subclavians. 

The  intercostal  arteries  lie  between  the  two  planes  of  intercostal 
muscle,  in  company  with  the  intercostal  vein  and  nerve,  the  former 
being  above  and  the  latter  below.  The  artery  is  placed  near  the 
lower  border  of  each  rib,  and,  at  about  the  middle  of  the  space, 
divides  into  two  branches,  which  run  along  the  borders  of  con- 
tiguous ribs,  and  in  the  front  of  the  chest  anastomose  with  the 
anterior  intercostal  branches  of  the  internal  mammary. 

If  the  external  intercostal  muscle  be  carefully  raised,  this  distribution 
of  the  intercostal  artery  may  be  seen,  and  at  the  same  time  the  intercostal 
nerve  by  which  the  artery  is  accompanied. 

The  INTERCOSTAL  NERVES  are  the  anterior  divisions  of  the  dorsal 
nerves.  The  nerve  takes  the  same  course  as  the  artery,  lying  by 
its  side,  but  iuferiorly  to  it  in  position.  Beyond  the  middle  of 
the  ribs,  the  nerve  is  embedded  in  the  substance  of  the  anterior 
intercostal  muscle,  and  then  gets  to  its  inner  surface  lying  in  con- 
tact with  the  pleura.  Near  the  sternum  the  nerve  pierces  the 
anterior  intercostal  and  pectoralis  major,  to  be  distributed  to  the 


356 


THE   DISSECTOR. 


integument  of  the  front  of  the  chest  under  the  name  of  anterior 
cutaneous.  Midway  between  the  vertebral  column  and  the 

Fig.  108.  THE  INTERNAL  ASPECT  OF  THE 

ANTERIOR  WALL  OP  THE  CHEST, 
SHOWING  THE  INTERNAL  MAM- 
MARY ARTERIES. — a.  The  internal 
surface  of  the  sternum,  b,  b.  The 
triangularis  sterni  muscles,  c,  c. 
The  intercostales  interni  muscles. 
d.  The  sterno-thyroid  muscles,  e,  e. 
The  cut  edge  of  the  diaphragm,  f. 
The  ensiform  cartilage ;  the  letter 
is  placed  on  the  linea  alba,  g,  g. 
The  transversalis  abdominis  muscle. 
h,  h.  The  posterior  wall  of  the 
sheath  of  the  recti  muscles,  i.  The 
arch  of  the  aorta,  k.  The  arteria 
innominata.  /.  The  common  caro- 
tid arteries,  m,  m.  The  subclavian 
arteries,  n,  n.  The  internal  mam- 
mary arteries.  On  the  left  side  the 
lymphatic  vessels  and  glands  in 
relation  with  the  internal  mam- 
mary vessels  are  seen,  o,  o.  Ante- 
rior intercostal  branches  which  in- 
osculate with  p,  p,  the  aortic  inter- 
costals.  q,  q.  Perforating  branches. 
r.  The  division  of  the  internal 
mammary  artery  into  superior  epi- 
gastric and  musculo-phrenic.  s,  s. 
The  musculo-phrenic  arteries,  t,  t. 
The  two  ascending  branches  of  the 
subclavian  artery,  vertebral,  and 

thyroid  axis,     v,  v.  The  superior  intercostal  arteries,  giving  off  the  profunda 

cervicis. 

sternum,  and  while  between  the  intercostal  muscles,  the  nerve 
gives  off  the  lateral  cutaneous  branch,  which  pierces  the  external 
intercostal  muscle  and  serratus  magnus,  and  divides  into  an  ante- 
rior and  posterior  twig  for  the  supply  of  the  integument  of  the 
side  of  the  thorax,  page  344. 

The  INTERNAL  MAMMARY  ARTERY,  a  branch  of  the  subclavian, 
passes  down  the  anterior  wall  of  the  chest,  by  the  side  of  the 
sternum,  and  resting  against  the  cartilages  of  the  ribs  and  inter- 
costal muscles,  to  the  sheath  of  the  rectus  abdominis  muscle, 
where,  under  the  name  of  superior  epigastric,  it  inosculates  with 
the  epigastric  artery,  a  branch  of  the  external  iliac.  It  is  covered 
by  the  pleura  and  triangularis  sterni  muscle,  and  accompanied  by 
the  internal  mammary  veins  and  a  chain  of  lymphatic  glands. 

The  branches  of  the  internal  mammary  artery  within  the  chest 
are  as  follows  : — 

The  comes  nervi  phrenici,  a  long  and  slender  branch  given  off 


SHOULDER  AND  SCAPULA.  357 

by  the  artery  as  it  enters  the  chest,  descends  by  the  side  of  the 
phrenic  nerve  to  the  diaphragm. 

Several  small  mediastinal  and  pericardiac  branches  distributed 
to  the  anterior  mediastinum,  pericardium,  thyrnus  gland,  and 
triangularis  sterni  muscle. 

Anterior  intercostal*,  which  supply  the  intercostal  muscles  of 
the  front  of  the  chest,  and  inosculate  with  the  aortic  intercostals  ; 
to  each  space  there  are  two  arteries  which  run  along  the  borders 
of  the  rib.  Besides  supplying  the  intercostal  muscles,  they  send 
branches  to  the  pectoral  muscles  and  mammary  gland. 

Perforating  arteries  (mammary),  which  pass  forwards  to  the 
front  of  the  chest  through  the  first  six  intercostal  spaces ;  they 
then  turn  outwards,  and  after  giving  some  branches  to  the  front 
of  the  sternum,  are  distributed  to  the  pectoral  muscles  and  mam- 
mary gland.  Those  intended  for  the  mammary  gland  are  of 
larger  size  than  the  rest. 

The  musculo-phrenic  artery,  which  proceeds  from  the  internal 
mammary  at  the  interspace  between  the  sixth  and  seventh  ribs, 
and  passes  downwards  and  outwards  over  the  cartilages  of  the 
false  ribs  to  the  last  intercostal  space.  It  pierces  the  diaphragm 
at  the  attachment  of  that  muscle  to  the  eighth  rib,  and  sends 
branches  to  its  muscular  structure,  and  others  to  the  intercostal 
spaces  of  the  false  ribs. 

The  student  must  now  proceed  to  the  examination  of  the  contents  of 
the  thorax,  and  for  a  description  of  the  viscera  of  that  cavity  may  turn 
to  Chapter  VI.  After  the  thorax  has  been  studied,  the  subject  is  to  be 
turned,  and  the  muscles  of  the  back  dissected  and  examined ;  the  de- 
scription of  these  muscles  is  contained  in  Chapter  X.  We  may  now 
suppose  that  these  dissections  have  been  completed,  and  the  student  is 
anxious  to  continue  the  dissection  of  the  arm.  For  this  purpose  he  must 
saw  the  clavicle  across  at  about  its  middle,  and  cut  away,  at  a  short  dis- 
tance from  their  insertion,  those  muscles  of  the  scapula  and  shoulder 
which  still  retain  the  arm  in  connection  with  the  body.  These  muscles 
are,  the  trapezius,  levator  anguli  scapula  and  omohyoideus  above  ;  rhom- 
boideus  minor  and  major,  behind  ;  latissimus  dorsi  below;  and  serratus 
magnus  in  front.  The  above  muscles  may  now  be  examined  more  atten- 
tively in  reference  to  their  attachments,  and  the  shoulder  placed  in  a 
favorable  position  for  the  dissection  of  its  proper  muscles,  beginning  with 
the  deltoid. 

Dissection  of  the  Shoulder  and  Scapula. 

Acromial  Region. 

The  integument  should  now  be  raised  from  off  the  deltoid 
muscle,  beginning  at  its  anterior  border,  and  reflecting  it  out- 
wards as  far  as  the  base  of  the  scapula,  and  downwards  to  the 
insertion  of  the  deltoid  and  the  inferior  angle  of  the  scapula. 

In  the  superficial  fascia  covering  the  upper  part  of  the  muscle 
will  be  found  some  nervous  filaments,  supra-acromiales,  from  the 


358  THE   DISSECTOR. 

cervical  plexus  ;  and  spreading  over  the  lower  half  of  the  muscle 
from  its  posterior  border,  several  cutaneous  branches  of  the  cir- 
cumflex nerve.  Along  its  anterior  border  lie  the  cephalic  vein 
and  accompanying  branch  of  the  thoracica  acromialis  artery. 

The  deep  fascia  covering  the  deltoid  muscle,  like  that  of  its 
analogue,  the  glutens  maximus,  is  thin,  and  the  muscle  beneath 
coarse,  and  made  up  of  numerous  fasciculi  separated  by  tendinous 
intersections.  The  deep  fascia  must  be  dissected  off  in  the  course 
of  the  muscular  fibres. 

The  DELTOID  muscle  (A,  delta ;  ftSoj,  resemblance)  arises  from 
the  outer  third  of  the  clavicle,  from  the  acromion  process,  and 
from  the  whole  length  of  the  spine  of  the  scapula.  The  fibres 
from  this  broad  origin  converge  to  the  middle  of  the  outer  side 
of  the  humerus,  where  they  are  inserted  into  a  rough  triangular 
elevation. 

The  deltoid  muscle  may  now  be  cut  away  from  its  extensive  origin  and 
turned  down.  In  so  doing  the  posterior  circumflex  vessel  and  circumflex 
nerve  will  be  found  connected  by  numerous  branches  to  its  under  surface, 
and  a  large  bursa  over  the  head  of  the  humerus  will  be  exposed.  The 
vessels  and  nerves  should  be  cleaned,  and  the  cellular  tissue  removed 
from  the  tendons  and  muscles  which  are  now  brought  into  view.  In  front 
will  be  seen  the  broad  tendon  of  the  subscapularis  ;  crossing  the  head  of 
the  bone  that  of  the  supra-spinatus  conjoined  externally  with  the  infra- 
spinatus,  and  below  the  latter  the  teres  minor.  The  three  latter  muscles 
proceeding  from  the  dorsum  of  the  scapula,  as  well  as  the  subscapularis 
from  its  ventral  surface,  should  now  be  dissected  and  cleaned.  To  see 
the  supra-spinatus  it  will  be  further  necessary  to  divide  the  trapezius 
muscle  from  its  insertion  into  the  upper  border  of  the  spine  of  the  scapula 
and  from  the  clavicle.  The  circumflex  vessels  and  nerve  which  impede 
this  dissection  should  now  be  studied  and  cut  across. 

The  POSTERIOR  CIRCUMFLEX  ARTERY,  proceeding  from  the  lower 
part  of  the  axillary,  reaches  the  under  surface  of  the  deltoid,  after 
passing  through  a  quadrangular  interval,  bounded  by  the  teres 
minor  above,  teres  major  below,  the  neck  of  the  humerus  in  front, 
and  the  long  head  of  the  triceps  behind.  It  supplies  branches 
to  these  muscles  in  its  course ;  is  then  distributed  to  the  deltoid 
and  shoulder-joint,  and  inosculates  with  the  anterior  circumflex, 
which,  now  that  the  deltoid  is  turned  down,  may  be  seen  winding 
around  the  neck  of  the  humerus  from  the  front. 

The  CIRCUMFLEX  NERVE  takes  the  same  course  as  the  posterior 
circumflex  artery,  from  the  lower  part  of  the  axilla,  and  having 
reached  the  back  of  the  humerus,  separates  into  an  upper  and  a 
lower  division ;  the  upper  division,  continuing  onwards  beneath 
the  deltoid,  is  distributed  to  the  anterior  part  of  that  muscle  ;  the 
lower  division  sends  a  branch  (remarkable  for  a  gangliform  swell- 
ing) to  the  teres  minor,  several  branches  to  the  posterior  part  of 
the  deltoid,  and  mounting  over  the  border  of  the  muscle  becomes 
cutaneous,  supplying  the  integument  over  its  lower  half  by  means 


POSTERIOR   SCAPULAR  REGION. 


359 


of  several  filaments.  Besides  its  muscular  and  cutaneous  branches, 
the  trunk  of  the  nerve  gives  off  an  articular  branch,  which  enters 
the  shoulder-joint  at  its  posterior  and  under  part. 

Posterior  Scapular  Region. 
The  muscles  of  this  region  are  the — 

Supra-spinatus,  Teres  minor, 

Infra-spinatus,  Teres  major. 

The  supra-spinatus  muscle  is  covered  in  by  a  strong  fascia,  which  must 

be  removed  in  order  to  bring  the  muscle 

into  view.     At  an  after  part  of  the  dissec-  Fig.  109. 

tion,  when  the  ligaments  have  been  ex- 
amined, the  acromion  process  may  be  sawn 

through,  in  order  to  lay  bare  the  entire  ex- 
tent of  the  muscle ;  this  proceeding  is  not, 

however,  indispensable.    In  the  preparation 

of  the  supra-spinatus,  the  student  should 

direct  his  attention  to  the  boundaries  of  the 

hollow  in  which  the  muscle  is  contained. 

To  the  upper  border  of  the  scapula  he  will 

find   inserted  the   small  muscle  from  the 

neck,  omohyoideus.  In  front  of  the  attach- 
ment of  this  muscle  is  the  transverse  liga- 
ment which  converts  the  notch  in  the  upper 

border  of  the  scapula  into  a  foramen,  the 

supra-scapular  nerve  enters  the  supra-spi- 

nous  fossa  through  this  foramen,  while  the 

supra-scapular  artery  passes  over  it.   To  the 

angle  of  the  scapula,  and  that  portion  of  the 

posterior  border  which  corresponds  with  the 

supra-spinatus  fossa,  is  attached  the  levator 

anguli  scapulae,  and  from  the  upper  border 

of  the  spine  of  the  scapula  the  trapezius  has 

already  been  removed. 

The  SUPRA-SPINATUS  muscle  arises 
from  the  supra-spinous  fossa,  the  spine 
of  the  scapula  and  deep  fascia  ;  and  is 
inserted  into  the  uppermost  depression 
on  the  greater  tuberosity  of  the  hu- 
merus. 

The  INFRA-SPINATUS  muscle  arises 
from  the  whole  extent  of  the  infra-spi- 
nous  fossa,  excepting  a  small  portion 

near  the  neck  of  the  bone,  from  the  scapular  head.  3.  its  internal, 
spine  of  the  scapula  and  from  its  in-  or  short  head.  4.  The  oie- 
vesting  fascia.  The  muscle  is  inserted  T?"  r^usl^e^The  capsuifr 
into  the  middle  depression  on  the  ligament  of  the  shoulder-joint, 
greater  tuberosity  of  the  humerus,  its 

tendon  being  blended  with  that  of  the  supra-spinatus  above,  and 
the  teres  minor  below. 


A  POSTERIOR  VIEW  OF  THE 
UPPEB  A«*>  SHOWING   THE 


360  THE   DISSECTOR. 

In  studying  the  connections  of  this  muscle,  the  student  should  direct 
his  attention  to  a  muscle  attached  to  the  posterior  border  of  the  scapula, 
the  rhomboideus  major,  and  above  this  the  small  band  of  muscle,  rhom- 
boideus  minor,  which  is  attached  to  that  portion  of  the  border  which  cor- 
responds with  the  base  of  the  triangular  expansion  of  the  spine  of  the 
scapula  over  which  the  trapezius  glides.  The  next  two  muscles  are  con- 
nected with  the  lower  or  anterior  border  of  the  scapula. 

The  TERES  MINOR  (teres,  round)  muscle  arises  from  the  poste- 
rior surface  of  the  lower  border  of  the  scapula  for  about  the 
middle  third  of  its  extent.  It  is  closely  connected  with  the  lower 
border  of  the  preceding  muscle,  and  is  inserted  into  the  inferior 
depression  of  the  greater  tuberosity  of  the  humerus. 

The  tendons  of  the  three  preceding  muncles,  with  that  of  the 
subscapularis,  are  in  immediate  contact  with  the  joint,  and  form 
part  of  its  ligamentous  capsule,  thereby  preserving  the  solidity  of 
the  articulation.  They  are  therefore  the  structures  most  fre- 
quently ruptured  in  dislocation  of  the  shoulder-joint  with  violence. 

The  TERES  MAJOR  muscle  arises  from  the  dorsal  surface  of  the 
inferior  angle  of  the  scapula,  and  from  its  inferior  border.  It  is 
inserted  conjointly  with  the  tendon  of  the  latissimus  dorsi  into  the 
posterior  bicipital  ridge  of  the  humerus.  At  its  origin  this 
muscle  is  covered  by  the  latissimus  dorsi,  but  the  latter  shortly 
afterwards  curves  around  its  lower  border,  and  becomes  placed 
in  front.  The  two  tendons  at  their  insertion,  one  lying  behind 
the  other,  are  separated  by  a  bursa. 

The  VESSELS  and  NERVES  of  the  posterior  scapular  region  are 
the  supra-scapular  artery  and  nerve,  and  the  dorsalis  scapulae 
branch  of  the  subscapular  artery. 

The  supra-scapular  artery,  a  branch  of  the  thyroid  axis  of  the 
subclavian,  crosses  the  root  of  the  neck  to  the  superior  border  of 
the  scapula ;  it  then  passes  over  the  transverse  ligament  of  the 
supra-scapular  notch,  and  enters  the  supra-spinous  fossa,  getting 
beneath  the  supra-spinatus  muscle.  After  giving  branches  to 
that  muscle  and  the  shoulder-joint,  the  artery  passes  in  front  of 
the  spine  of  the  scapula  into  the  infra-spinous  fossa,  where  it 
inosculates  with  dorsalis  scapulae  and  posterior  scapular. 

The  supra-scapular  nerve,  a  branch  of  the  brachial  plexus, 
enters  the  supra-spinous  fossa  through  the  supra-scapular  notch, 
and,  after  supplying  the  muscle  and  shoul'der-joint,  passes  with 
the  artery  into  the  infra-spinous  fossa,  and  is  distributed  to  the 
infra-spinatus  muscle. 

The  dorsales  scapula  artery,  a  branch  of  the  subscapular,  curves 
around  the  inferior  border  of  the  scapula  through  the  triangular 
space  bounded  by  the  teres  minor  above,  teres  major  below,  and 
long  head  of  the  triceps  in  front,  and  passing  beneath  the  teres 
minor  enters  the  infra-spinous  fossa,  and  is  distributed  to  its 
muscle,  inosculating  with  the  termination  of  the  supra-scapular 


ANTERIOE   SCAPULAE  REGION. 


361 


Fig.  110. 


artery.  While  in  the  triangular  space  it  gives  off  a  branch  which 
runs  between  the  teres  minor  and  major  to  the  angle  of  the  sca- 
pula, and  inosculates  with  the  posterior  scapular  artery. 

The  posterior  circumflex  artery  and  nerve  which  supply  the 
teres  muscles  will  be  found  in  the  quad- 
rangular space  in  front  of  the  long  head 
of  the  triceps ;  and  along  the  posterior 
border  of  the  scapula  may  be  seen  the  twigs 
of  distribution  of  another  scapular  artery, 
the  posterior  scapular. 

The  posterior  scapular  artery  is  a  branch 
of  the  transversaliscolli  of  the  subclavian  ; 
it  descends  along  the  posterior  border  of 
the  scapula  under  cover  of  the  levator  an- 
guli  scapulae  and  rhomboid  muscles  to  the 
inferior  angle.  In  its  course  it  gives 
branches  to  both  surfaces  of  the  scapula, 
and  inosculates  in  the  infra-spinous  fossa 
with  supra-scapular  and  dorsalis  scapulae 
arteries,  and  at  its  termination  with  the 
subscapular  artery. 

Anterior  Scapular  Region. 

The  only  muscle  situated  in  the  anterior 
scapular  region  is  the  subscapularis,  which  is 
bound  down  by  a  thin  process  of  aponeurotic 
fascia.  To  this  aspect,  along  the  posterior 
border  of  the  scapula,  is  attached  the  serratus 
magnus  muscle.  The  vessels  and  nerves  of  the 
region  are  the  subscapular  ;  the  posterior  sca- 
pular artery  may  be  seen  uncovered  by  muscle 
lying  along  its  posterior  border. 

The  SUBSCAPULARIS  muscle  arises  from 
the  whole  of  the  under  surface  of  the 

scapula  excepting  the  superior  and  inferior  ins  upwards  to  the  scapular 
angles,  and  terminates  by  a  broad  and  eoicL^roS^iigamJnt* 
thick  tendon,  which  is  inserted  into  the  passing  outwards  to  the 
lesser  tuberosity  of  the  humerus,  and  by  acromion.  4.  The  subsca- 
muscular  fibres  into  the  surface  of  bone 
immediately  below  that  process.  The 
substance  of  the  muscle  is  traversed  by 
several  intersecting  membranous  layers, 
from  which  muscular  fibres  arise,  the  in- 
tersections being  attached  to  the  ridges 
on  the  surface  of  the  scapula.  Its  tendon  forms  part  of  the  capsule 
of  the  joint,  glides  over  a  large  bursa  which  separates  it  from  the 
31 


THE  MUSCLES  OP  THE 
ANTERIOR  ASPECT  OF  THK 
UPPER  ARM. — 1.  The  co- 
racoid  process  of  the  scapu- 
la. 2.  Thecoraco-clavicular 
ligament  (trapezoid),  pass- 


5.  The 
teres  major.  6.  The  cora- 
co-brachialis.  7.  The  bi- 
8.  The  upper  end  of 


internal  head  of  the  triceps. 


362  THE   DISSECTOR. 

base  of  the  coracoid  process,  and  is  lined  by  a  prolongation  of 
the  synovial  membrane  of  the  articulation. 

The  SUBSCAPULAR  ARTERY,  lying  along  the  lower  border  of  the 
scapula,  sends  branches  to  the  subscapularis  muscle,  and  inoscu- 
lates with  the  posterior  scapular.  A  branch  (infra-scapular)  from 
the  dorsalis  scapulae  passes  beneath  the  muscle,  and  on  the  surface 
of  the  bone,  inosculates  with  the  supra-scapular  above,  and  the 
posterior  scapular  behind. 

The  subscapular  nerves  have  been  already  described ;  page  353. 

Anterior  Brachial  Region. 

Having  placed  the  arm  in  a  convenient  position  for  dissection,  an  in- 
cision should  be  made  through  the  integument,  along  the  middle  of  the 
biceps  muscle,  to  about  three  inches  below  the  elbow,  and  bounded  at  its 
extremity  by  a  transverse  incision.  The  integument  is  next  to  be  dis- 
sected carefully  back,  and  the  superficial  fascia  exposed.  The  superficial 
vessels  and  nerves  are  then  to  be  sought  for  in  the  superficial  fascia,  and 
examined. 

Lying  along  the  outer  side  of  the  convexity  formed  by  the 
biceps  is  a  large  vein,  the  cephalic,  which  may  be  traced  upwards 
to  the  interspace  between  the  deltoid  and  pectoralis  major,  and 
downwards  to  the  outer  side  of  the  elbow-joint;  below  the  elbow- 
joint  it  is  the  radial  vein.  On  the  inner  side  of  the  convexity  of 
the  biceps  is  another  large  vein,  basilic,  which  at  the  elbow  is 
formed  by  the  union  of  the  anterior  and  posterior  ulnar  veins. 
In  the  middle  line  of  the  forearm,  between  the  radial  and  ulnar 
veins,  is  the  median  vein,  which  just  below  the  elbow  divides  into 
two  brandies,  one  to  join  the  cephalic  vein,  median  cephalic,  and 
one  to  the  basilic  vein,  median  basilic. 

Behind  the  cephalic  vein,  and  commencing  at  the  middle  of  the 
arm,  are  two  cutaneous  branches  from  the  musculo-spiral  nerve  ; 
and  in  the  groove  to  the  outer  side  of  the  tendon  of  the  biceps  at 
the  bend  of  the  elbow  the  external  cutaneous  nerve  pierces  the 
deep  fascia.  On  the  inner  side  of  the  arm  immediately  below 
the  axilla,  may  be  found  the  intercosto-humeral  nerve  and  a  cuta- 
neous branch  of  the  musculo-spiral ;  at  about  the  middle  of  the 
upper  arm  the  internal  cutaneous  nerve  pierces  the  fascia  and  runs 
down  the  arm  by  the  side  of  the  basilic  vein  ;  and  at  the  lower 
third  of  the  upper  arm,  and  behind  the  preceding,  is  the  lesser 
internal  cutaneous  nerve,  or  nerve  of  Wrisberg. 

CUTANEOUS  VEINS. — The  median  vein  is  so  named  from  its 
position  in  the  middle  of  the  forearm.  It  receives  the  returning 
blood  from  the  front  of  the  hand  and  forearm,  and  near  the 
elbow  forms  a  trunk  of  moderate  size,  which  is  increased  by  a 
communicating  branch,  9,  from  the  deep  veins.  Just  below  the 
bend  of  the  elbow,  the  median  divides  into  two  branches — the 
median  basilic  and  median  cephalic. 


ANTERIOR  BRACHIAL  REGION. 


363 


Fig.  111. 


The  median  basilic  vein,  the  larger  of  the  two,  passes  obliquely 
inwards  along  the  border  of  the  biceps,  and  unites  with  the  com- 
mon trunk  of  the  ulnar  veins  to  form  the  basilic  vein.  It  crosses 
the  braci'ial  artery,  being  separated  from  it  by  the  deep  fascia, 
which  is  here  strengthened  by  an  aponeurotic  slip,  given  off  by 
the  edge  of  the  tendon  of  the  biceps.  The  vein  has  one  or  two 
filaments  of  the  internal  cutaneous  nerve  passing  in  front,  and 
others  passing  behind  it.  The  relations  of  this  vein  should  be 
carefully  studied,  in  reference  to  the  operation  of  bleeding,  this 
being  the  vein  the  best  suited  for  the  purpose. 

The  median  cephalic  vein,  longer  and 
somewhat  smaller  than  the  preceding, 
inclines  outwards  in  the  groove  between 
the  biceps  and  the  supinator  longus,  to 
unite  with  the  radial  vein,  and  form  the 
cephalic  vein.  The  branches  of  the  ex- 
ternal cutaneous  nerve  pass  behind  it. 
From  the  depth  of  the  groove  in  which 
this  vein  is  placed,  and  its  smaller  size, 
it  is  not  usually  selected  for  the  operation 
of  bleeding. 

In  the  best  performed  operations  on 
these  veins,  inconvenience  sometimes 
arises  from  the  wound  or  division  of  the 
cutaneous  nerves.  This  accident  is  most 
likely  to  occur  in  opening  the  median 
basilic,  because  the  internal  cutaneous 
nerves  pass  in  front  of  that  vein  ;  the  ex-, 
ternal  cutaneous  nerves  being  behind  the 
median  cephalic  vein.  The  results  of 
such  an  accident  may  be  slight  or  serious, 
in  proportion  to  the  dexterity  of  the 
operator,  or  the  condition  of  the  lancet. 
A  sharp  blade  and  a  clean  wound  can 
never  do  amiss. 

THE  SUPERFICIAL  ANATOMY  OF  THE  BEND  OF  THE  ELBOW. — 1.  The  radial 
vein.  2.  The  cephalic  vein.  3.  The  anterior  ulnar  vein.  4.  The  posterior  ulnar 
vein.  5.  The  common  ulnar  vein.  6.  The  basilic  vein.  7.  The  point  at  which 
the  basilic  vein  pierces  the  fascia.  8.  The  median  vein.  9.  The  communi^ 
cation  between  the  deep  veins  of  the  forearm  and  the  median.  10.  The  median 
cephalic  vein.  11.  The  median  basilic  vein,  12.  A  slight  convexity  of  the 
deep  fascia,  formed  by  the  brachial  artery.  13.  The  slip  of  fascia  derived  from 
the  tendon  of  the  biceps,  which  separates  the  median  basilic  vein  from  the  bra- 
chial artery.  14.  The  external  cutaneous  nerve,  piercing  the  fascia  and  dividing 
into  two  branches,  which  pass  behind  the  median  cephalic  vein.  15.  The  inter- 
nal cutaneous  nerve  dividing  into  branches,  which  pnss  in  front  of  the  medirn 
basilic  vein.  16.  The  nerve  of  Wrisberg.  17.  The  spiral  cutaneous  nerve, 
branch  of  the  m use ulo -spiral  nerve. 


364  THE  DISSECTOR. 

Occasionally  the  median  basilic  is  completely  transfixed,  and 
the  process  of  fascia  derived  from  the  edge  of  the  biceps  tendon 
injured.  Inflammation  may  supervene  and  be  followed  by  con- 
traction of  the  fascia,  causing  great  pain  and  deformity  to  the 
patient. 

But  this  is  not  all ;  the  brachial  artery  is  sometimes  wounded 
also.  The  lancet  has  transfixed  the  entire  cylinder  of  the  vein, 
the  process  of  fascia,  and  the  coats  of  the  artery.  The  conse- 
quences of  this  accident  cannot  be  too  strongly  impressed  upon 
the  student's  recollection,  they  are  as  follows  : — 

1.  "  False  aneurism  is  the  most  common  form  of  disease  fol- 
lowing the  accidental  wound  of  the  artery  at  the  bend  of  the 
arm."1     In  this  case  the  blood  rushing  from  the  wounded  vessel 
forms  for  itself  a  sac  by  the  condensation  of  the  surrounding 
tissues. 

2.  Aneurismal  varix  is  the  accident  next  in  frequency:  "the 
coats  of  the  vein  and  artery  become  firmly  agglutinated,"  and 
"the  arterial  blood  is  poured  into  the  vein  at  each  contraction  in 
a  small  and  forcible  stream,  occasioning  a  peculiar  shrill  sound." 

3.  The  third  variety,  "  Varicose  aneurism,"  is  rare.     It  con- 
sists in  the  formation  of  a  false  aneurism  between  the  artery  and 
vein,  and  communicating  with  both. 

Thus  it  may  be  shown  that  this  operation,  so  apparently  simple 
and  easy  of  execution,  that  is  constantly  intrusted  to  the  hands 
of  the  tyro  apprentice,  often  before  he  has  ever  opened  a  manual 
of  anatomy,  is  attended  with  dangers,  if  caution  be  not  used, 
equal  to  those  of  many  of  the  greater  operations  of  surgery.  We 
therefore  advise  the  dissector  not  to  pass  hastily  over  this  region, 
but  consider  well  its  relations  and  appliances.  If  other  reasons 
for  his  attention  were  needed,  he  should  recollect  that  every  man 
is  a  judge  of  so  common  a  proceeding. 

The  radial  vein  collects  the  venous  blood  from  the  thumb  and 
outer  aspect  of  the  hand  and  forearm;  it  is  often  of  small  size. 
Its  junction  with  the  median  cephalic  constitutes  the  cephalic 
vein. 

The  cephalic  vein  (xf^>a^r>,  the  head)  ascends  the  outer  side  of 
the  arm  to  the  groove  between  the  pectoralis  major  and  deltoid, 
where  it  is  in  relation  with  the  descending  branch  of  the  thoracica 
acromialis  artery,  and  terminates  beneath  the  clavicle  in  the  axil- 
lary vein.  A  large  communicating  branch  sometimes  crosses 
the  clavicle  between  the  external  jugular  and  this  vein,  which 
gives  it  the  appearance  of  being  derived  directly  from  the  head — 
hence  its  appellation. 

1  The  passages  between  inverted  commas  are  quotations  from  Liston's 
"  Practical  Surgery." 


CUTANEOUS   NERVES.  365 

The  ulnar  veins,  anterior  and  posterior,  unite  near  the  bend  of 
the  elbow  to  form  a  common  ulnar  trunk,  and  the  latter,  after 
receiving  the  median  basilic,  becomes  the  basilic  vein. 

The  basilic  vein  (J3a<jaix6j,  royal,  or  principal)  ascends  from 
the  comraom  ulnar  vein  formed,  by  the  two  preceding,  along  the 
inner  side  of  the  upper  arm,  and  near  its  middle  pierces  the  fascia ; 
it  then  passes  upwards  to  the  axilla,  and  becomes  the  axillary 
vein.  In  its  course  it  lies  to  the  inner  side  of  the  brachial  artery. 

The  lymphatic  vessels  of  the  upper  arm  follow  the  course  of  the 
basilic  and  cephalic  veins,  those  accompanying  the  former  being 
the  most  numerous.  Just  above  the  elbow,  to  the  inner  side  of 
the  basilic  vein,  may  be  found  a  lymphatic  gland. 

CUTANEOUS  NERVES. — The  external  cutaneous  nerves  are  de- 
rived from  the  musculo-spiral  and  musculo-cutaneous.  The  cuta- 
neous  branches  of  the  musculo-spiral,  two  in  number,  pierce  the 
deep  fascia,  the  one  (upper}  just  below  the  insertion  of  the  deltoid, 
the  other  (lower)  at  about  the  middle  of  the  upper  arm.  The 
upper  branch  descends  by  the  side  of  the  cephalic  vein,  and  sup- 
plies the  integument  as  far  as  the  elbow.  The  lower  branch 
passes  down  in  front  of  the  elbow,  and  along  the  outer  side  of 
the  forearm  to  the  back  of  the  wrist;  supplying  the  integument 
in  its  course. 

The  cutaneous  portion  of  the  musculo-cutaneous  nerve,  emerging 
from  beneath  the  tendon  of  the  biceps,  pierces  the  deep  fascia  at 
the  bend  of  the  elbow,  and  passing  behind  the  median  cephalic 
vein,  divides  into  two  branches,  which  are  distributed  to  the  outer 
side  of  the  forearm,  as  far  as  tjhe  hand. 

The  internal  cutaneous  nerves  are  derived  from  the  internal 
cutaneous,  the  lesser  internal  cutaneous,  the  intercosto-humeral, 
and  the  musculo-spiral. 

The  internal  cutaneous  nerve  pierces  the  fascia  by  the  side  of 
the  basilic  vein  at  about  the  middle  of  the  upper  arm,  and  divides 
into  two  branches,  external  and  internal.  The  external  branch 
passes  in  front  of,  and  sometimes  behind,  the  median  basilic  vein, 
and  along  the  inner  side  of  the  forearm  to  the  wrist.  The  inter- 
nal branch  passes  inwards  behind  the  internal  condyle,  and  after 
giving  filaments  to  the  region  of  the  olecranon,  Descends  along 
the  forearm  to  the  wrist.  While  in  the  axilla,  the  internal  cuta- 
neous nerve  gives  off  a  cutaneous  branch,  which  pierces  the 
fascia,  and  descends  along  the  inner  side  of  the  arm  to  the  elbow. 

The  lesser  internal  cutaneous  nerve,  or  nerve  of  Wrisberg, 
passes  down  the  upper  arm,  lying  to  the  inner  side  of  the  brachial 
vessels  and  internal  cutaneous  nerve,  and  pierces  the  deep  fascia 
at  about  the  middle  of  its  posterior  aspect,  to  be  distributed  to 
the  integument  of  the  lower  third  of  the  upper  arm,  as  far  as  tfte 
olecranon.  While  in  the  axilla,  the  nerve  of  Wrisberg  connnu  • 

31* 


THE   DISSECTOR. 

nicates  with  the  intercosto-humeral  nerve,  and  sometimes  its  place 
is  taken  by  the  latter. 

The  intercosto-humeral  nerve,  the  lateral  cutaneous  branch  of 
the  second  intercostal  nerve,  communicates  with  the  nerve  of 
Wrisberg  in  the  axilla,  and,  piercing  the  fascia,  is  distributed 
to  the  integument  of  the  inner  and  posterior  aspect  of  the  upper 
half  of  the  upper  arm.  Besides  communicating  with  the  nerve 
of  Wrisberg,  one  of  its  branches  unites  with  the  internal  cutane- 
ous branch  of  the  musculo-spiral  nerve. 

The  internal  cutaneous  branch  of  the  musculo-spiral  nerve  passes 
backwards  beneath  the  intercosto-humeral  nerve,  and,  after  com- 
municating with  one  of  its  branches,  is  distributed  to  the  integu- 
ment of  the  middle  of  the  posterior  aspect  of  the  upper  arm,  as 
far  as  the  olecranon. 

The  DEEP  FASCIA  of  the  upper  arm  is  continuous  above  with 
the  thin  aponeurosis  which  covers  in  the  pectoralis  major  and 
deltoid,  and  forms  the  lower  boundary  of  the  axilla.  It  receives, 
at  its  upper  part,  an  addition  of  fibres  from  the  tendons  of  the 
pectoralis  major,  teres  major,  and  latissiraus  dorsi,  sends  inwards 
sheaths  for  the  muscles,  and  is  attached  on  either  side  to  the 
condyloid  ridges  and  condyles ;  inferiorly,  it  is  continuous  with 
the  fascia  of  the  forearm,  and  at  the  elbow  receives  a  strong  band 
of  fibres  from  the  inner  border  of  the  tendon  of  the  biceps.  The 
attachment  of  the  deep  fascia  to  the  condyloid  ridges  constitutes 
the  intermuscular  septa,  between  the  muscles  of  the  anterior  and 
posterior  brachial  region. 

The  deep  fascia  should  be  laid  open  by  means  of  an  incision  made 
along  the  middle  of  the  biceps  to  the  bend  of  the  elbow,  and  crossed  at 
that  point  by  a  transverse  incision.  The  fascia  should  then  be  reflected 
to  either  side,  when  the  muscles,  vessels,  and  nerves  of  the  anterior  bra- 
chial region  will  be  brought  into  view. 

The  MUSCLES  of  the  anterior  brachial  region  are  three  in  num- 
ber; namely,  the — 

Coraco-brachialis, 
Biceps, 

Brachialis  anticus. 

The  CORACO-BRACHIALIS — a  na'me  composed  of  its  points  of 
origin  and  insertion — arises  from  the  coracoid  process  in  common 
with  the  short  head  of  the  biceps,  and  is  inserted  into  a  rough 
line  on  the  inner  side  of  the  middle  of  the  humerus.  The  muscle 
is  pierced  from  within  outwards  by  the  musculo-cutaneous  nerve. 
The  BICEPS  (bis — xt$a?.ai,  two  heads)  arises  by  two  tendons, 
one  the  short  head,  from  the  coracoid  process  in  common  with 
the  coraco-brachialis ;  the  other,  the  long  head,  from  the  upper 
part  of  the  glenoid  cavity.  The  muscle  is  inserted  by  a  rounded 


BEACHIALIS-ANTICUS — TRICEPS.  367 

tendon  into  the  back  part  of  the  tubercle  of  the  radius.  The 
long  head,  a  long  slender  tendon,  passes  through  the  capsular 
ligament  of  the  shoulder-joint  inclosed  in  a  sheath  of  the  synovial 
membrane ;  after  leaving  the  cavity  of  the  joint  it  is  lodged  in 
the  deep  groove  that  separates  the  two  tuberosities  of  the  hume- 
rus,  the  bicipital  groove.  A  small  synovial  bursa  is  interposed 
between  the  tendon  of  insertion  and  the  tubercle  of  the  radius. 
At  the  bend  of  the  elbow,  the  tendon  of  the  biceps  gives  off  from 
its  inner  side  a  tendinous  band  (Fig.  Ill,  13),  which  protects  the 
brachial  artery,  and  is  continuous  with  the  fascia  of  the  forearm. 
To  see  the  next  muscle,  the  biceps  must  be  drawn  aside  ;  it  covers  the 
entire  breadth  of  the  humerus  at  its  lower  part,  and  extends  for  a  short 
distance  beyond  the  biceps  on  either  side. 

The  BRACHIALIS  ANTicus  muscle  arises  by  two  fleshy  serrations 
from  the  depressions  on  either  side  of  the  insertion  of  the  deltoid, 
from  the  anterior  surface  of  the  humerus,  and  from  the  inner 
intermuscular  septum.  Its  fibres  converge  to  be  inserted  into 
the  coronoid  process  of  the  ulna,  between  two  processes  of  the 
flexor  longus  digitorum. 

As  some  convenience  will  arise  to  the  student  from  possessing  a  know- 
ledge of  the  triceps  muscle,  the  muscle  of  the  posterior  brachial  region, 
before  studying  the  brachial  artery  and  nerves,  he  may  now  turn  the 
arm  and  bring  the  muscle  into  view  by  detaching  the  deep  fascia  in  the 
manner  practised  for  the  anterior  muscles. 

The  TRICEPS,  or  triceps  extensor  cubiti  muscle  (tptig  xtQaial, 
three  heads),  arises  by  three  heads — external,  middle,  and  internal. 

The  external  head  arises  from  the  whole  length  of  the  external 
and  posterior  aspect  of  the  humerus,  from  the  insertion  of  the  teres 
minor  at  the  greater  tuberosity  to  the  external  condyle,  and  also 
from  the  external  intermuscular  septum.  The  internal  head  arises 
from  the  inner  and  posterior  aspect  of  the  humerus,  from  the  in- 
sertion of  the  teres  major  to  the  internal  condyle,  and  from  the 
internal  intermuscular  septum.  The  middle  or  long  head  arises 
from  the  lower  part  of  the  head  and  adjoining  part  of  the  border 
of  the  scapula,  to  the  extent  of  about  an  inch.  The  three  heads, 
passing  downwards  in  different  directions,  unite  to  form  a  broad 
muscle,  which  is  inserted  into  the  olecranon  process  of  the  ulna, 
and  sends  an  expansion  to  the  deep  fascia  of  the  forearm.  A 
small  bursa  is  situated  between  the  tendon  of  the  muscle  and  the 
upper  part  of  the  olecranon. 

ACTIONS. — We  may  now  inquire  into  the  actions  of  the  musctes  of  the 
shoulder  and  upper  arm.  The  pectoralis  major  draws  the  arm  against 
the  thorax,  while  its  upper  fibres  assist  the  upper  part  of  the  trapezius 
in  raising  the  shoulder,  as  in  supporting  weights.  The  lower  fibres  de- 
press the  shoulder  with  the  aid  of  the  latissimus  dorsi.  Taking  its 
fixed  point  from  the  shoulder,  the  pectoralis  major  assists  the  pectoralis 
minor,  subclavius  and  serratus  magnus,  in  drawing  up  and  expanding  the 


368  THE   DISSECTOR. 

chest.  The  pectoralis  minor,  in  addition  to  this  action,  draws  upon  the 
coracoid  process,  and  assists  in  rotating  the  scapula  upon  the  chest.  The 
subclavius  draws  the  clavicle  downwards  and  forwards,  and  thereby  as- 
sists in  steadying  the  shoulder.  The  serratus  magnus  is  the  great  ex- 
ternal inspiratory  muscle,  raising  the  ribs  when  the  shoulders  are  fixed, 
and  thereby  increasing  the  cavity  of  the  chest.  Acting  upon  the  scapula, 
it  draws  the  shoulder  forwards,  as  we  see  to  be  the  case  in  diseased  lungs, 
where  the  chest  has  become  almost  fixed  from  apprehension  of  the  ex- 
panding action  of  the  respiratory  muscles.  The  trapezius  muscle  carries 
the  entire  shoulder  upwards  and  backwards,  and  is  assisted  in  this  action 
by  the  levator  anguli  scapulae,  rhomboideus  minor,  and  rhomboideus 
major.  Acting  in  the  opposite  direction,  they  flex  the  vertebral  column 
towards  the  shoulder.  The  lower  fibres  of  the  trapezius  unite  with  the 
latissimus  dorsi,  in  drawing  the  shoulder  and  arm  downwards  and  back- 
wards. When  the  arms  are  fixed,  as  by  crutches,  or  seizing  the  branch 
of  a  tree,  the  latissimi  dorsi  muscles  lift  the  entire  trunk  and  carry  it 
forwards. 

The  supra-spinatus,  infra-spinatus,  teres  minor,  and  subscapularis  are 
the  circumductor  muscles  of  the  arm ;  they  regulate  the  movements  of 
the  head  of  the  humerus  against  the  glenoid  cavity.  The  deltoid  is  the 
elevator  muscle  of  the  arm  in  a  direct  line,  and,  by  means  of  its  exten- 
sive origin,  can  carry  the  arm  forwards  or  backwards  so  as  to  range  with 
the  hand  a  considerable  segment  of  a  large  circle.  The  arm,  raised  by 
the  deltoid,  is  a  good  illustration  of  a  lever  of  the  third  power,  so  com- 
mon in  the  animal  machine,  by  which  velocity  is  gained  at  the  expense 
of  power.  In  this  lever  the  weight  (hand)  is  at  one  extremity,  the  ful- 
crum (the  glenoid  cavity)  at  the  opposite  end,  and  the  power  (the  inser- 
tion of  the  muscle)  between  the  two,  but  nearer  the  fulcrum  than  the 
weight. 

The  muscles  of  the  anterior  brachial  region  are  flexors ;  the  coraco- 
brachialis  flexing  the  humerus  on  the  scapula,  and  carrying  it  inwards. 
The  biceps  and  brachialis  anticus  flex  the  forearm  upon  the  arm.  The 
former  possesses  also  the  additional  action  of  supinating  the  forearm,  by 
means  of  the  obliquity  of  its  insertion  into  the  tuberosity  of  the  radius. 
The  triceps  is  an  extensor  of  the  forearm ;  hence  its  title,  triceps  extensor 
cubiti. 

BRACHIAL  ARTERY. — The  brachial  artery,  the  continuation  of 
the  axillary,  passes  down  the  inner  side  of  the  arm,  from  the  lower 
border  of  the  tendons  of  the  latissimus  dorsi  and  teres  major,  to  a 
little  below  the  bend  of  the  elbow,  where  it  divides  into  the  radial 
and  ulnar  arteries. 

In  its  course  downwards,  it  is  placed  at  first  to  the  inner  side 
of  the  humerus,  but  soon  gets  in  front  of  the  bone.  It  rests  suc- 
cessively on  the  triceps,  coraco-brachialis,  and  brachialis  anticus. 
To  its  outer  side  is  the  coraco-brachialis  and  biceps,  the  latter 
somewhat  overlapping  it ;  to  its  inner  side  is  the  internal  cutaneous 
and  ulnar  nerve.  In  front  it  has  the  basilic  vein,  the  deep  fascia, 
and  the  median  nerve ;  the  latter  lies  to  its  outer  side  above, 
crosses  it  at  its  middle,  and  lower  down  gets  to  its  inner  side. 
In  immediate  relation  with  the  artery,  and  lying  in  the  same 
sheath,  are  the  brachial  venae  comites. 


BBACHIAL  AETERY.  369 

Operations. — The  brachial  artery  may  be  tied  in  the  middle  or  upper 
part  of  the  arm,  or  at  the  bend  of  the  elbow.  In  the  former  situation  an 
incision  two  inches  and  a  half  in  length  is  made  along  the  inner  border  of 
the  coraco-brachialis  and  biceps.  This  should  divide  the  integument,  super- 
ficial and  deep  fascia.  The  basilic  vein,  which  lies  in  front  of  the  sheath 
of  the  vessels  in  the  middle  of  the  arm,  should  be  drawn  aside,  as  also 
should  the  median  nerve  which  crosses  the  artery  from  without  inwards 
at  the  middle  of  its  course.  The  sheath  must  then  be  carefully  opened, 
and  a  needle  passed  beneath  the  artery,  taking  care  to  avoid  the  two 
veins  (venae  comites)  by  which  it  is  accompanied.  The  only  difficulty 
the  student  will  experience  in  this  operation  is  the  finding  of  the  sheath, 
which  is  placed  beneath  the  edge  of  the  biceps ;  it  is  therefore  necessary 
to  pronate  the  arm  in  performing  the  operation.  At  the  bend  of  the 
arm,  an  incision  two  inches  in  length  should  be  made  along  the  inner 
border  of  the  tendon  of  the  biceps  to  the  outer  side  of  the  median  basilic 
vein ;  the  integument  and  superficial  fascia  should  be  divided ;  next  the 
deep  fascia,  strengthened  in  this  situation  by  the  aponeurotic  band  given 
off  from  the  tendon  of  the  biceps.  The  sheath  of  the  vessels  may  then 
be  opened,  and  the  artery  secured,  as  it  lies  between  its  two  veins.  The 
median  nerve  lies  nearly  an  inch  to  the  inner  side  of  the  artery  at  this 
point. 

The  branches  of  the  brachial  artery  are  the — 

Superior  profunda,  Anastomotica  magna, 

Inferior  profnnda,  Muscular  and  nutrient. 

The  superior  profunda  arises  opposite  the  lower  border  of  the 
tendon  of  the  latissimus  dorsi,  and  winds  around  the  humerus, 
between  the  triceps  and  the  bone,  to  the  space  between  the  bra- 
chialis  anticus  and  supinator  longus,  where  it  inosculates  with  the 
radial  recurrent  artery.  It  accompanies  the  inusculo-spiral  nerve. 
In  its  course  it  gives  off  the  posterior  articular  artery,  which 
descends  to  the  elbow-joint,  and  a  more  superficial  branch  which 
descends  by  the  side  of  the  external  intennuscular  septum,  and 
inosculates  with  the  interosseous  articular  artery.  The  inferior 
muscular  branches  of  the  superior  profunda  inosculate  with  the 
inferior  profunda,  anastomotica  magna,  and  ulnar  recurrent  arte- 
ries. 

The  inferior  profunda  arises  from  about  the  middle  of  the 
brachial  artery,  and  descends  to  the  space  between  the  inner  con- 
dyle  and  olecranon  in  company  with  the  ulnar  nerve,  where  it 
inosculates  with  the  posterior  ulnar  recurrent.  lu  its  course  it 
pierces  the  intermuscular  septum. 

The  anastomotica  magna  is  given  off  nearly  at  right  angles 
from  the  brachial,  at  about  two  inches  above  the  joint.  It  passes 
directly  inwards  upon  the  brachialis  anticus  muscle,  pierces  the 
intermuscular  septum,  and  winds  around  the  humerus  to  inoscu- 
late with  the  superior  profunda.  On  the  brachialis  anticus  it 
divides  into  two  branches,  which  inosculate  with  the  anterior  and 
posterior  ulnar  recurrent  arteries  and  with  the  inferior  profunda. 


370  THE   DISSECTOR. 

The  muscular  branches  are  distributed  to  the  muscles  in  the 
course  of  the  artery,  viz  :  to  the  coraco-brachialis,  biceps,  del- 
toid, brachialis  anticus,  and  triceps.  The  nutrient  branch  is  given 
off  at  about  the  middle  of  the  arm,  and  passes  into  the  medullary 
foramen  situated  near  the  insertion  of  the  coraco-brachialis  muscle. 

The  NERVES  of  the  upper  arm  may  now  be  followed  in  their 
course  as  far  as  the  elbow,  and  their  branches  examined ;  but 
they  cannot  be  completely  studied  until  after  the  dissection  of  the 
forearm. 

The  MUSCULO-CUTANEOUS  NERVE  (external  cutaneous,  perforans 
Casserii)  arises  from  the  brachial  plexus  in  common  with  the 
external  head  of  the  median  ;  pierces  the  coraco-brachialis  muscle, 
and  passes  between  the  biceps  and  brachialis  anticus  to  the  outer 
side  of  the  bend  of  the  elbow,  where  it  perforates  the  fascia,  and 
divides  into  two  branches,  which  are  distributed  to  the  integu- 
ment of  the  outer  side  of  the  forearm  as  far  as  the  hand.  In  the 
muscular  part  of  its  course  it  gives  branches  to  the  coraco-bra- 
chialis, biceps,  and  brachialis  anticus. 

The  MEDIAN  nerve  arises  by  two  heads  which  proceed  from  the 
outer  and  inner  cords  of  the  brachial  plexus,  and  embrace  the 
axillary  artery.  The  nerve  lies  at  first  to  the  outer  side  of  the 
brachial  artery,  but  crosses  it  in  the  middle,  sometimes  in  front 
and  sometimes  behind,  and  getting  to  its  inner  side  descends  to 
the  bend  of  the  elbow.  It  gives  off  no  branch  in  the  upper  arm. 

The  ULNAR  NERVE,  somewhat  smaller  than  the  median,  arises 
from  the  inner  cord  of  the  plexus  in  common  with  the  inner  head 
of  that  nerve  ;  and  descends  upon  the  inner  side  of  the  brachial 
artery  to  about  its  middle.  It  then  pierces  the  intermuscular 
septum,  and  passes  down  upon,  and  partly  embedded  in,  the  inner 
portion  of  the  triceps  to  the  groove  between  the  internal  condyle 
and  the  olecranon ;  having  in  company  the  inferior  profuuda 
artery.  It  gives  off  no  branch  in  the  upper  arm. 

The  INTERNAL  CUTANEOUS  NERVE  arises  with  the  ulnarfrom  the 
inner  cord  of  the  brachial  plexus.  It  lies  at  first  to  the  inner  side 
of  the  brachial  artery,  but  shortly  gets  in  front  of  it,  and  at  the 
middle  of  the  arm  pierces  the  fascia,  and  divides  into  its  two 
cutaneous  branches  (page  365).  Soon  after  its  origin  it  gives  off 
a  cutaneous  branch,  which  pierces  the  fascia  immediately  below 
the  axilla. 

The  LESSER  INTERNAL  CUTANEOUS  NERVE  (Wrisberg's)  arises, 
with  the  two  preceding,  from  the  inner  cord  of  the  plexus,  and, 
issuing  from  beneath  the  axillary  vein,  descends  the  inner  side  of 
the  arm  to  the  middle  of  its  posterior  aspect,  where  it  pierces  the 
deep  fascia  and  becomes  cutaneous.  In  the  axilla  it  communi- 
cates with  the  intercosto-humeral  nerve. 

The  CIRCUMFLEX  NERVE  proceeds  from  the  posterior  cord  of 


ANATOMY  OF  THE  FOREARM.  371 

the  brachial  plexus,  and  lies  behind  the  axillary ;  its  course  and 
branches  have  been  already  described  (page  358). 

The  MUSCULO-SPIRAL  NERVE,  the  largest  branch  of  the  brachial 
plexus,  arises  from  its  posterior  trunk  in  common  with  the  cir- 
cumflex, and,  descending  behind  the  axillary  and  brachial  artery, 
winds  around  the  humerus  between  the  triceps  and  the  bone,  and 
in  company  with  the  superior  profuuda  artery  to  the  space  between 
the  brachialis  anticus  and  supinator  longus,  and  thence  onwards 
to  the  bend  of  the  elbow,  where  it  divides  into  two  branches, 
radial  and  posterior  interosseous. 

The  branches  of  the  musculo-spiral  nerve  in  the  upper  arm  are 
muscular  and  cutaneous. 

The  muscular  branches  are  distributed  to  the  triceps,  anco- 
neus,  brachialis  anticus,  supinator  longus,  and  extensor  carpi 
radialis  longior. 

The  cutaneous  branches  are  three  in  number — internal,  and  two 
external.  The  internal  branch  arises  from  the  nerve  in  the  axilla, 
and  pierces  the  deep  fascia  in  the  upper  third  of  the  arm  on  its 
posterior  aspect  (page  366).  The  external  branches  pass  through 
the  substance  of  the  external  head  of  the  triceps,  and  pierce  the 
deep  fascia ;  one  (upper)  near  the  insertion  of  the  deltoid,  the 
other  or  lower  branch  at  about  the  middle  of  the  upper  arm. 

ANATOMY  OF  THE  FOREARM. 

An  incision  may  now  be  carried  along  the  front  of  the  forearm,  from 
the  elbow  to  the  wrist,  and  terminated  in  the  latter  situation  by  a  trans- 
verse incision.  The  integument  should  then  be  dissected  back  on  either 
side,  and  the  dissection  carried  completely  around  the  arm.  Further- 
more, the  integument  should  be  raised  in  the  same  manner  from  the  back 
of  the  hand  and  fingers,  leaving  the  palm  of  the  hand  for  subsequent 
dissection. 

In  the  superficial  fascia  of  J:he  front  of  the  forearm  will  be  found 
a  number  of  superficial  veins,  which  may  be  followed  downwards 
to  the  hand,  and  some  cutaneous  nerves. 

CUTANEOUS  VEINS. — The  radial  vein  commences  on  the  dorsnra 
of  the  hand,  in  the  radial  termination  of  a  venous  arch,  which 
receives  the  veins  of  the  fingers.  This  origin  is  increased  by  the 
junction  of  some  small  veins  from  the  thumb.  The  radial  vein 
ascends  the  dorsal  side  of  the  forearm  to  a  little  below  its  middle, 
then  lies  on  its  anterior  aspect  to  the  bend  of  the  elbow,  where 
it  receives  the  median  cephalic,  and  becomes  the  cephalic  vein. 

The  posterior  ulnar  vein  begins  in  the  ulnar  extremity  of  the 
venous  arch,  and,  after  receiving  a  large  vein — the  vena  salvatella 
— from  the  little  finger,  ascends  along  the  posterior  aspect  of  the 
forearm  to  the  bend  of  the  elbow,  where  it  turns  forward  and 
terminates  in  the  anterior  ulnar  vein. 


3t2  THE   DISSECTOR. 

The  anterior  ulnar  vein,  beginning  at  the  wrist,  ascends  along 
the  anterior  aspect  of  the  inner  side  of  the  forearm  to  the  bend  of 
the  elbow,  where  it  receives  the  median  basilic,  and  becomes  the 
basilic  vein. 

The  median  vein  begins  upon  the  front  of  the  wrist  by  the 
junction  of  branches  from  the  palm  of  the  hand,  and  passing 
upwards  along  the  front  of  the  forearm,  terminates  just  below  the 
bend  of  the  elbow  by  dividing  into  the  median  cephalic  and 
median  basilic. 

CUTANEOUS  NERVES. — The  superficial  nerves  situated  upon  the 
outer  side  of  the  front  of  the  forearm  are  the  musculo-cutaneous, 
the  external  cutaneous  of  the  musculo-spiral,  and,  a  little  above 
the  wrist,  the  radial  nerve  in  its  course  to  the  back. of  the  hand. 
Those  on  the  inner  side  of  the  forearm  are  the  internal  cutaneous, 
and,  lower  down,  a  cutaneous  branch  of  the  ulnar.  On  the  middle, 
a  little  above  the  wrist,  is  the  palmar  cutaneous  branch  of  the 
median ;  and  on  the  back  of  the  hand  is  the  radial  nerve  and  a 
branch  of  the  ulnar. 

The  musculo-cutaneous  nerve,  after  becoming  superficial  at  the 
elbow,  divides  into  an  anterior  and  a  posterior  branch.  The 
anterior  branch  passes  along  the  outer  border  of  the  forearm,  and, 
at  its  lower  part,  overlies  the  radial  artery.  At  the  wrist  it  gives 
several  filaments  to  the  ball  of  the  thumb,  and  pierces  the  deep 
fascia  to  accompany  the  radial  artery  to  the  back  of  the  wrist. 
The  posterior  branch,  smaller  than  the  anterior,  follows  the  outer 
border  of  the  forearm  on  its  posterior  aspect,  and  is  distributed 
to  the  integument  as  far  as  the  wrist;  it  communicates  with  the 
radial  nerve  and  with  the  external  cutaneous  branch  of  the  mus- 
culo-spiral. 

The  cutaneous  branch  of  the  musculo-spiral  nerve  passes  down 
the  outer  side  of  the  forearm,  and,  at  about  the  middle,  reaches 
its  posterior  aspect,  and  is  continued  to  the  wrist ;  it  communi- 
cates with  the  posterior  branch  of  the  musculo-cutaneous  nerve. 

The  internal  cutaneous  nerve  reaches  the  forearm  by  two 
branches  ;  the  anterior  branch  is  that  which  passes  in  front  of  the 
median  basilic  vein,  and  descends  along  the  forearm  to  the  wrist. 
The  posterior  branch  enters  the  forearm  behind  the  internal  con- 
dyle  of  the  humerus,  and  passes  down  the  posterior  aspect  of  the 
ulnar  border  of  the  forearm  to  its  lower  third. 

The  radial  nerve  pierces  the  deep  fascia  about  two  inches 
above  the  wrist  on  the  posterior  aspect  of  the  forearm,  and 
divides  into  two  branches,  which  are  distributed  to  the  integu- 
ment of  the  radial  half  of  the  hand.  The  external  branch  com- 
municates with  the  cutaneous  branch  of  the  musculo-cutaneous 
nerve,  and  is  distributed  to  the  radial  border  of  the  thumb.  The 
internal  branch  divides  into  filaments,  which  are  distributed  to 


DEEP  FASCIA — MUSCLES.  373 

the  ulnar  border  of  the  thumb,  to  the  index  and  middle  fingers, 
arid  the  radial  border  of  the  ring  finger.  This  branch  commu- 
nicates with  the  musculo-cutaneous  nerve,  and  with  the  ulnar. 
On  the  fingers,  the  digital  branches  communicate  with  those  of 
the  median  nerve. 

The  dorsal  branch  of  the  ulnar  nerve  pierces  the  deep  fascia 
on  the  wrist,  and  divides  into  two  branches,  one  of  which  forms 
an  arch  on  the  back  of  the  hand  by  communicating  with  the  ra- 
dial nerve,  while  the  others  are  distributed  to  the  little  finger  and 
half  the  ring  finger. 

The  DEEP  FASCIA  of  the  forearm  is  dense  and  thick,  particu- 
larly on  its  posterior  aspect.  It  is  continuous  above  with  the 
corresponding  fascia  of  the  upper  arm  ;  below,  it  is  connected 
with  the  anterior  annular  ligament  in  front,  and  behind  forms 
the  posterior  annular  ligament,  and  is  prolonged  onwards  to  the 
back  of  the  hand  and  fingers.  At  the  elbow  it  receives  an  aug- 
mentation of  fibres  from  the  tendon  of  the  biceps,  from  the  bra- 
chialis  anticus,  and  muscles  arising  from  the  internal  condyle, 
and  from  the  triceps  behind.  It  surrounds  all  the  muscles  of  the 
forearm,  forming  septa,  from  which  part  of  the  muscles  arise  ; 
and  constitutes  an  aponeurosis  of  separation  between  the  super- 
ficial and  deep  muscles.  Posteriorly  it  is  attached  to  the  ulna  ; 
arid  at  its  lower  part  in  front  gives  passage  to  the  tendon  of  the 
palmaris  longus  muscle. 

When  the  deep  fascia  has  been  examined,  an  incision  should  be  made 
along  the  front  of  the  forearm  from  the  elbow  to  the  wrist,  and  crossed 
in  the  latter  situation  by  a  transverse  section.  Before  this  is  done,  it  is 
proper  to  note  two  small  nerves,  which  should  be  spared  in  the  removal 
of  the  fascia.  One  of  these  is  the  palmar  cutaneous  branch  of  the  me- 
dian ;  it  pierces  the  fascia  just  above  the  wrist,  and  crosses  the  middle 
of  the  annular  ligament  to  reach  the  hand.  The  other  is  a  cutaneous 
branch  of  the  ulnar  nerve,  which  pierces  the  fascia  at  about  the  middle 
of  the  forearm,  and  passes  down  in  front  of  the  ulnar  artery  to  the  palm 
of  the  hand.  The  deep  fascia  is  to  be  raised  from  the  muscles  and  turned 
to  either  side  ;  in  doing  which  the  septa  between  the  muscles  should  be 
observed.  The  attachment  of  the  fibres  of  the  muscles  to  the  fascia  at 
their  upper  part  will  render  the  dissection  troublesome,  and  will  spoil 
the  appearance  of  the  muscles. 

The  MUSCLES  of  the  anterior  aspect  of  the  forearm  consist  of 
a  superficial  and  a  deep  group,  and  are  eight  in  number,  five  in 
the  superficial  layer,  and  three  in  the  deep ;  they  are  all  flexors 
and  pronators.  The  superficial  group  is  as  follows : — 

Pronator  radii  teres, 

Flexor  carpi  radialis, 

Palmaris  longus, 

Flexor  carpi  ulnaris, 

Flexor  sublimis  digitorum. 
32 


374 


THE   DISSECTOR. 


Fig.  112. 


\V 


The  PRONATOR  RADII  TERES  arises  by  two  heads,  one  from  the 
inner  condyle  of  the  huinerus,  deep  fascia,  and  interinuscular 
septum;  the  other  from  the  coronoid  process  of  the  ulna;  the 
median  nerve  passing  between  them.  Its  tendon  is  flat,  and  is 
inserted  into  the  middle  third  of  the  oblique  ridge  of  the  radius. 
The  two  heads  of  this  muscle  are  best  seen  by  cutting  away  that 
which  arises  from  the  inner  condyle,  and  turning  it  aside.  The 
second  head  will  then  be  seen  with  the  median  nerve  lying  across  it. 
The  pronator  radii  teres  forms  the  inner 
border  of  a  triangular  space,  bounded  ex- 
ternally by  the  supinator  longus,  and  above 
by  the  brachialis  anticus,  which  contains 
the  termination  of  the  brachial  artery, 
where  it  bifurcates  into  the  radial  and  ulnar 
artery,  the  median  nerve,  the  tendon  of  the 
biceps,  and  the  musculo-spiral  nerve.  The 
latter  lies  under  cover  of  the  supinator 
longus. 

The  FLEXOR  CARPI  RADIALIS  arises  from 
the  inner  condyle,  deep  fascia,  and  inter- 
muscular  septa.  Its  tendon  passes  through 
a  groove  in  the  trapezium  bone,  to  be  in- 
serted into  the  base  of  the  metacarpal  bone 
of  the  index  finger. 

The  PALMARIS  LONGUS  muscle  arises  from 
the  inner  condyle,  deep  fascia,  and  inter- 
muscular  septa.  Its  tendon  pierces  the 
deep  fascia  and  crosses  the  annular  liga- 
ment, to  be  inserted  into  the  palmar 
fascia. 

The  FLEXOR  CARPI  ULNARis  arises  by  two 
heads,  one  from  the  inner  condyle  and  in- 
termuscular septa,  the  other  from  the  ole- 
cranon,  and  by  means  of  a  strong  aponeu- 
rosis  from  two-thirds  of  the  inner  border 
of  the  ulna.  The  ulnar  nerve  passes  be- 
tween its  two  heads.  Its  tendon  is  inserted 

SUPERFICIAL  LAYER  OF  MUSCLES  OF  THE  FOREARM. — 1.  The  lower  part 
of  the  biceps,  with  its  tendon.  2.  A  part  of  the  brachialis  anticus,  seen  beneath 
the  biceps.  3.  A  part  of  the  triceps.  4.  The  pronator  radii  teres.  5.  The 
flexor  carpi  radialis.  6.  The  palmaris  longus.  7.  One  of  the  fasciculi  of  the 
flexor  sublimus  digitorum  ;  the  rest  of  the  muscle  is  seen  beneath  the  tendons  of 
the  palmaris  longus  and  flexor  carpi  radialis.  8.  The  flexor  carpi  ulnaris.  9. 
The  palmar  fascia.  10.  The  palmaris  brevis  muscle.  11.  The  abductor  pollicis 
muscle.  12.  One  portion  of  the  flexor  brevis  pollicis ;  the  leading  line  crosses 
a  part  of  the  adductor  pollicis.  13.  The  supinator  longus  muscle.  14.  The 
extensor  ossis  metacarpi,  and  extensor  primi  internodii  pollicis,  curving  around 
the  lower  border  of  the  forearm. 


FLEXOR  8UBLIMIS — FLEXOR  PROFUNDUS, 


375 


Fig.  113. 


into  the  pisiform  bone,  and  base  of  the  metacarpal  bone  of  the 
little  finger. 

The  flexor  carpi  radialis  and  palmaris  longus  should  now  be  divided 
near  their  origin,  and  the  flexor  carpi  ulnaris  drawn  aside  in  order 
to  bring  into  view  the  flexor  sublimis  digitorum  which  lies  beneath 
them. 

The  FLEXOR  SUBLIMIS  DIGITORUM  (perforatus),  arises  from  the 
inner  condyle,  intermuscular  septa,  internal  lateral  ligament,  co- 
ronoid  process  of  the  ulna,  and  oblique  line  of  the  radius.  The 
median  nerve  and  ulnar  artery  pass  between  its  origins.  It 
divides  into  four  tendons,  which  pass  be- 
neath the  annular  ligament,  and  are  in- 
serted into  the  base  of  the  second  phalanges 
of  the  fingers,  splitting  at  their  termina- 
tions to  give  passage  to  the  tendons  of 
the  deep  flexors  ;  thence  its  designation 
perforatus. 

The  deep  layer  of  muscles  is  brought 
into  view  by  dividing  the  flexor  sublimis 
through  its  tendons,  and  drawing  the 
muscle  upwards  and  outwards,  and  at  the 
same  time  drawing  aside  the  pronator 
radii  teres.  These  muscles  should  be  as 
little  disturbed  as  possible,  in  order  to 
avoid  dislocating  the  bloodvessels  and 
nerves,  and  when  the  latter  are  studied 
they  should  be  replaced.  The  deep  mus- 
cles of  the  forearm  are  the — 

Flexor  profundus  digitorum, 

Flexor  longus  pollicis, 

Pronator  quadratus. 

The      FLEXOR      PROFUNDUS     DIGITORUM 

(perforans),  arises  from  the  inner  border 
and  anterior  surface  of  the  ulna  for  three- 
fourths  of  its  extent,  from  the  inner  side 
of  the  olecranon,  and  one-half  the  inter- 
osseous  membrane.  The  muscle  termi- 
nates in  four  tendons,  which  pass  beneath 
the  annular  ligament,  and  on  the  fingers, 
between  the  two  slips  of  the  flexor  subli- 

THE  DEEP  LAYER  OF  MUSCLES  OF  THE  FOREARM. — 1.  The  internal  lateral 
ligament  of  the  elbow-joint.  2.  The  anterior  ligament.  3.  The  orbicular  liga- 
ment of  the  head  of  the  radius.  4.  The  flexor  profundus  digitorum  muscle. 
5.  The  flexor  longus  pollicis.  6.  The  pronator  quadratus.  7.  The  adductor 
pollicis  muscle.  8.  The  dorsal  interosseous  muscle  of  the  middle  finger,  and 
palmar  interosseous  of  the  ring-finger.  9.  The  dorsal  interosseous  muscle  of 
the  ring-finger,  and  palmar  interosseous  of  the  little  finger. 


376  THE  DISSECTOR. 

mis  (hence  its  designation  perforans),  to  be  inserted  into  the 
base  of  the  last  phalanges.  The  tendon  for  the  index  finger  is 
distinct  from  the  rest,  the  other  three  being  more  or  less  con- 
nected by  cellular  tissue  and  tendinoos  slips. 

The  FLEXOR  LONGUS  POLLicis  arises  from  the  anterior  surface  of 
the  radius  for  two-thirds  of  its  extent,  and  from  one-half  of  the 
interosseous  membrane.  Its  tendon  passes  beneath  the  annular 
ligament,  to  be  inserted  into  the  base  of  the  last  phalanx  of  the 
thumb. 

The  PRONATOR  QUADRATUS  lies  across  the  radius  and  ulna  for 
the  lower  fourth  of  their  extent ;  it  arises  from  the  anterior  and 
inner  side  of  the  ulna,  and  is  inserted  into  the  front  of  the  radius. 
The  muscle  is  broader  at  its  origin  than  at  its  insertion. 

Actions. — The  pronator  radii  teres  and  pronator  quadratus  muscles 
rotate  the  radius  upon  the  ulna,  and  render  the  hand  prone.  The  re- 
maining muscles  are  flexors  :  two  flexors  of  the  wrist,  flexor  carpi  radialis 
and  ulnaris ;  two  of  the  fingers,  flexor  sublimis  and  profundus,  the  former 
flexing  the  second  phalanges,  the  latter  the  last ;  one  flexor  of  the  last 
phalanx  of  the  thumb,  flexor  longus  pollicis.  The  palmaris  longus  is 
primarily  a  tensor  of  the  palmar  fascia,  and  secondarily  a  flexor  of  the 
wrist  and  forearm. 

The  VESSELS  of  the  anterior  region  of  the  forearm  are  the  ra- 
dial and  ulnar,  with  their  veins  and  branches. 

The  RADIAL  ARTERY,  one  of  the  divisions  of  the  brachial, 
passes  down  the  radial  side  of  the  forearm  from  the  bend  of  the 
elbow  to  the  wrist;  it  then  turns  backwards  around  the  base  of 
the  thumb,  and  passing  through  the  first  interosseous  space 
between  the  two  heads  of  the  first  dorsal  interosseous  muscle, 
enters  the  palm  of  the  hand  and  becomes  the  deep  palmar  arch. 

In  the  upper  half  of  its  course,  the  radial  artery  is  placed  be- 
tween the  supinator  longus,  by  which  it  is  slightly  overlapped, 
and  the  pronator  radii  teres ;  in  the  lower  half,  between  the  ten- 
dons of  the  supinator  longus  and  flexor  carpi  radialis.  It  rests 
in  succession  on  the  supinator  brevis,  pronator  radii  teres,  radial 
origin  of  the  flexor  sublimis,  flexor  longus  pollicis,  and  pronator 
quadratus ;  and  is  covered  in  by  the  integument  and  fasciae.  At 
the  wrist  it  is  in  contact  with  the  external  lateral  ligament,  and 
beneath  the  extensor  tendons  of  the  thumb.  It  is  accompanied 
by  venae  comites,  and  is  in  close  relation  by  its  middle  third  with 
the  radial  nerve,  which  lies  to  its  outer  side. 

Operations. — The  radial  artery  may  be  tied  in  any  part  of  its  course, 
either  above,  where  it  is  placed  between  the  supinator  longus  and  pro- 
nator teres,  or  below,  between  the  tendons  of  the  supinator  longus  and 
flexor  carpi  radialis.  In  either  case  the  border  of  the  supinator  longus 
is  the  guide  for  the  incision  (two  inches  long);  and  the  same  parts  are 
to  be  divided  in  both,  viz :  the  integument,  superficial,  and  deep  fascia. 
The  operation,  at  the  upper  part  of  the  arm,  will  require  the  longer  inci- 


ARTERIES  OF   THE   FOREARM.  37T 

sion  on  account  of  the  greater  depth  of  the  vessel,  though  the  difference 
in  that  particular  is  very  trifling.  In  the  middle  third  of  its  course  the 
radial  artery  is  accompanied  by  the  radial  nerve. 

The  radial  artery  may  likewise  be  tied  where  it  is  winding  around  the 
root  of  the  thumb,  to  enter  the  palm  of  the  hand.  In  this  operation  the 
incision  should  be  made  along  the  middle  of  the  space  between  the  ten- 
dons of  the  extensor  primi  and  secundi  internodii.  In  dividing  the  su- 
perficial fascia,  one  or  two  branches  of  veins  may  be  wounded,  and  a 
branch  of  the  dorsal  division  of  the  radial  nerve  which  crosses  the  space. 
The  artery  is  placed  deeply  upon  the  trapezium  bone,  and  is  accompanied 
by  its  two  venae  comites. 

The  branches  of  the  radial  artery  in  the  forearm  and  at  the 
wrist  are  the — 

Radial  recurrent,  Posterior  carpal, 

Muscular,  Metacarpal, 

Superficialis  volae,  Borsales  pollicis, 

Anterior  carpal,  Dorsalis  indicis. 

The  radial  recurrent  branch,  given  off  just  below  the  elbow, 
passes  outwards  to  the  supinator  longus  muscle,  and  gives  off 
several  branches  for  the  supply  of  the  muscles  arising  from  the 
external  condyle ;  it  then  ascends  in  the  space  between  the  supi- 
nator longus  and  brachialis  auticus,  and  inosculates  with  the 
superior  profunda. 

The  muscular  branches  are  distributed  to  the  muscles  of  the 
radial  border  of  the  forearm. 

The  superficialis  voice  arises  from  the  radial  at  the  wrist  and 
crosses  the  ball  of  the  thumb,  generally  piercing  the  abductor 
pollicis  muscle,  to  inosculate  with  the  ulnar  artery  and  complete 
the  superficial  palmar  arch.  This  artery  varies  much  in  size, 
being  sometimes  a  mere  twig  and  sometimes  a  bifurcation  of  the 
radial. 

The  anterior  carpal  branch  passes  inwards  along  the  lower 
border  of  the  pronator  quadratus,  and  forms  an  arch  by  inoscu- 
lating with  the  anterior  carpal  branch  of  the  ulnar  artery.  From 
this  arch  twigs  are  given  off  to  supply  the  wrist-joint. 

The  posterior  carpal  branch  proceeding  from  the  radial  while 
in  relation  with  the  wrist,  crosses  the  carpus  transversely,  and 
inosculates  with  the  posterior  carpal  branch  of  the  ulnar  artery. 
From  this  arch  are  given  off  the  dorsal  interosseous  branches  of 
the  third  and  fourth  metacarpal  spaces.  The  latter  are  joined 
over  the  heads  of  the  interossei  muscles  by  the  perforating  branches 
of  the  deep  palmar  arch. 

The  metacarpal  or  first  dorsal  interosseous  branch  passes  for- 
wards to  the  metacarpal  space  between  ths  index  and  middle 
finger.  At  the  cleft  of  the  fingers  it  inosculates  with  the  palmar 
digital  artery,  and  gives  off  dorsal  collateral  branches,  It  is 

32* 


378 


THE  DISSECTOR. 


Fig.  114. 


joined  over  the  heads  of  the  interosseous  muscle  by  the  perforating 
branch  from  the  deep  palmar  arch. 

The  dorsales  pollicis  are  two  small 
branches  which  run  along  the  sides  of 
the  dorsal  aspect  of  the  thumb. 

The  dorsalisindicis  is  a  small  branch 
which  runs  along  the  radial  border  of 
the  metacarpal  bone  and  phalanges  of 
the  index  finger. 

The  ULNAR  ARTERY,  the  other  and 
larger  division  of  the  brachial  artery, 
crosses  the  forearm  obliquely  to  the 
commencement  of  its  middle  third ;  it 
then  runs  down  its  ulnar  side  to  the 
wrist,  crosses  the  annular  ligament, 
and  forms  the  superficial  palmar  arch, 
which  terminates  by  inosculating  with 
the  superficialis  volae. 

In  the  upper  or  oblique  portion  of 
its  course,  the  ulnar  artery  lies  upon 
the  brachialis  anticus  and  flexor  pro- 
fundus  digitorum,  and  is  covered  in 
by  the  superficial  layer  of  muscles  of 
the  forearm  and  by  the  median  nerve. 
In  the  second  part  of  its  course,  it  is 
placed  upon  the  flexor  profundus  and 
pronator  quadratus,  lying  between  the 
flexor  carpi  ulnaris  and  flexor  subli- 
mis  digitorum.  While  crossing  the 
annular  ligament  it  is  protected  from 
injury  by  a  strong  tendinous  arch, 
thrown  over  it  from  the  pisiform  bone. 
It  is  accompanied  in  its  course  by 

THE  ARTERIES  OF  THE  FOREARM. — 1.  The  lower  part  of  the  biceps  muscle. 
2.  The  inner  condyle  of  the  humerus  with  the  humeral  origin  of  the  pronator 
radii  teres  and  flexor  carpii  radialis  divided  across.  3.  The  deep  portion  of 
the  pronator  radii  teres.  4.  The  supinator  longus  muscle.  5.  The  flexor  longus 
pollicis.  6.  The  pronator  quadratus.  7.  The  flexor  profundus  digitorum.  8. 
The  flexor  carpi  ulnaris.  9.  The  annular  ligament  with  the  tendons  passing 
beneath  it  into  the  palm  of  the  hand  ;  the  figure  is  placed  on  the  tendon  of  the 
palmaris  longus  muscle  divided  close  to  its  insertion.  10.  The  brachial  artery. 
11.  The  anastomotica  magna  inosculating  superiorly  with  the  inferior  profunda, 
and  inferiorly  with  the  anterior  ulnar  recurrent.  12.  The  radial  artery.  13. 
The  radial  recurrent  artery  inosculating  with  the  termination  of  the  superior 
profunda.  14.  The  suj>erficialis  volee.  15.  The  ulnar  artery.  16.  Its  superfi- 
cial palmar  arch  giving  off  digital  branches  to  three  fingers  and  a  half.  17. 
The  magna  pollicis  and  radialis  indicis  arteries.  18.  The  posterior  ulnar  recur- 
rent. 19.  The  anterior  interosseous  artery.  20.  The  posterior  interosseous,  as 
it  is  passing  through  the  interoseeous  membrane. 


ARTERIES   OF   THE   FOREARM.  379 

the  venae  comites,  and  is  in  relation  with  the  nlnar  nerve  for 
the  lower  two-thirds  of  its  extent ;  the  nerve  lying  to  its  ulnar 
side.  / 

Operations. — The  ulnar  artery  is  usually  tied  in  three  situations  :  1st. 
At  the  commencement  of  the  middle  third  of  the  forearm,  where  it 
emerges  from  beneath  the  flexor  sublimis.  2d.  In  the  lower  third.  3d. 
As  it  crosses  the  annular  ligament.  In  the  first  two  operations  the  border 
of  the  flexor  carpi  ulnaris  muscle  and  tendon  is  the  guide  for  the  incision, 
in  the  latter  the  pisiform  bone.  The  high  operation  is  the  most  difficult, 
on  account  of  the  depth  of  the  artery  and  the  danger  of  separating  the 
wrong  muscles.  The  lower  operations  are  simple  and  easy,  the  artery 
lying  quite  superficially.  The  ulnar  nerve  lies  immediately  to  the  ulnar 
side  of  the  artery  from  the  commencement  of  the  middle  third  to  the 
wrist,  and  therefore  is  not  endangered  in  the  upper  operation.  The  venae 
comites  are  one  at  each  side.  The  structures  to  be  cut  through  are  the 
integument,  superficial  fascia,  deep  fascia,  the  sheath  of  the  vessels,  and,  at 
the  wrist,  the  palmaris  brevis  muscle  and  tendinous  band.  The  length 
of  incision  for  the  upper  operation  is  three  inches,  and  for  the  lower  two. 

In  wounds  of  arteries,  wherever  they  occur,  both  extremities  of  the 
vessel  are  to  be  tied ;  and  this  is  the  rule  of  practice  for  wounds  in  the 
palm  of  the  hand. 

The  branches  of  the  nlnar  artery  in  the  forearm  are  the — 
Anterior  ulnar  recurrent,  Anterior  carpal, 

Posterior  ulnar  recurrent,  Posterior  carpal, 

Jnterosseous,  Metacarpal. 

Muscular, 

The  anterior  ulnar  recurrent  arises  immediately  below  the 
elbow,  and  ascending  between  the  pronator  radii  teres  and  bra- 
chialis  anticus  gives  branches  to  the  muscles  and  inosculates  with 
the  inferior  profunda  and  anastomotica  magna.  This  artery  fre- 
quently arises  from  a  common  trunk  with  the  following  : — 

The  posterior  ulnar  recurrent,  larger  than  the  preceding,  passes 
beneath  the  flexor  sublimis  digitorum  muscle  to  the  notch  between 
the  inner  condyle  and  the  olecranon,  where  it  is  in  relation  with 
the  ulnar  nerve,  and  inosculates  with  the  inferior  profunda  and 
anastomotica  magna. 

The  interosseous  artery  is  a  short  trunk,  which  arises  opposite 
the  tuberosity  of  the  biceps,  and  passes  backwards  to  the  interos- 
seous membrane,  where  it  divides  into  the  anterior  and  posterior 
interosseous. 

The  anterior  interosseous  artery  passes  down  the  front  of  the 
interosseous  membrane,  between  the  flexor  profundus  digitorum 
and  flexor  longus  pollicis,  and  behind  the  pronator  quadratus ;  it 
then  passes  through  an  opening  in  the  interosseous  membrane  to 
the  back  of  the  wrist,  where  it  inosculates  with  the  posterior 
carpal  branches  of  the  radial  and  ulnar.  The  anterior  iuteros- 
seous  artery  gives  off  several  muscular  branches;  nutrient  branches 
to  the  radius  and  ulna;  a  companion  branch  to  the  median  nerve  ; 


380  THE   DISSECTOR. 

and  at  the  upper  border  of  the  pronator  quadratus,  a  small 
branch,  which  descends  behind  that  muscle  to  inosculate  with  the 
anterior  carpal  arteries.  ^ 

The  posterior  interosseous  artery  passes  backwards  through  an 
opening  between  the  upper  part  of  the  interosseous  membrane 
and  the  oblique  ligament,  and  descends  between  the  superficial 
and  deep  layer  of  muscles  of  the  back  of  the  forearm  to  the  wrist, 
where  it  inosculates  with  the  posterior  carpal  arteries,  and  with 
the  termination  of  the  anterior  interosseous.  The  posterior  inter- 
osseous artery  gives  off  at  its  upper  part  a  recurrent  branch,  which 
ascends  between  the  supinator  brevis  and  extensor  carpi  ulnaris, 
and  enters  the  anconeus,  where  it  inosculates  with  a  branch  of 
the  superior  profunda. 

The  muscular  branches  of  the  ulnar  artery  are  distributed  to 
the  muscles  of  the  ulnar  border  of  the  forearm. 

The  anterior  carpal  branch  crosses  in  front  of  the  wrist-joint, 
and  inosculates  with  the  anterior  carpal  branch  of  the  radial 
artery,  forming  an  anterior  carpal  arch. 

The  posterior  carpal  branch,  taking  a  similar  course  across  the 
back  of  the  wrist,  forms,  with  a  similar  inosculation,  a  posterior 
carpal  arch. 

The  metacarpal  branch,  often  a  branch  of  the  preceding,  passes 
along  the  inner  border  of  the  metacarpal  bone  of  the  little  finger, 
and  forms  the  dorsal  collateral  branch  of  that  finger. 

The  NERVES  of  the  forearm  are  the  radial,  ulnar,  and  median, 
which  belong  to  its  anterior  aspect ;  and  the  interosseous,  the 
nerve  of  its  posterior  region. 

The  RADIAL  NERVE,  one  of  the  terminal  branches  of  the  mus- 
culo-spiral  (page  371),  passes  downwards  along  the  outer  side  of 
the  radial  artery,  and  overlapped  by  the  supinator  longus  to  the 
lower  third  of  the  forearm,  where  it  turns  beneath  the  tendon  of 
that  muscle,  and  piercing  the  deep  fascia  is  distributed  to  the 
back  of  the  hand,  the  thumb,  and  two  fingers  and  a  half  (page 
372). 

The  MEDIAN  NERVE  (page  370),  lying  in  the  hollow  of  the 
bend  of  the  elbow,  passes  between  the  two  heads  of  the  pronator 
radii  teres.  It  next  gets  beneath  the  flexor  sublimis  digitorum, 
and  descends  the  middle  of  the  forearm,  lying  between  that  muscle 
and  the  flexor  profundus  to  its  lower  fourth.  There  it  becomes 
superficial,  and  running  along  the  outer  border  of  the  tendons  of 
the  flexor  sublimis,  passes  beneath  the  annular  ligament,  and 
enters  the  palm  of  the  hand. 

The  branches  of  the  median  nerve  in  the  forearm  are,  muscular, 
anterior  interosseous,  and  superficial  palmar. 

The  muscular  branches  are  distributed  to  all  the  muscles  of 


POSTERIOE  REGION  OP  THE  FOREARM.  381 

the  superficial  layer,  except  the  flexor  carpi  ulnaris,  and  to  one 
of  the  deep  layer,  the  flexor  profundus  digitorum,  its  radial  half. 

Tke  anterior  interosseous  nerve,  of  large  size,  accompanies  the 
anterior  interosseous  artery,  and  supplies  the  deep  layer  of 
muscles  of  the  front  of  the  forearm. 

The  superficial  palmar  branch  leaves  the  median  nerve  at  the 
lower  part  of  the  forearm,  and  piercing  the  deep  fascia,  crosses 
the  annular  ligament,  and  is  distributed  to  the  integument  of  the 
palm  of  the  hand. 

The  TJLNAR  NERVE  (page  3 tO),  entering  the  forearm  in  the 
groove  behind  the  internal  condyle  between  the  two  heads  of  the 
flexor  carpi  ulnaris,  comes  into  relation  with  the  ulnar  artery  at 
the  commencement  of  its  middle  third.  It  then  descends  along 
the  inner  side  of  the  artery  to  the  wrist,  crosses  with  it  the  annu- 
lar ligament,  and  divides  into  two  palmar  branches. 

The  branches  of  the  ulnar  nerve  in  the  forearm  are,  articular, 
muscular,  cutaneous,  and  dorsal  cutaneous. 

The  articular  branches  are  given  to  the  elbow-joint,  while  the 
nerve  lies  in  the  groove  between  the  internal  condyle  and  the 
olecranon. 

The  muscular  branches  are  distributed  to  the  flexor  carpi 
ulnaris,  and  inner  half  of  the  flexor  profundus  digitorum. 

The  cutaneous  branch  proceeds  from  about  the  middle  of  the 
nerve,  and  descends  upon  the  ulnar  artery  to  the  hand,  giving 
twigs  to  the  integument  in  its  course.  One  branch  from  its  upper 
part,  sometimes  a  separate  offset  from  the  nerve,  and  sometimes 
absent,  pierces  the  fascia,  and  communicates  with  the  internal 
cutaneous  nerve. 

The  dorsal  cutaneous  branch  passes  backwards,  beneath  the 
tendon  of  the  flexor  carpi  ulnaris,  at  the  lower  third  of  the  fore- 
arm, and  piercing  the  deep  fascia,  supplies  the  ulnar  side  of  the 
back  of  the  hand,  and  one  finger  and  a  half  (page  373). 

The  POSTERIOR  INTEROSSEOUS,  the  other  division  of  the  musculo- 
spiral  nerve  a^  the  bend  of  the  elbow,  pierces  the  supinator  brevis 
muscle,  and  is  distributed  to  the  back  of  the  forearm.  Its  further 
examination  must  therefore  be  reserved  until  the  posterior  aspect 
of  the  forearm  is  dissected. 

Posterior  Region  of  the  Forearm. 

The  deep  fascia  may  now  be  dissected  from  the  posterior  aspect  of  the 
forearm  in  a  manner  similar  to  that  practised  on  the  anterior  aspect ; 
the  longitudinal  incision  should  be  bounded  by  a  transrerse  incision 
made  along  the  upper  border  of  the  posterior  annular  ligament,  and  the 
fascia  turned  to  either  side.  The  posterior  annular  ligament  is  attached 
externally  to  the  radius,  and  internally  to  the  pisiform  bone,  and  forms 
separate  sheaths  for  the  passage  of  the  tendons  of  muscles  to  the  hand. 


382 


THE  DISSECTOR. 


The  MUSCLES  of  the  posterior  region  of  the  forearm  are  a  su- 
perficial and  a  deep  group  ;  the  superficial 
Fig.  115.  group  or  layer  consists  of  seven  muscles, 

namely : — 

Supinator  longus, 

Extensor  carpi  radialis  longior, 

carpi  radialis  brevior, 

communis  digitorum, 

minimi  digiti, 

• carpi  ulnaris, 

Anconeus. 

The  SUPINATOR  LONGUS  muscle  is  placed 
along  the  radial  border  of  the  forearm. 
It  arises  from  the  external  condyloid  ridge 
of  the  humerus,  nearly  as  high  as  the  in- 
sertion of  the  deltoid,  and  from  the  inter- 
muscular  septum  ;  and  is  inserted  into  the 
base  of  the  styloid  process  of  the  radius. 

This  muscle  must  be  divided  through 
the  middle,  and  the  two  ends  turned  to 
either  side  to  expose  the  next  muscle. 

The  EXTENSOR  CARPI  RADIALIS  LONGIOR 

arises  from  the  external  condyloid  ridge 
below  the  preceding,  and  from  the  inter- 
muscular  septum.  Its  tendon  passes 
through  a  groove  in  the  radius,  imme- 
diately behind  the  styloid  process,  to  be 
inserted  into  the  base  of  the  metacarpal 
bone  of  the  index  finger. 

The  EXTENSOR  CARPI  RADIALIS  BREVIOR 

is  seen  by  drawing  aside  the  former  mus- 

THE  SUPERFICIAL  LAYER  OF  MUSCLES  OF  THE  POSTERIOR  ASPECT  OF  THE 
FOREARM. — 1.  The  lower  part  of  the  biceps.  2.  Part  of  the  brachialis  anticus. 
3.  The  lower  part  of  the  triceps,  inserted  into  the  olecranon.  **t.  The  supinator 
longus.  5.  The  extensor  carpi  radialis  longior.  6.  The  extensor  carpi  radialis 
brevior.  7.  The  tendons  of  insertion  of  these  two  muscles.  8.  The  extensor 
communis  digitorum.  9.  The  extensor  minimi  digiti.  10.  The  extensor  carpi 
ulnaris.  11.  The  anconeus.  12.  Part  of  the  flexor  carpi  ulnaris.  13.  The 
extensor  ossis  metacarpi  and  extensor  primi  internodii  muscle,  lying  together. 
14.  The  extensor  secundi  internodii ;  its  tendon  is  seen  crossing  the  two  tendons 
of  the  extensor  carpi  radialis  longior  and  brevior.  15.  The  posterior  annular 
ligament.  The  tendons  of  the  common  extensor  are  seen  upon  the  back  of  the 
hand,  and  their  mode  of  distribution  on  the  dorsum  of  the  fingers. 

cle.  It  arises  from  the  external  condyle  of  the  humerus  and 
intermuscular  septa,  and  is  inserted  into  the  base  of  the  metacarpal 
bone  of  the  middle  finger.  Its  tendon  is  lodged  in  the  same  groove 
on  the  radius  with  that  of  the  extensor  carpi  radialis  longior. 


POSTERIOR  REGION  OF  THE  FOREARM. 


383 


Fig.  116. 


The  EXTENSOR  COMMUNIS  DiGiTORUM  arises  from  the  external 
condyle  by  a  common  tendon  with  the  preceding  and  two  follow- 
ing muscles,  from  the  intermnscular  septa  and  deep  fascia ;  and 
divides  into  four  tendons,  which  are  inserted  into  the  second  and 
third  phalanges  of  the  fingers.  At  the  metacarpo-phalangeal 
articulation  each  tendon  becomes  narrow  and  thick,  and  sends  a 
thin  fasciculus  upon  each  side  of  the  joint.  It  then  spreads  out, 
and  receiving  the  tendon  of  the  lumbricales  and  some  tendinous 
fasciculi  from  the  interossei,  forms  a  broad  aponeurosis,  which 
covers  the  whole  of  the  posterior  aspect  of  the  finger.  At  the 
first  phalangeal  joint  the  aponeurosis  divides  into  three  slips. 
The  middle  slip  is  inserted  into  the  base  of  the 
second  phalanx,  and  the  two  lateral  portions 
are  continued  onwards  on  each  side  of  the 
joint,  to  be  inserted  into  the  last.  Little 
oblique  tendinous  slips  connect  the  tendons 
of  the  ring  with  the  middle  and  little  finger  as 
they  cross  the  back  of  the  hand. 

The  EXTENSOR  MINIMI  DIGITI  (auricularis) 
is  an  off-set  from  the  extensor  communis.  It 
assists  in  forming  the  tendinous  expansion  on 
the  back  of  the  little  finger,  and  is  inserted 
into  the  last  two  phalanges.  It  is  to  this 
muscle  that  the  little  finger  owes  its  power  of 
separate  extension  ;  and  from  being  called  into 
action  when  the  point  of  the  finger  is  intro- 
duced into  the  meatus  of  the  ear,  the  muscle 
was  called  by  the  older  writers  "  auricularis." 

The  EXTENSOR  CARPI  ULNARIS  arises  from 
the  external  condyle  by  the  common  tendon, 
from  the  border  of  the  ulna,  and  from  the  deep 
fascia.  Its  tendon  passes  through  the  pos- 
terior groove  in  the  ulna,  to  be  inserted  into 
the  base  of  the  metacarpal  bone  of  the  little 
finger. 

The  ANCONEUS  is  a  small  triangular  muscle, 
having  the  appearance  of  being  a  continuation 
of  the  triceps  ;  it  arises  from  the  outer  condyle, 
and  is  insertedinto  theolecranon  and  triangular 
surface  of  the  upper  extremity  of  the  ulna. 

THB  ARRANGEMENT  OP  THE  EXTENSOR  TENDON  UPON  THE  DORSAL  SURFACE 
OF  A  FINGER. — 1.  The  metacarpal  bone  of  the  middle  finger-  2.  The  extensor 
tendon  expanding  into  a  broad  aponeurosis,  which  divides  into  three  slips.  3. 
The  middle  slip,  inserted  into  the  base  of  the  second  phalanx.  4.  The  two 
lateral  slips,  inserted  into  the  base  of  the  third  phalanx.  5,  5.  Two  dorsal  in- 
terossei, showing  their  bifid  origin,  6,  6,  and  inserted  by  an  aponeurotic  expan- 
sion into  the  sides  of  the  extensor  tendon.  7.  The  second  lumbricalis  muscle, 
also  inserted  into  the  side  of  the  extensor  tendon. 


384 


THE   DISSECTOR. 


Fig.  117. 


When  these  muscles  have  been  examined,  the  extensor  communis 
digitorum,  extensor  minimi  digiti,  and  extensor  carpi  ulnaris  should  be 
divided,  and  the  ends  drawn  aside,  to  bring  into  view  the  deep  layer, 
which  consists  of  five  muscles : — 

Supinator  brevis, 

Extensor  ossis  metacarpi  pollicis, 

primi  internodii  pollicis, 

secundi  internodii  pollicis, 

indicis. 

The  SUPINATOR  BREVIS  cannot  be  seen  in  its  entire  extent,  until 
the  radial  extensors  of  the  carpus  are  di- 
vided from  their  origin.  It  arises  from 
the  external  condyle,  external  lateral  and 
orbicular  ligament,  and  from  the  ulna ;  it 
winds  around  the  upper  part  of  the  radius 
to  be  inserted  into  the  upper  third  of  its 
oblique  line.  The  posterior  interosseous 
artery  and  nerve  are  seen  perforating  the 
lower  border  of  this  muscle. 

The  EXTENSOR  OSSIS  METACARPI  POL- 
LICIS is  placed  immediately  below  the 
supinator  brevis.  It  arises  from  the 
ulna,  interosseous  membrane,  and  radius, 
and  is  inserted,  as  its  name  implies,  into 
the  base  of  the  metacarpal  bone  of  the 
thumb.  Its  tendon  passes  through  the 
groove  immediately  in  front  of  the  styloid 
process  of  the  radius. 

The  EXTENSOR  PRIMI  INTERNODII  POL- 
LICIS, the  smallest  of  the  muscles  in  this 
layer,  arises  from  the  interosseous  mem- 
brane and  radius,  and  passes  through 
the  same  groove  with  the  extensor  ossis 
metacarpi,  to  be  inserted  into  the  base 
of  the  first  phalanx  of  the  thumb. 

The    EXTENSOR     SECUNDI     INTERNODII 

POLLICIS  arises  from  the  ulna  and  inter- 
osseous membrane.  Its  tendon  passes 
through  a  distinct  groove  in  the  radius, 
and  is  inserted  into  the  base  of  the  last 
phalanx  of  the  thumb. 

THE  DEEP  LAYER  OF  MUSCLES  ON  THE  POSTERIOR  ASPECT  OP  THE  FORE- 
ARM.— 1.  The  lower  part  of  the  humerus.  2.  The  olecranon.  3.  The  ulna. 
4.  The  anconeus  muscle.  5.  The  supinator  brevis  muscle.  6.  The  extensor 
ossis  metacarpi  pollicis.  7.  The  extensor  primi  internodii  pollicis.  8.  The  ex- 
tensor secundi  internodii  pollicis.  9.  The  extensor  indicis.  10.  The  first,  dorsal 
interosseous  muscle.  The  other  three  dorsal  interossei  are  seen  between  the 
metacarpal  bones  of  their  respective  fingers. 


POSTERIOR  REGION  OF  THE  FOREARM.  385 

The  EXTENSOR  INDICIS  arises  from  the  ulna  as  high  up  as  the 
extensor  ossis  metacarpi  pollicis,  and  inferiorly  from  the  interos- 
seous  membrane.  Its  tendon  is  inserted  into  the  aponeurosis 
formed  by  the  common  extensor  tendon  of  the  index  finger. 

When  the  posterior  surface  of  the  lower  extremities  of  the  radius  and 
ulna  is  examined,  a  number  of  grooves  will  be  seen,  through  which  the 
tendons  of  the  muscles  of  the  posterior  region  of  the  forearm  pass  to  their 
destination  upon  the  hand.  In  the  subject,  the  posterior  annular  liga- 
ment forms  for  them  a  number  of  distinct  sheaths.  Their  relative  position 
from  radius  to  ulna  must  be  attentively  studied.  Into  the  base  of  the 
styloid  process  of  the  radius  is  inserted  the  tendon  of  the  supinator  longus. 
Immediately  in  front  of  the  styloid  process  is  a  groove  which  lodges  the 
tendons  of  the  extensor  ossis  metacarpi  and  primi  internodii ;  immediately 
behind  it  another,  broad  and  shallow,  for  the  tendons  of  the  extensor 
carpi  radialis  longior  and  brevior,  which  are  crossed  obliquely  by  a  super- 
ficial sheath  in  the  annular  ligament  for  the  extensor  secundi  internodii. 
Further  inwards  is  a  small  groove  for  the  tendon  of  the  extensor  indicis, 
and  a  large  one  for  the  extensor  communis.  Upon  the  ulna  is  a  groove 
for  the  extensor  minimi  digiti  and  extensor  carpi  ulnaris. 

ACTIONS. — The  anconeus  is  associated  in  its  action  with  the  triceps  ex- 
tensor cubiti ;  it  assists  in  extending  the  forearm  upon  the  arm.  The 
supinator  longus  and  brevis  effect  the  supination  of  the  forearm,  and 
antagonize  the  two  pronators.  The  extensores  carpi  radialis,  longior  and 
brevior,  and  ulnaris  extend  the  wrist  in  opposition  to  the  two  flexors  of 
the  carpus.  The  extensor  communis  digitorum  restores  the  fingers  to 
the  straight  position,  after  being  flexed  by  the  two  flexors,  sublimis  and 
profuudus.  The  extensor  ossis  metacarpi,  primi  internodii,  and  secundi 
internodii  pollicis,  are  the  especial  extensors  of  the  thumb,  and  serve  to 
balance  the  actions  of  the  flexor  ossis  metacarpi,  flexor  brevis,  and  flexor 
longus  pollicis.  The  extensor  indicis  gives  the  character  of  extension  to 
the  index  finger,  and  is  hence  named  indicator,  and  the  extensor  minimi 
digiti  supplies  that  finger  with  the  power  of  exercising  a  distinct  extension. 

The  VESSELS  and  NERVES  of  the  posterior  region  of  the  forearm 
are,  the  posterior  interosseous  artery  and  nerve. 

The  posterior  interosseous  artery  may  now  be  seen  issuing  from 
between  the  contiguous  borders  of  the  supinator  brevis  and  ex- 
tensor ossis  metacarpi  pollicis,  or  piercing  the  fibres  of  the  former. 
Its  course  and  distribution  will  be  found  described  at  page  380. 

The  posterior  interosseous  nerve,  commencing  at  the  bifurca- 
tion of  the  musculo-spiral,  in  front  of  the  external  condyle  of 
the  humerus  (page  371),  pierces  the  supinator  brevis  on  its  an- 
terior aspect,  and  passes  through  the  substance  of  the  muscle 
to  its  lower  part.  It  then  escapes  from  the  muscle,  and  after 
giving  off  several  muscular  branches,  dips  between  the  extensor 
primi  and  secundi  internodii,  to  reach  the  interosseous  mem- 
brane upon  which  it  descends  to  the  wrist-joint,  On  the  wrist 
it  forms  a  gangliform  enlargement,  which  distributes  filaments 
to  the  numerous  articulations  of  the  carpus.  The  posterior 
interosseous  nerve  supplies  all  the  muscles  of  the  posterior  region 
33 


386 


THE  DISSECTOR. 


of  the  forearm,  with  the  exception  of  the  supinator  longus,  ex- 
tensor carpi  radialis  longior,  and  anconeus. 

PALM  OF  THE  HAND. 

To  dissect  the  palm  of  the  hand,  make  an  incision  from  the  wrist  to 
the  root  of  the  middle  finger,  and  bound  it  by  a  transverse  incision  carried 
across  the  roots  of  the  fingers.  Raise  the  integument  by  beginning  at  the 
angles,  and  in  dissecting  the  ulnar  flap  be  careful  not  to  injure  or  remove 
the  palmaris  brevis  muscle.  Afterwards  carry  an  incision  along  the 
middle  of  each  finger,  and  turn  the  integument  aside. 

The  palmaris  brevis  muscle  and  the  cutaneous  branches  of  the  median 
and  ulnar  nerve  should  now  be  examined. 

The  PALMARIS  BREVIS  is  a  thin  plane  of  muscular  fibres,  about 
an  inch  in  width,  which  arises  from  the  annular  ligament  and 

Fig.  118. 

1.  The  annular  ligament.  2,  2. 
The  origin  and  insertion  of  the  ab- 
ductor pollicis  muscle  ;  the  middle 
portion  has  been  removed.  3.  The 
flexor  ossis  metacarpi,  or  opponens 
pollicis.  4.  One  portion  of  the  flexor 
brevis  pollicis.  5.  The  deep  portion 
of  the  flexor  brevis  pollicis.  6.  The 
adductor  pollicis.  7,  7.  The  lum- 
bricales  muscles,  arising  from  the 
deep  flexor  tendons,  upon  which  the 
numbers  are  placed.  The  tendons 
of  the  flexor  sublimis  have  been  re- 
moved from  the  palm  of  the  hand. 

8.  One  of  the  tendons  of  the  deep 
flexors  passing  between  the  two  ter- 
minal slips  of  the  tendon  of  the  flexor 
sublimis  to  reach  the  last  phalanx. 

9.  The  tendon  of  the  flexor  longus 
pollicis,  passing  between  the  two  por- 
tions of  the  flexor  brevis  to  the  last 
phalanx.     10.  The  abductor  minimi 
digiti.     11.  The  flexor  brevis  minimi 
digiti.  The  edge  of  the  adductor  ossis 
metacarpi,  or  adductor  minimi  digiti, 
is  seen  projecting  beyond  the  inner 

border  of  the  flexor  brevis.    12.  The  prominence  of  the  pisiform  bone.    13.  The 
first  dorsal  interosseous  muscle. 


palmar  fascia,  and  passes  transversely  inwards  to  be  inserted  into 
the  integument  of  the  inner  border  of  the  hand. 

The  superficial  branch  of  the  median  nerve,  and  the  cutaneous  palmar 
branch  of  the  ulnar  nerve,  have  been  already  described  at  page  381.  The 
former,  besides  supplying  the  palm  of  the  hand,  sends  a  few  filaments  to 
the  ball  of  the  thumb. 

The  palmar  fascia,  which  is  brought  into  view  by  the  removal 
of  the  superficial  fascia  and  fat,  consists  of  three  portions,  central 
and  two  lateral.  The  lateral  portions  are  thin,  and  inclose  the 


PALM   OP  THE   HAND.  387 

muscles  of  the  borders  of  the  hand.  The  central  portion  occupies 
the  middle  of  the  palm,  and  is  strong  and  tendinous  :  it  is  narrow 
at  the  wrist,  where  it  is  attached  to  the  annular  ligament  and 
receives  the  insertion  of  the  tendon  of  the  palmaris  longus,  and 
broad  over  the  heads  of  the  raetacarpal  bones,  where  it  divides 
into  four  processes,  each  of  which  subdivides  to  embrace  the  root 
of  the  corresponding  finger.  These  processes  are  attached  upon 
the  middle  line  to  the  sheath  of  the  tendons,  and  at  the  side  of 
each  finger  to  the  lateral  and  transverse  ligaments.  The  fascia 
is  strengthened  at  its  point  of  division  into  slips  by  strong  fasci- 
culi of  transverse  fibres,  and  the  arched  interval  left  between  each 
pair  of  slips  gives  passage  to  the  tendons  of  the  flexor  muscles. 
The  arches  between  the  fingers  transmit  the  digital  vessels  and 
nerves,  and  lumbricales  muscles. 

The  palmar  fascia  may  now  be  removed,  in  doing  which,  care  should 
be  taken  to  avoid  dividing  the  superficial  palmar  arch  or  its  branches, 
and  these  latter,  with  their  accompanying  branches  of  the  median  nerve, 
may  be'  cleared  by  the  removal  of  the  cellular  tissue  and  fat.  This  dis- 
section brings  into  view  the  muscles  of  the  palm. 

The  MUSCLES  of  the  palm  of  the  hand  are  arranged  in  three 
groups :  a  radial  or  thenar  group  belonging  to  the  thumb  ;  an 
ulnar  or  hypothenar  group  to  the  little  finger ;   and  a  palmar 
group  situated  in  the  middle  of  the  palm. 
The  muscles  of  the  radial  group  are  the — 
Abductor  pollicis, 
Flexor  ossis  metacarpi  (opponens), 
Flexor  brevis  pollicis, 
Adductor  pollicis. 

The  ABDUCTOR  POLLICIS  is  a  small,  thin  muscle,  which  arises 
from  the  trapezium  bone  and  annular  ligament.  It  is  inserted 
into  the  base  of  the  first  phalanx  of  the  thumb. 

This  muscle  must  be  divided  from  its  origin,  and  turned  aside,  in  order 
to  see  the  next. 

The  FLEXOR  ossis  METACARPI  (opponens  pollicis)  arises  from 
the  trapezium  and  annular  ligament,  and  is  inserted  into  the 
whole  length  of  the  metacarpal  bone. 

The  flexor  ossis  metacarpi  may  now  be  divided  from  its  origin  and 
turned  aside,  in  order  to  show  the  next  muscle. 

The  FLEXOR  BREVIS  POLLICIS  consists  of  two  portions,  between 
which  lies  the  tendon  of  the  flexor  longus  pollicis.  The  external 
portion  arises  from  the  trapezium  and  annular  ligament ;  the 
internal  portion  from  the  trapezoides  and  os  magnum.  They  are 
both  inserted  into  the  base  of  the  first  phalanx  of  the  thumb, 
having  a  sesamoid  bone  in  each  of  their  tendons  to  protect  the 
joint. 


888  THE  DISSECTOR. 

The  next  muscle  is  brought  into  view  by  drawing  aside  the  flexor 
brevis  pollicis  on  the  one  side,  and  the  tendons  of  the  long  flexors  on  the 
other.  It  cannot  be  fully  seen  until  the  latter  hav.e  been  removed  at  a 
subsequent  part  of  the  dissection. 

The  ADDUCTOR  POLLICIS  is  a  triangular  muscle;  it  arises  by  a 
broad  origin  from  the  metacarpal  bone  of  the  middle  finger ;  and 
the  fibres  converge  to  its  insertion  into  the  base  of  the  first  pha- 
lanx of  the  thumb  conjointly  with  the  inner  head  of  the  flexor 
brevis. 

The  muscles  of  the  ulnar  group  are  the — 
Abductor  minimi  digit!, 
Flexor  brevis  minimi  digiti, 
Adductor  ossis  metacarpi  (opponens). 

The  ABDUCTOR  MINIMI  DIGITI  is  a  small  tapering  muscle  which 
arises  from  the  pisiform  bone,  where  it  is  continuous  with  the 
tendon  of  the  flexor  carpi  ulnaris ;  and  it  is  inserted  into  the  base 
of  the  first  phalanx  of  the  little  finger,  and  the  expansion  of  the 
extensor  tendon. 

This  muscle  may  be  divided  through  the  middle  and  its  ends  turned 
aside,  which  will  bring  into  view  the  two  next  muscles. 

The  FLEXOR  BREVIS  MINIMI  DIGITI  is  a  small  muscle  arising 
from  the  unciform  bone  and  annular  ligament,  and  inserted  into 
the  base  of  the  first  phalanx.  It  is  sometimes  wanting. 

The  ADDUCTOR  ossis  METACARPI,  or  adductor  minimi  digiti 
(opponens),  arises  from  the  unciform  bone  and  annular  ligament, 
and  is  inserted  into  the  whole  length  of  the  metacarpal  bone  of 
the  little  finger. 

The  muscles  of  the  middle  palmar  region  are  the — 
Lumbricales, 
Interossei. 

To  bring  the  lumbricales  into  view,  the  tendons  of  the  flexor  sublimis 
should  be  snipped  across  at  the  annular  ligament,  and  drawn  from  under 
the  superficial  palmar  arch  towards  the  fingers ;  the  tendons  of  the  deep 
flexor  are  then  exposed,  with  which  the  lumbricales  are  connected. 

The  LUMBRICALES,  four  in  number,  are  accessories  to  the  deep 
flexor  muscles.  They  arise  from  the  radial  side  of  the  tendons 
of  the  deep  flexor,  and  are  inserted  into  the  aponeurotic  expan- 
sion of  the  extensor  tendons  on  the  radial  side  of  the  fingers. 
These  small  muscles  often  present  varieties  of  origin,  such  as 
arising  by  two  heads,  or  being  connected  with  other  than  the 
radial  border  of  the  tendons. 

The  tendons  of  the  deep  flexor  may  now  be  cut  through  at  the  annular 
ligament,  and  drawn  towards  the  fingers.  In  making  this  section,  a  loose 
synovial  membrane  which  incloses  the  tendons  of  both  flexors  in  their 
passage  beneath  the  annular  ligament,  and  extends  for  a  short  distance 
above  and  below  that  ligament,  will  be  divided.  When  these  tendons  are 


PALM   OF  THE   HAND.  389 

removed,  the  palmar  interossei  will  be  brought  into  view.    Before  examin- 
ing them,  however,  it  may  be  convenient  to  study  the  vessels  and  nerves. 

The  PALMAR  INTEROSSEI,  three  in  number,  are  placed  upon  the 
metacarpal  bones,  rather  than  between  them.  They  arise  from 
the  base  of  the  raetacarpal  bone  of  one  finger,  and  are  inserted 
into  the  base  of  the  first  phalanx  and  aponeurotic  expansion  of 
the  extensor  tendon  of  the  same  finger.  The  first  belongs  to  the 
index  finger,  the  second  to  the  ring  finger,  and  the  third  to  the 
little  finger,  the  middle  finger  being  omitted. 

The  dorsal  interossei  are  seen  from  the  palmar  side  of  the  hand,  occu- 
pying the  spaces  between  the  metacarpal  bones;  but  they  are  best 
examined  by  turning  to  the  dorsal  side. 

The  DORSAL  INTEROSSEI,  four  in  number,  are  situated  in  the 
four  spaces  between  the  metacarpal  bones.  They  are  bipenniform 
muscles,  and  arise  by  two  heads,  from  adjoining  sides  of  the 
bases  of  the  metacarpal  bones.  They  are  inserted  into  the  base 
of  the  first  phalanges,  and  into  the  aponeurosis  of  the  extensor 
tendons. 

The  first  is  inserted  into  the  index  finger,  and  from  its  use  is 
called  abductor  indicts;  the  second  and  third  are  inserted  into  the 
middle  finger,  compensating  its  exclusion  from  the  palmar  group  ; 
the  fourth  is  attached  to  the  ring  finger;  so  that  each  finger  is 
provided  with  two  interossei,  with  the  exception  of  the  little 
finger,  as  may  be  shown  by  means  of  a  table,  thus  :  — 

r  j     £          f°ne  dorsal  (abductor  indicis), 
Index  finger, 


Middle  finger,  two  dorsal. 

„.      -  (one  dorsal, 

Ring  finger, 


Little  finger,     remaining  palmar. 

The  radial  artery  passes  into  the  palm  of  the  hand  between  the 
two  heads  of  the  first  dorsal  interosseous  muscle  and  the  perfo- 
rating branches  of  the  deep  palmar  arch,  between  the  heads  of  the 
other  dorsal  interossei. 

ACTIONS.  —  The  actions  of  the  muscles  of  the  hand  are  expressed  in  their 
names.  Those  of  the  radial  group  belong  to  the  thumb,  and  prpvide  for 
three  of  its  movements,  abduction,  adduction,  and  flexion,  The  ulnar 
group,  in  like  manner,  are  subservient  to  the  same  motions  of  the  little 
finger  ;  and  the  interossei  are  abductors  and  adductors  of  the  several 
fingers.  The  lumbricales  are  accessory  in  their  actions  to  the  deep 
flexors:  they  were  called  by  the  earlier  anatomists  fidicinii,  i.  e.  fiddlers' 
muscles,  from  an  idea  that  they  might  effect  the  fractional  movements  by 
which-  the  performer  is  enabled  to  produce  the  various  notes  on  that 
instrument, 

In  relation  to  the  axis  of  the  hand  (Fig.  119),  the  four  dorsal  interossei 
are  abductors,  and  the  three  palmar  adductors.  It  will  therefore  be  seen 
that  each  finger  is  provided  with  its  prpper  adductor  and  abduptor,  two 

33* 


390 


THE   DISSECTOR. 


flexors,  and  (with  the  exception  of  the  middle  and  ring  fingers)  two 
extensors.     The  thumb  has  moreover  a  flexor  and  extensor  of  the  nieta- 

Fig.  119.  A  DIAGRAM,  SHOWING  THE  ADBUCTOR 

AND  ADDUCTOR  MUSCLES  OF  THE  HAND, 
AND  THE  ATTACHMENTS  AND  ACTIONS  OF 
THE  INTEROSSEI,  The  middle  finger  is 
made  longer  than  the  rest,  in  order  to 
mark  the  central  axis  of  the  hand,  to 
which  the  movements  of  abduction  and 
adduction  are  referable.  The  dotted 
lines  represent  the  six  abductor  muscles, 
and  the  plain  lines  the  four  adductors. — 
1.  The  abductor  pollicis,  arising  from 
the  scaphoid  bone.  2.  The  adductor 
pollicis,  arising  from  the  whole  length 
of  the  middle  metacarpal  bone.  3.  The 
first  dorsal  interosseous,  the  abductor  of 
the  index  finger  :  all  the  dorsal  interossei 
arise  by  two  heads,  as  is  seen  in  the 
diagram.  4.  The  first  palmar  interos- 
seous, the  adductor  of  the  index  finger. 
5,  5.  The  second  and  third  dorsal  in- 
terossei muscles,  both  abductors  of  tho 
middle  finger.  6.  The  second  palmar 
interosseous,  adductor  of  the  ring-finger. 
7.  The  fourth  dorsal  interosseous,  abductor  of  the  ring-finger.  8.  The  third 
palmar  interosseous,  adductor  of  the  little  finger.  9.  The  abductor  of  the  little 
finger,  arising  from  the  pisiform  bone. 

carpal  bone  ;  and  the  little  finger  a  flexor  of  the  metacarpal  bone  without 
an  extensor. 

The  VESSELS  of  the  palm  of  the  hand  are  the  termination  of 
the  ulnar,  forming  the  superficial  palmar  arch,  and  the  termina- 
tion of  the  radial  forming  the  deep  palmar  arch,  with  their  com- 
panion veins  (venae  comites). 

The  TJLNAR  ARTERY  crosses  the  annular  ligament  by  the  side 
of  the  pisiform  bone,  and  curves  across  the  middle  of  the  palm 
to  the  ball  of  the  thumb,  where  it  terminates  by  inosculating 
with  the  superficialis  voles,  a  branch  of  the  radial. 

The  branches  of  the  ulnar  artery  are,  a  communicating  branch 
and  four  digital  arteries. 

The  communicating  or  deep  branch  arises  close  to  the  annular 
ligament,  and  dips  between  the  abductor  minimi  digiti  and  flexor 
brevis  to  inosculate  with  the  termination  of  the  deep  palmar 
arch.  It  is  accompanied  by  the  deep  palmar  branch  of  the  ulnar 
nerve. 

The  digital  branches,  fouj?  In  number,  are  given  off  from  the 
convexity  of  the  superficial  palmar  arch.  The  first  and  smallest 
is  distributed  to  the  ulnar  side  of  the  little  finger.  The  other 
three  are  short  trunks,  which  divide  between  the  heads  of  the 
metacarpal  bones,  and  form  the  collateral  branch  pf  the  radial 


PALM   OF   THE   HAND.  391 

side  of  the  little  finger,  the  collateral  branches  of  the  ring  and 
middle  fingers,  and  the  collateral  branch  of  the  ulnar  side  of  the 
index  finger.  On  the  last  phalanx,  the  collateral  arteries  com- 
municate and  form  an  arch,  from  which  numerous  branches  are 
given  off  to  the  tip  of  the  finger. 

The  RADIAL  ARTERY  enters  the  palm  of  the  hand  between  the 
two  heads  of  first  dorsal  interosseous  muscle,  and  crossing  the 
palmar  interossei  to  the  base  of  the  metacarpal  bone  of  the  little 
finger,  terminates  by  inosculating  with  the  communicating  branch 
of  the  ulnar.  It  thus  constitutes  the  deep  palmar  arch  which 
lies  near  the  basis  of  the  metacarpal  bones,  while  the  superficial 
arch  lies  over  the  distal  third  of  those  bones,  the  two  arches  being 
separated  by  the  tendons  of  the  superficial  and  deep  flexors,  the 
lumbricales,  and  the  median  nerve. 

The  branches  of  the  radial  artery  in  the  palm  of  the  hand  are 
the— 

Princeps  pollicis,  Perforantes, 

Radialis  indicia,  Recurrentes. 

Interosseae, 

The  princeps  pollicis,  the  great  artery  of  the  thumb,  passes 
along  the  metacarpal  bone  of  the  thumb,  between  the  first  dorsal 
interosseous  (abductor  indicis)  and  flexor  brevis  pollices  to  the 
base  of  the  first  phalanx  ;  and  between  the  two  heads  of  the  lat- 
ter muscle,  in  the  groove  of  the  tendon  of  the  flexor  longus,  it 
divides  into  two  collateral  branches  for  the  palmar  borders  of  the 
thumb. 

The  radialis  indicis,  the  digital  branch  of  the  radial  side  of  the 
index  finger,  is  directed  inwards  between  the  abductor  indicis  and 
the  flexor  brevis  and  adductor  pollicis  to  the  side  of  the  finger, 
along  which  it  is  distributed,  forming  its  radial  collateral  artery. 
Near  its  origin  it  gives  off  a  small  branch  (more  frequently  a 
direct  branch  of  the  radial),  which  inosculates  with  the  super- 
ficial palmar  arch. 

The  interossecB  palmares,  three  or  four  in  number,  are  branches 
of  the  deep  palmar  arch  ;  they  pass  forward  upon  the  interossei 
muscles,  and  inosculate  with  the  digital  branches  of  the  superfi- 
cial arch,  opposite  the  heads  of  the  metacarpal  bones. 

The  perforantes,  three  in  number,  pass  directly  backwards  be- 
tween the  heads  of  the  dorsal  interossei  muscles,  and  inosculate 
with  the  dorsal  interosseous  arteries. 

The  recurrent  branches  of  the  deep  palmar  arch  pass  upwards 
in  front  of  the  wrist-joint,  and  inosculate  with  the  arterial  arch 
formed  by  the  anterior  carpal  arteries. 

The  NERVES  of  the  palm  of  the  hand  are  the  ulnar  and  median. 

The  ULNAR  NERVE,  crossing  the  annular  ligament  with  the 


392  THE   DISSECTOR. 

ulnar  artery,  immediately  divides  into  a  superficial  and  deep 
branch. 

The  superficial  palmar  branch,  after  giving  some  filaments  to 
the  palmaris  brevis  and  inner  border  of  the  hand,  divides  into 
three  branches,  which  are  distributed,  one  to  the  ulnar  side  of  the 
little  finger,  one  to  the  adjoining  borders  of  the  little  and  ring 
fingers,  and  a  communicating  branch  to  join  the  median  nerve. 

The  deep  palmar  branch  passes  between  the  abductor  and  flexor 
minimi  digiti  to  the  deep  palmar  arch,  supplying  the  muscles  of 
the  little  finger,  the  interossei  palmar  and  dorsal,  the  two  ulnar 
lumbricales,  adductor  pollicis,  and  inner  head  of  the  flexor  brevis 
pollicis. 

The  MEDIAN  NERVE,  after  passing  beneath  the  annular  ligament, 
is  spread  out  and  flattened,  and  divides  into  a  muscular  and  five 
digital  branches. 

The  muscular  branch  is  distributed  to  the  abductor  pollicis, 
flexor  ossis  metacarpi,  and  external  head  of  the  flexor  brevis. 

The  five  digital  nerves  are  thus  disposed :  two  pass  outwards 
to  the  thumb  and  supply  its  borders ;  the  third  passes  along  the 
radial  side  of  the  index  finger,  sending  a  twig  to  the  first  lumbri- 
calis  in  its  course ;  the  fourth  subdivides  for  the  supply  of  the 
adjacent  sides  of  the  index  and  middle  fingers,  and  gives  a  twig 
to  the  second  lumbricalis ;  the  fifth  receives  a  filament  of  com- 
munication from  the  ulnar  nerve,  and  supplies  the  collateral 
branches  of  the  middle  and  ring  fingers. 

On  the  fingers,  the  digital  nerves  lie  to  the  inner  side  of,  and 
superficially  to,  the  arteries,  and  terminate  by  dividing  into  nume- 
rous twigs  for  their  sentient  extremities,  and  the  structures  en- 
gaged in  the  production  of  the  nails.  Near  the  base  of  the 
first  phalanx  each  nerve  gives  off  a  dorsal  branch,  which  takes 
its  course  along  the  dorsal  border  of  the  finger. 


CHAPTER    VIII. 

THE    LOWER    EXTREMITY. 

BEFORE  commencing  the  dissection  of  the  lower  extremity,  the 
student  will  carefully  reflect  upon  the  objects  of  his  proposed  dis- 
section, and  particularly  upon  the  practical  application  of  the  in- 
formation which  he  is  seeking  to  acquire.  The  lower  extremity 
comprises  all  that  portion  of  the  body  which  forms  the  lower 
limb,  and  is  bounded  above  by  the  external  surface  of  the  pelvis. 
It  consists  of  a  thigh,  leg,  and  foot  j  of  the  hip,  knee,  ankle, 


THE  LOWER  EXTREMITY.  393 

tarsal,  metatarsal,  and  digital  joints  ;  of  a  complicated  apparatus 
of  muscles ;  of  the  femoral,  popliteal,  tibial,  pedal,  and  plantar 
arteries  ;  of  veins,  lymphatics,  nerves,  bones,  and  ligaments. 

Now  all  these  structures  are  liable  to  injury  ;  and  the  surgeon, 
upon  such  an  occurrence,  is  called  upon  to  remedy  the  accident, 
to  apply  the  knowledge  that  he  shall  have  gained,  through  the 
aid  of  his  eyes  and  hands,  in  the  dissecting-room.  Suppose  the 
accident  be  one  involving  deep  and  important  parts  without 
affecting  the  surface,  or  exposing  to  the  eyes  the  structure  which 
may  be  injured  :  in  such  a  case  the  surgeon  has  recourse  to  the 
comparative  form  and  position  of  the  adjoining  limb  ;  but  cir- 
cumstances may  render  this  comparison  unavailing ;  and  he  is 
then  obliged  to  recall  the  observations  he  may  chance  to  have 
made  during  his  anatomical  studies.  Depend  upon  it,  that  a 
sound  knowledge  of  the  relations  of  the  different  portions  of  the 
limbs  will  ever  be  found  of  the  highest  possible  value  to  the  man 
who  is  suddenly  called  to  the  aid  of  a  wounded  fellow-creature. 
Indeed,  such  a  knowledge  should  b«  considered  as  the  leading 
characteristic  of  the  accomplished  surgeon. 

Starting  with  reflections  such  as  these,  the  student  will  per- 
ceive that  other  observations  are  necessary  to  him  in  addition  to 
those  which  arise  out  of  the  mere  dissection  of  the  component 
parts  of  the  limb  which  he  is  about  to  study.  The  thigh  may  be 
dislocated  at  the  hip,  or  at  the  knee ;  the  muscles,  or  their  ten- 
dons, may  be  ruptured  ;  the  arteries  may  be  wounded  or  diseased, 
requiring  that  incisions  of  considerable  extent  or  depth  should 
be  made  in  their  course,  and  a  ligature  placed  around  them  ;  or 
nerves  may  be  ganglionated,  and  demand  removal ;  lastly,  the 
whole  limb  may  be  disorganized,  and  call  for  amputation.  In 
each  and  every  of  these  circumstances,  relief  is  simply  and  effect- 
ually bestowed,  if  the  operator  be  well  acquainted  with  the  situa- 
tion and  dissection  of  the  various  structures  implicated  in  the 
accident  or  disease  ;  and  these  are  to  be  learnt  only  in  the  dis- 
secting-room by  careful  observation  and  manipulation. 

Having  the  lower  extremity  extended  on  the  table  before  him, 
and  the  leg  everted,  let  the  student  carry  a  line  (Fig.  120,  i)  from 
the  extreme  point  of  the  anterior  superior  spinous  process  of  the 
ilium  to  the  symphysis  pubis,  and  then  another,  2,  from  the  middle 
of  the  preceding  to  that  projection  upon  the  inner  condyle  of  the 
femur,  which  gives  attachment  to  the  internal  lateral  ligament  of 
the  knee-joint ;  this  will  mark  the  course  of  the  femoral  artery. 
If  the  leg  be  perfectly  straight,  without  inversion  or  eversion, 
the  line  must  be  carried  to  the  apex  of  the  patella.  Again,  if  a 
line,  3,  be  drawn  from  the  spinous  process  of  the  pubis  along 
the  inner  border  of  the  thigh  to  the  projection  on  the  internal 
condyle,  a  second  line,  4,  drawn  from  the  anterior  superior 


394 


THE  DISSECTOR. 


120. 


spinous  process  of  the  ilium,  and  crossing  the  former  at  the  mid- 
dle of  the  thigh,  will  mark  the  direction  of  the  upper  margin  of 
the  sartorius  muscle,  and  inclose  a  triangular  space  (Scarpa's), 
which  is  bounded  above  by  Poupart's  liga- 
ment. Within  this  triangle,  which  cor- 
responds with  the  axillary  space  in  the 
upper  limb,  the  position  of  the  femoral 
artery  may  be  distinguished  by  a  groove, 
and  may  be  laid  bare  and  secured,  in  any 
part  of  the  line  2,  which  marks  its  course  ; 
the  usual  situation  for  ligature  of  the  fe- 
moral artery  (Scarpa's  operation),  in  pop- 
liteal aneurism,  being  at  the  point  where 
the  upper  margin  of  the  sartorius  crosses 
its  course,  the  border  of  this  muscle  form- 
ing the  natural  guide  for  the  direction  of 
the  incision.  At  the  pubic  angle  of  this 
triangular  space,  is  situated  the  saphenous 
opening,  11,  through  which  the  sac  of  fe- 
moral hernia  is  protruded.  In  rare  cases, 
the  femoral  artery  is  tied  below  the  lower 
border  of  the  sartorius  muscle  (Hunter's 
operation)  ;  under  such  circumstances,  a 
space,  varying  from  one  inch  to  one  inch 
and  a  half,  and  parallel  to  the  oblique  line, 
should  be  allowed  for  the  breadth  of  the 
sartorius,  and  the  incision  commenced  im- 
mediately below  this  border,  6,  still  fol- 
lowing the  original  line  of  its  course. 

Besides  these,  there  is  another  point 
of  importance  to  the  surgeon,  in  the  con- 

THE  THIGH  TURNED  UPON  ITS  OUTER  SIDE  AS  IN  DISSECTING  IT. — 1.  A  line 
drawn  from  the  anterior  superior  spine  of  the  ilium  to  the  spine  of  the  pubis ; 
these  two  points  are  represented  by  crosses.  2.  A  second  line  extended  from 
the  middle  of  the  preceding  to  the  tubercle  on  the  inner  condyle  of  the  femur. 
This  line  marks  the  direction  of  the  femoral  artery.  3.  A  third  line,  drawn 
from  the  spine  of  the  pubis  to  the  tubercle  on  the  inner  condyle  of  the  femur. 
4.  A  fourth  line  drawn  from  the  spine  of  the  ilium  to  the  middle  of  line  3  ; 
this  line  marks  the  upper  border  of  the  sartorius  muscle,  and  is  the  direction 
for  the  incision  in  securing  the  artery  in  the  upper  third  of  its  course.  5.  The 
outline  of  the  sartorius  muscle.  6.  The  direction  of  the  incision  in  operating 
upon  the  femoral  artery,  below  the  sartorius  muscle,  shown  by  a  dotted  line. 
7.  A  line  drawn  from  the  trochanter  major  to  the  spine  of  the  ilium.  8. 
Another  line  drawn  from  the  trochanter  major  to  the  crest  of  the  ilium.  9. 
The  internal  saphenous  vein.  10.  The  superficial  epigastric  and  superficial  cir- 
cumflexa  ilii  veins,  converging  to  open  into  it  previously  to  its  entrance  into  the 
saphenous  opening.  11.  The  saphenous  opening  in  the  fascia  lata.  12.  The 
ext-  ^al  cutaneous  nerve.  13.  The  middle  cutaneous  nerves,  branches  of  the 
Crural. 


ANTERIOR  FEMORAL  REGION.  395 

sideration  of  the  proper  projections  on  the  surface  of  the 
limb,  viz:  the  apophysis  named  trochanter  major.  For  it  is 
this  prominence  that  marks  the  altered  position  of  the  limb  in 
dislocations  or  diseases  of  the  hip-joint,  or  fractures  about  the 
neck  of  the  femur.  It  is  a  point  little  liable  to  variation  from 
strength  or  muscularity  of  the  limb  ;  but  is  necessarily  more 
prominent  and  more  sharply  defined  in  an  emaciated  person.  A 
line,  8,  drawn  from  the  upper  point  of  the  trochanter  major  to 
the  most  convex  part  of  the  crest  of  the  ilium,  and  another,  Y, 
extended  from  the  same  point  to  the  anterior  superior  spinous 
process,  may  be  compared  with  the  same  admeasurements  on  the 
opposite  limb. 

An  important  measurement  of  the  thigh,  for  the  detection  of 
dislocation,  is  obtained  by  extending  a  line  from  the  anterior 
superior  spinous  process  of  the  ilium  to  the  apex  of  the  patella, 
and  comparing  its  length  with  that  on  the  opposite  limb.  If 
shortening  be  found  to  exist,  whilst  the  distance,  8,  between  the 
trochanter  major  and  the  crest  of  the  ilium  is  the  same  on  both 
sides  of  the  body,  then  the  cause  of  the  diminution  of  length 
must  exist  in  the  bone,  and  be  the  result  of  fracture.  This  may 
be  determined  by  another  measurement,  made  between  the  apex 
of  the  trochanter  major  and  the  lower  point  of  the  patella. 

Let  it  not  be  said  that  these  directions  are  too  obvious  to 
deserve  attention :  they  must  be  followed  carefully ;  and  before 
the  student  commences  his  dissection,  he  should  have  himself 
made  and  repeated  the  observations  here  advised  ;  have  impressed 
well  upon  his  memory  the  relative  position  of  each  landmark ; 
and  have  cut  down  upon  the  artery  at  various  points.  By  such 
means  he  will  gain  confidence  in  his  knowledge  and  precision  in 
the  performance  of  surgical  operations.  Again,  in  displacement 
of  the  ends  of  the  bone  from  fracture  of  the  femur,  it  is  of  the 
greatest  importance  to  their  proper  adjustment,  that  he  be  well 
acquainted  with  the  position  of  the  patella  in  relation  to  the 
spines  of  the  ilium  and  pubes. 

The  lower  extremity  is  divided  anatomically  into  several  dis- 
tinct compartments  or  regions,  the  separate  and  relative  study  of 
which  serves  materially  to  facilitate  the  student's  apprehension  of 
the  whole.  The  regions  of  the  thigh  are,  the  anterior  femoral, 
internal  femoral,  gluteal,  posterior  femoral,  and  popliteal;  of  the 
leg,  the  anterior  tibial,  fibular,  sural  or  superficial  posterior 
tibial,  and  deep  posterior  tibial;  of  the  foot,  the  dorsal  and 
plantar  regions. 

ANTERIOR  FEMORAL  REGION. 

The  dissection  of  the  anterior  femoral  region  is  best  commenced  by 
making  an  incision  (Fig.  120,  i),  from  the  anterior  superior  spinous  process 


396  THE   DISSECTOR. 

of  the  ilium  along  the  line  of  Poupart's  ligament  to  the  spinous  process  of 
the  pubis,  then  carrying  a  second,  2,  along  the  course  of  the  femoral  artery 
to  the  inner  condyle  of  the  femur,  and  bounding  it  inferiorly  by  a  third, 
carried  transversely  across  the  head  of  the  tibia.  It  may  be  convenient 
to  make  a  fourth  incision  across  the  middle  of  the  thigh  so  as  to  diminish 
the  extent  of  surface  opened  at  once,  and  enable  the  student  to  concen- 
trate his  attention  in  the  first  instance  upon  the  most  important  part  of 
the  front  of  the  thigh,  namely,  the  triangular  hollow  space  which  con- 
tains the  femoral  vessels  and  the  saphenous  opening.  The  student  then 
nips  up  the  integument  with  his  forceps  at  the  upper  angle,  and  dissects 
back  that  layer  so  as  to  expose  the  superficial  fascia  beneath,  and  form  a 
flap  upon  the  outer  side  of  the  limb.  He  then  turns  to  the  opposite  side, 
and  repeats  the  same  proceeding. 

But  the  student  who  handles  a  scalpel  for  the  first  time,  will  not  find 
its  application  so  easy  as  this  description  would  lead  him  to  infer.  If  he 
examine  the  edge  of  his  blade  attentively  with  a  lens,  he  will  perceive 
that  it  is  actually  a  microscopic  saw.  Now  a  saw  divides  by  being  drawn 
across  the  material  to  be  cut ;  and  no  direct  force  applied  to  the  saw, 
would  carry  it  through  the  substance  without  this  motion.  Let  him 
apply  this  reasoning  to  his  scalpel,  it  must  be  handled  lightly,  and  drawn 
without  pressure  across  the  textures  to  be  divided :  if  he  uses  force  and 
pressure,  the  best  edge  would  be  useless  in  his  hands.  The  art  of  dis- 
secting with  neatness  and  operating  with  dexterity,  owes  much  to  the 
good  understanding  existing  between  the  knife  and  the  hand  ;  and  the 
best  operators  have  ever  been  the  best  dissectors. 

If  the  student  have  reflected  the  integument  well,  he  will  have 
exposed  the  superficial  fascia,  which  may  be  known  by  its  soft 
yellow  surface,  studded  with  lobules  of  fat,  surrounded  by  the 
white  areolae  of  cellular  tissue  in  which  they  are  contained.  The 
under  surface  of  the  integument,  the  corium  of  the  skin,  will 
appear  quite  white,  and  present  a  number  of  depressions,  corre- 
sponding with  the  fatty  depositions  in  the  superficial  fascia. 

The  SUPERFICIAL  FASCIA  is  composed  of  two  layers,  between 
which  are  situated  the  cutaneous  vessels  and  nerves.  To  examine 
these  an  incision  should  be  made  by  the  side  of  the  saphenous 
vein,  and  the  superficial  layer  dissected  outwards  and  upwards 
towards  Poupart's  ligament,  over  which  it  may  be  traced  into  the 
subcutaneous  covering  of  the  abdomen.  This  dissection  is  com- 
paratively easy  in  the  groin,  from  the  number  of  superficial  ves- 
sels; nerves,  and  lymphatics  which  are  found  in  that  region,  but 
lower  down  the  thigh,  the  separation  of  the  layers  is  impracti- 
cable. The  deep  layer  is  interposed  between  the  superficial  ves- 
sels and  the  fascia  lata,  and  closes  the  saphenous. opening;  the 
perforation  of  the  latter  portion  of  the  superficial  fascia  by  nume- 
rous lymphatic  vessels  has  gained  for  it  the  appellation  of  cribri- 
form fascia. 

The  parts  to  be  examined  in  the  superficial  fascia  are,  the 
inguinal  glands,  the  three  small  arteries,  superficial  circumflexa 
ilii,  superficial  epigastric  and  superior  external  pudic,  the  internal 


CUTANEOUS  NERVES  OF   THE  THIGH.  397 

saphenous  vein  and  its  tributaries,  the  crnral  portions  of  the  ilio- 
inguinal  and  genito-crural  nerves,  the  external,  middle,  and  inter- 
nal cutaneous  nerves,  and  in  the  lower  part  of  the  thigh  the 
superficial  branch  of  the  auastoraotica  magna  artery,  the  internal 
saphenous  nerve,  and  the  extensive  nervous  interlacement  situated 
around  the  front  of  the  knee,  the  plexus  patellae. 

The  inguinal  glands  are  situated  along  the  line  of  Poupart's 
ligament,  and  near  the  termination  of  the  saphenous  vein ;  the 
former  receive  the  lymphatic  vessels  from  the  abdomen  and  genital 
organs ;  the  latter,  of  larger  size,  receive  the  lymphatics  of  the 
lower  limb. 

The  three  small  arteries,  the  superficial  circumflexa  ilii,  the 
superficial  epigastric,  and  the  superior  external  pudic,  are  the 
first  branches  of  the  femoral  artery.  They  pierce  the  deep  fascia 
immediately  beneath  Poupart's  ligament,  and  are  distributed  to 
the  skin,  superficial  fascia,  and  inguinal  glands :  the  circumflexa 
ilii  taking  its  course  along  Poupart's  ligament  towards  the  crest 
of  the  ilium ;  the  epigastric  ascending  upon  the  abdomen  towards 
the  umbilicus ;  and  the  pudic  passing  inwards  to  the  scrotum,  or 
labia  pudendi. 

The  internal  saphenous  vein  (Fig.  120,  9),  (so^^f,  perspicuous, 
obvious),  of  considerable  size,  sometimes  consisting  of  two  parallel 
trunks,  receives  its  current  of  blood  from  the  superficial  veins  of 
the  inner  side  of  the  foot,  leg,  and  thigh,  along  which  it  runs, 
and  terminates  in  the  femoral  vein  near  the  pubic  extremity  of 
Poupart's  ligament,  by  passing  through  an  aperture  in  the  deep 
fascia,  named,  from  its  office,  saphenous  opening,  11.  Just  as 
the  vein  curves  inwards  to  enter  this  opening,  it  receives  a  number 
of  small  veins,  10,  which  converge  from  the  abdomen,  hip,  and 
genital  organs.  These  vessels  play  a  conspicuous  part  in  femoral 
hernia,  and,  therefore,  must  not  be  passed  over  without  remark. 
The  saphenous  vein  is  accompanied  by  superficial  lymphatic  ves- 
sels throughout  the  whole  of  its  course. 

The  cutaneous  nerves  will  be  found :  the  ilio-inguinal  to  the 
inner  side  of  the  saphenous  opening;  the  genito-crural  just  exter- 
nally to  the  saphenous  opening  ;  the  two  branches  of  the  middle 
cutaneous  nerve  in  the  middle  of  the  front  of  the  thigh  ;  the  inter- 
nal cutaneous,  its  three  branches,  in  the  line  of  the  internal  saphe- 
nous vein  ;  and  the  external  cutaneous  along  the  outer  border  of 
the  thigh. 

The  crural  portion  of  the  ilio-inguinal  nerve  is  the  continua- 
tion of  that  nerve,  after  it  has  escaped  with  the  spermatic  cord 
from  the  external  abdominal  ring.  It  terminates  in  the  integu- 
ment of  the  upper  part  of  the  thigh,  internally  to  the  saphenous 
opening,  after  having  supplied  the  scrotum.  The  ilio-iuguiiial 
nerve  proceeds  from  the  first  lumbar  nerve. 
34 


398  THE   DISSECTOR. 

The  crural  branch  of  the  genito-crural  nerve  pierces  the  fascia 
lata  a  little  below  Poupart's  ligament,  and  just  externally  to  the 
femoral  artery  from  the  sheath  of  which  it  escapes.  It  is  dis- 
tributed to  the  integument  as  far  as  the  middle  of  thigh,  and  com- 
municates with  the  middle  cutaneous  nerve.  The  genito-crural 
nerve  proceeds  from  the  second  lumbar  nerve. 

The  middle  cutaneous  nerve  is  a  branch  of  the  anterior  crural ; 
it  pierces  the  fascia  lata  about  three  inches  below  Poupart's  liga- 
ment, and  divides  into  two  branches,  which  are  distributed  to  the 
integument  of  the  front  of  the  thigh  as  far  as  the  knee.  One  or 
both  of  these  branches  sometimes  pierce  the  sartorius  muscle. 

The  internal  cutaneous  nerve,  also  a  branch  of  the  anterior 
crural,  passes  inwards  in  front  of  the  sheath  of  the  femoral  artery, 
and  after  giving  off  three  cutaneous  filaments,  which  pierce  the 
fascia  lata  and  follow  the  course  of  the  internal  saphenous  vein, 
divides  into  an  anterior  and  an  inner  branch.  The  anterior 
branch  pierces  the  fascia  lata  at  the  lower  third  of  the  thigh, 
near  the  internal  saphenous  vein,  which  it  follows  to  the  inner 
side  of  the  knee  and  divides  into  two  terminal  twigs.  The  inner 
branch  pierces  the  fascia  lata  on  the  inner  side  of  the  knee,  and  is 
distributed  to  the  integument  along  the  inner  side  of  the  leg. 

The  external  cutaneous  nerve  (  Fig.  120,  12),  is  derived  from  the 
second  lumbar  nerve,  and  pierces  the  fascia  lata  about  two  inches 
below  the  anterior  superior  spine  of  the  ilium,  where  it  divides 
into  two  branches,  one  of  which  (posterior)  crosses  the  tensor 
vaginae  femoris  muscle  to  the  outer  and  posterior  side  of  the  thigh, 
and  is  distributed  to  the  integument  in  that  region  ;  the  anterior 
branch,  after  passing  downwards  for  several  inches  in  a  sheath  of 
the  fascia  lata,  divides  into  two  twigs,  which  are  distributed  to 
the  integument  of  the  outer  border  of  the  thigh,  and  to  the  knee- 
joint. 

The  long  saphenous  nerve  pierces  the  deep  fascia  and  becomes 
superficial  at  the  side  of  the  knee ;  it  is  accompanied  by  the  super- 
ficial branch  of  the  anastomotica  magna  artery. 

The  cutaneus  patellae,  a  branch  of  the  long  saphenous,  becomes 
superficial  a  little  higher  than  the  parent  trunk,  and  assists  in  the 
formation  of  the  plexus  patellae,  by  means  of  its  communications 
with  the  other  cutaneous  nerves  of  the  knee. 

When  these  structures  have  been  well  examined,  the  deep  layer  of 
superficial  fascia  may  be  removed,  in  order  to  bring  into  view  the  deep 
fascia. 

The  DEEP  FASCIA  of  the  thigh,  from  being  the  most  extensive 
in  the  body,  is  named  fascia  lata.  It  is  an  extremely  dense  mem- 
brane, consisting  of  glistening  tendinous  fibres,  disposed  longitu- 
dinally and  circularly  around  the  limb ;  is  thickest  on  the  outer  side 
of  the  thigh,  and  thinner  on  its  inner  side.  The  fascia  lata  en- 


FASCIA  LATA — CRIBRIFORM  FASCIA.  399 

velops  the  whole  of  the  muscle  of  the  thigh,  and  sends  processes 
inwards,  which  form  distinct  sheaths  for  each.  It  is  attached 
above  to  the  prominent  points  about  the  pelvis,  viz :  to  the  pubes, 
Poupart's  ligament,  crest  of  the  ilium,  sacrum,  and  ischium ;  below, 
to  the  heads  of  the  tibia  and  fibula ;  behind,  to  the  linea  aspera. 
Besides  these,  it  has  two  muscular  attachments,  one  by  means  of 
the  tensor  vaginae  femoris  ;  the  other,  through  the  gluteus  maxi- 
mus.  It  is  perforated  at  several  points  for  the  passage  of  cuta- 
neous nerves,  and  near  the  pubes  is  the  saphenous  opening. 

The  existence  of  this  opening  (Fig.  120,  1 1),  causes  the  divi- 
sion of  the  upper  part  of  the  fascia  lata  into  two  portions,  an 
iliac  portion  situated  towards  the  ilium,  and  a  pubic  portion  to- 
wards the  pubes.  The  iliac  portion  is  attached  along  Poupart's 
ligament,  as  far  as  the  spine  of  the  pubes;  from  this  point  it  is 
reflected  downwards,  in  a  curved  direction,  forming  a  sharp  edge, 
called  the  falciform  process.  The  edge  of  the  falciform  process 
immediately  overlays  and  is  reflected  upon  the  sheath  of  the  fe- 
moral vessels ;  and  the  lower  extremity  of  the  curve  is  continuous 
with  the  pubic  portion.  The  pubic  portion  is  also  attached  to 
the  spine  of  the  pubes,  and  along  the  pectineal  line,  as  far  as  the 
inner  border  of  the  psoas  muscle :  here  it  divides  into  two  layers, 
which  embrace  that  muscle  and  the  iliacus,  and  are  then  lost  in 
the  fascial  coverings  surrounding  the  muscles  on  the  outer  side 
of  the  thigh. 

From  this  description,  it  will  be  obvious  that  the  iliac  portion, 
being  attached  to  Poupart's  ligament,  must  be  on  a  plane  consi- 
derably anterior  to  the  pubic  portion  which  is  attached  to  the 
bone;  and  it  is  between  the  two  that  the  femoral  vessels  are 
placed,  inclosed  in  their  sheath.  It  follows  also  from  this  dispo- 
sition that  the  saphenous  opening  is  oblique  in  its  direction  with 
regard  to  these  two  layers  of  fascia.  It  is,  moreover,  closed  by 
some  dense  bands  of  cellular  tissue,  which  are  perforated  by  a 
number  of  minute  openings  for  the  transmission  of  the  superficial 
lymphatic  vessels  of  the  lower  extremity,  and  are  hence  named 
cribriform  fascia  (cribrum,  a  sieve).  This  cribriform  fascia 
would  be  altogether  unworthy  the  notice  of  the  dissector,  were  it 
not  for  the  arbitrary  importance  attached  to  every  fibre  of  mem- 
brane or  process  of  fascia  that  may  possess  the  slightest  relation 
to  the  protrusion  of  intestine  from  the  cavity  of  the  abdomen. 
For  this  reason  it  is  that  the  saphenous  opening  is  so  urgently 
recommended  to  the  student's  attention ;  and  the  cribriform  fascia, 
from  its  position,  must  necessarily  form  one  of  the  coverings  of 
the  femoral  hernia. 

The  student  may  now  remove  the  fascia  lata,  by  dissecting  it 
from  its  loose  cellular  attachment  to  the  muscles,  following  always 
the  course  of  their  fibres.  If  the  student  would  dissect  well,  he 


400 


TIIE  DISSECTOR. 


Fig.  121. 


must  treasure  this  rule  as  a  golden  maxim :  "  Muscles  must 
always  be  dissected  in  the  course  of  their  fibres."  And,  let  us 
remind  him  again  (for  we  cannot  too  strenuously  insist  upon  the 
application  of  the  principles  of  dissection  to  the  operations  of 
surgery),  that,  in  the  living  body,  the  same  rule  must  be  rigidly 
adhered  to,  if  a  successful  issue  be  desired. 

Muscles  of  the  Anterior  Femoral  Region. 

The  muscles  of  the  anterior  femoral  region  are  arranged  in 
two  groups,  an  anterior  group,  consisting 
of  six  muscles  ;  and  an  internal  group  of 
seven,  as  follows : — 

Anterior  Group. 

Tensor  vaginae  femoris. 

Sartorius. 

Rectus. 

Yastus  internus. 

Yastus  externus. 

Crureus. 

Internal  Group. 

Iliacus  internus. 

Psoas  magnus. 

Pectineus. 

Adductor  longus. 

Adductor  brevis. 

Adductor  magnus. 

Gracilis. 

As  soon  as  these  two  tables  are  got  by  heart, 
the  student  may  commence  the  dissection  of  the 
muscles  which  they  represent. 

The  TENSOR  VAGINAE  FEMORIS  (stretcher 
of  the  sheath  of  the  thigh),  is  a  short  flat 
muscle,  situated  on  the  outer  side  of  the 
hip.  It  arises  from  the  crest  of  the  ilium, 
near  its  anterior  superior  spinous  process, 
and  {^inserted  between twolayers  of  thefascia 
lata  at  about  one-fourth  down  the  thigh. 

The  SARTORIUS  (tailor's  muscle),  is  a  long 
ribbon-like  muscle,  arising  from  the  ante- 

THE  MUSCLES  OF  THE  ANTERIOR  FEMORAL  REGION. — 1.  The  crest  of  the 
ilium.  2.  Its  anterior  superior  spinous  process.  3.  The  gluteus  medius.  4. 
The  tensor  vaginae  femoris ;  its  insertion  into  the  fascia  lata  is  shown  inferiorly. 
5.  The  sartorius.  6.  The  rectus.  7.  The  vastus  externus.  8.  The  vastus  in- 
ternus. 9.  The  patella.  10.  The  iliacus  internus.  11.  The  psoas  magnus. 
12.  The  pectineus.  13.  The  adductor  longus.  14.  Part  of  the  adductor  magnus. 
15.  The  gracilis. 


MUSCLES — ANTERIOR  FEMORAL  REGION.  401 

rior  superior  spinous  process  of  the  ilium  and  from  the  notch 
immediately  below  that  process  ;  it  crosses  obliquely  the  upper 
third  of  the  thigh,  descends  behind  the  inner  condyle  of  the 
femur,  and  is  inserted  by  an  aponeurotic  expansion  into  the  inner 
tuberosity  of  the  tibia.  This  expansion  covers  in  the  insertion 
of  the  tendons  of  the  gracilis  and  semitendinosus  muscles.  The 
inner  border  of  the  sartorius  muscle  is  the  guide  to  the  opera- 
tion for  tying  the  femoral  artery  in  the  middle  of  its  course ;  and 
the  outer  boundary  of  Scarpa's  triangular  space. 

The  RECTUS  (straight)  muscle  is  fusiform  in  its  shape  and  bi- 
penniform  in  the  disposition  of  its  fibres  :  it  arises  by  two  round 
tendons  ;  one  from  the  anterior  inferior  spinous  process  of  the 
ilium,  the  other  from  the  upper  lip  of  the  acetabulum.  It  is  in- 
serted by  a  broad  and  strong  tendon  into  the  upper  border  of  the 
patella.  It  is  more  correct  to  consider  the  patella  as  a  sesarnoid 
bone,  developed  within  the  tendon  of  the  rectus ;  and  the  liga- 
mentum  patellae  as  the  continuation  of  the  tendon  to  its  insertion 
into  the  tubercle  of  the  tibia. 

The  rectus  must  now  be  divided  through  its  middle,  and  the  two  ends 
turned  aside,  to  bring  clearly  into  view  the  next  muscles. 

The  next  three  muscles  are  generally  considered  collectively 
under  the  name  of  triceps  extensor  criiris.  Adopting  this  view, 
the  muscle  surrounds  the  whole  of  the  femur,  except  the  rough 
line  (linea  aspera)  upon  its  posterior  aspect.  Its  division  into 
three  parts  is  not  well  defined  ;  the  fleshy  mass  upon  each  side 
being  distinguished  by  the  names  of  vastus  internus  and  exter- 
nus,  the  middle  portion  by  that  of  crureus. 

The  VASTUS  EXTERNUS,  narrow  below  and  broad  above,  arises 
from  the  base  of  the  trochanter  major,  the  outer  surface  of  the 
femur  and  outer  lip  of  the  linea  aspera  and  from  the  intermuscu- 
lar  fascia  ;  and  passes  down  to  be  inserted  into  the  outer  border 
of  the  patella  ;  or  rather,  by  means  of  the  ligamentum  patellae, 
into  the  tubercle  of  the  tibia,  conjointly  with  the  rectus  and  two 
following  muscles. 

The  VASTUS  INTERNUS,  broad  below  and  narrow  above,  arises 
from  the  anterior  intertrochanteric  line,  inner  surface  of  the  fe- 
mur, inner  lip  of  the  linea  aspera,  and  intermuscular  fascia,  and 
is  inserted  into  the  inner  border  of  the  patella.  By  its  mesial 
border  it  is  blended  with  the  crureus. 

The  CRUREUS  (crus,  the  leg)  arises  from  the  anterior  inter- 
trochanteric line  and  anterior  surface  of  the  femur  to  within  two 
inches  of  the  patella.  It  is  continuous  by  its  inner  border  with 
the  vastus  internus,  and  is  inserted  into  the  upper  border  of  the 
patella  ;  its  tendon  occupying  its  cutaneous  aspect. 

When  the  crureus  is  divided  from  its  insertion,  a  small  mus- 

34* 


402  THE  DISSECTOR. 

cular  fasciculus  is  often  seen  upon  the  lower  part  of  the  femur  ; 
this  fasciculus  is  inserted  into  the  pouch  of  synovial  membrane 
that  extends  upwards  from  the  knee-joint  behind  the  patella,  and 
is  named,  from  its  situation,  sub-crureus.  It  would  seem  to  be 
intended  to  support  the  synovial  membrane. 

ACTIONS. — The  tensor  vaginae  femoris  renders  the  fascia  lata  tense,  and 
slightly  inverts  the  limb.  The  sartorius  flexes  the  leg  upon  the  thigh, 
and,  continuing  to  act,  the  thigh  upon  the  pelvis,  at  the  same  time  carry- 
ing the  leg  across  that  of  the  opposite  side,  into  the  position  in  which 
tailors  sit ;  hence  its  name.  Taking  its  fixed  point  from  below,  it  assists 
the  extensor  muscles  in  steadying  the  leg  for  the  support  of  the  trunk. 
The  other  four  muscles  have  been  collectively  named  quadriceps  extensor, 
from  their  similarity  of  action.  They  extend  the  leg  upon  the  thigh, 
and  obtain  a  great  increase  of  power  by  their  attachment  to  the  patella, 
which  acts  as  a  fulcrum.  Taking  their  fixed  point  from  the  tibia,  they 
steady  the  femur  upon  the  leg  ;  and  the  rectus,  by  being  attached  to  the 
pelvis,  serves  to  balance  the  trunk  upon  the  lower  extremity. 

Internal  Femoral  Region. 

The  origins  of  the  iliacus  and  psoas  muscles  being  situated  within  the 
abdomen,  the  entire  muscles  cannot  be  seen  in  this  dissection  ;  but  as  a 
part  of  them  quits  that  cavity  to  be  inserted  into  the  femur,  that  portion 
necessarily  belongs  to  the  anatomy  of  the  thigh. 

The  ILIACUS  INTERNUS  is  a  flat,  radiated  muscle  :  it  arises  from 
the  inner  concave  surface  of  the  ilium,  and,  after  joining  with  the 
tendon  of  the  psoas,  is  inserted  into  the  trochanter  minor  of  the 
femur.  A  few  fibres  of  this  muscle  proceed  from  the  sacrum, 
and  others  from  the  capsular  ligament  of  the  hip-joint. 

The  PSOAS  MAGNUS  (^oa,  lumbus,  a  loin),  situated  by  the  side 
of  the  vertebral  column  in  the  loins,  is  a  long  fusiform  muscle. 
It  arises  from  the  bodies  and  bases  of  the  transverse  processes  of 
the  last  dorsal  and  all  the  lumbar  vertebra.  It  also  takes  its 
origin  from  the  intervertebral  substances  and  from  a  series  of 
tendinous  arches  attached  to  the  vertebra,  and  intended  for  the 
protection  of  the  lumbar  vessels  and  branches  of  the  sympathetic 
nerve,  in  their  passage  between  the  muscle  and  the  bone.  The 
tendon  of  the  psoas  magnns  unites  with  that  of  the  iliacus,  and 
the  conjoined  tendon  is  inserted  into  the  posterior  part  of  the 
trochanter  minor. 

Two  synovial  bursae  are  found  in  relation  with  the  last  two 
muscles  :  the  first,  of  considerable  size,  is  situated  between  their 
under  surface  and  the  capsule  of  the  hip-joint ;  the  other,  much 
smaller,  is  interposed  between  the  conjoined  tendon  and  the  an- 
terior part  of  the  trochanter  minor. 

The  PECTINEUS  is  a  flat  and  quadrangular  muscle  ;  it  arises  from 
the  pectineal  line  (pecten,  a  crest)  of  the  os  pubis,  and  from  the 
surface  of  bone  in  front  of  that  line ;  and  is  inserted  into  the  line 


MUSCLES — INTERNAL  FEMORAL  REGION.  403 

leading  from  the  anterior  intertrochanteric  line  to  the  linea  aspera 
of  the  femur. 

The  ADDUCTOR  LONGUS  (adducere,  to  draw  to),  the  most  super- 
ficial of  the  three  adductors,  arises  by  a  round  and  thick  tendon 
from  the  front  surface  of  the  os  pubis,  immediately  below  the 
angle  of  that  bone  ;  and,  assuming  a  flattened  and  expanded  form 
as  it  descends,  is  inserted  into  the  middle  third  of  the  linea  aspera. 

The  pectineus  and  adductor  longus  form  the  inner  boundary  of  the 
triangular  space  of  Scarpa,  in  which  the  femoral  vessels  and  nerves  are 
lodged.  They  must  be  divided,  the  pectineus  near  its  origin  and  turned 
outwards,  and  the  adductor  longus  through  its  middle,  turning  its  ends 
to  either  side,  to  bring  into  view  the  adductor  brevis. 

The  ADDUCTOR  BREVIS,  placed  behind  the  pectineus  and  adductor 
longus,  is  fleshy,  and  thicker  than  the  adductor  longus  ;  it  arises 
from  the  body  of  the  os  pubis,  and  is  inserted  into  the  line  leading 
from  the  trochanter  minor  to  the  linea  aspera.  It  is  pierced  by 
the  middle  perforating  artery,  and  supports  the  anterior  branch 
of  the  obturator  nerve  and  artery. 

The  adductor  brevis  may  now  be  divided  from  its  origin  and  turned 
outwards,  or  its  inner  two-thirds  may  be  cut  away  entirely,  after  sepa- 
rating the  anterior  branch  of  the  obturator  artery  and  nerve  from  its 
surface.  This  exposes  the  entire  extent  of  the  adductor  magnus,  and  a 
fleshy  mass  of  muscle  which  covers  in  the  obturator  foramen,  the  obtu- 
rator externus. 

The  OBTURATOR  EXTERNUS  muscle  (obturare,  to  stop  up)  arises 
from  the  obturator  membrane,  and  from  the  surface  of  bone  im- 
mediately surrounding  it  anteriorly,  viz:  from  the  ramus  of  the  os 
pubis  and  ischium  :  its  tendon  passes  behind  the  neck  of  the  femur, 
to  be  inserted  with  the  external  rotator  muscles,  into  the  tro- 
chanteric  fossa  of  the  femur. 

Although  this  muscle  belongs  properly  to  another  group  (glutseal  region), 
it  has  been  deemed  consistent  with  the  object  of  this  work  to  describe 
every  organ  which  may  come  beneath  the  observation  of  the  student  in 
the  progress  of  his  dissection,  in  the  situation  which  it  actually  occupies. 

The  ADDUCTOR  MAGNUS  is  a  broad  triangular  muscle,  forming 
a  septum  of  division  between  the  muscles  situated  on  the  anterior 
and  those  on  the  posterior  aspect  of  the  thigh.  It  arises  by  fleshy 
fibres  from  the  ramus  of  the  os  pubis  and  ischium  and  from  the 
side  of  the  tuber  ischii ;  and  radiating  in  its  passage  outwards,  is 
inserted  into  the  whole  length  of  the  linea  aspera,  and  inner  con- 
dyle  of  the  femur.  The  adductor  magnus  is  pierced  by 'five 
openings  :  the  three  superior,  for  the  three  perforating  arteries ; 
and  the  fourth,  for  the  termination  of  the  profunda.  The  fifth  is 
the  large  oval  opening,  in  the  tendinous  portion  of  the  muscle, 
that  gives  passage  to  the  femoral  vessels. 

The  GRACILIS  (slender)  is  situated  along  the  inner  border  of 
the  thigh :  it  arises  by  a  broad,  but  very  thin,  tendon,  from  the 


404  THE   DISSECTOR. 

body  of  the  os  pubis  along  the  edge  of  the  symphysis,  and  from 
the  margin  of  the  ramus  of  the  pubes  and  ischium  ;  and  is  inserted 
by  a  rounded  tendon  into  the  inner  tuberosity  of  the  tibia,  beneath 
the  expansion  of  the  sartorius. 

ACTIONS. — The  iliacus,  psoas,  pectineus,  and  adductor  longus  muscles 
bend  the  thigh  upon  the  pelvis,  and,  at  the  same  time,  from  the  obliquity 
of  their  insertion  into  the  lesser  trochanter  and  linea  aspera,  rotate  the 
entire  limb  outwards :  the  pectineus  and  adductors  adduct  the  thigh 
powerfully ;  and  from  the  manner  of  their  insertion  into  the  linea  aspera, 
they  assist  in  rotating  the  limb  outwards :  the  gracilis  is  likewise  an 
adductor  of  the  thigh,  but  contributes  also  to  the  flexion  of  the  leg,  by  its 
attachment  to  the  inner  tuberosity  of  the  tibia. 

VESSELS  OF  THE  THIGH. 

The  arteries  of  the  anterior  aspect  of  the  thigh  are  next  to  be  examined : 
they  are  best  dissected  by  following  the  branches  through  their  ramifica- 
tions from  the  main  trunk.  The  scalpel  may  be  carried  along  the  side 
of  their  cylinder  without  danger  of  dividing  their  coats  ;  but  if  it  be 
turned  in  the  opposite  direction,  they  must  inevitably  be  cut  across. 
They  are  easily  separated  from  the  cellular  tissue  and  adipose  substance, 
and  from  the  smaller  veins  which  surround  them.  All  the  veins,  ex- 
cepting the  main  trunks,  had  better  be  removed  at  once,  otherwise  their 
intricacy  and  bleeding  will  greatly  interfere  with  the  student's  progress, 
and  confuse  his  dissection. 

FEMORAL  ARTERY. 

The  arteries  situated  on  the  anterior  aspect  of  the  thigh  are 
the  femoral  and  its  branches  :  the  latter  are  as  follows  : — 

Superficial  circumflexa  ilii. 

epigastric. 

Superior  external  pudic. 

Inferior  external  pudic. 

( External  circumflex. 

Profunda  -<  Internal  circumflex. 
(Three  perforating. 

Muscular. 

Anastomotica  magna. 

The  femoral  artery  and  vein  are  inclosed  in  a  sheath,  the 
femoral  sheath,  which  is  broad  and  funnel-shaped  at  Poupart's 
ligament,  but  narrows  to  the  size  of  the  vessels  two  inches  below 
that  point.  The  infundibular  portion  of  the  sheath  is  aponeu- 
rotic  in  structure,  and  is  continuous  with  the  transversalis  and 
iliac  fasciae ;  but  lower  down,  where  it  closely  invests  the  vessels, 
it  consists  of  condensed  cellular  tissue.  In  the  infundibuliform 
portion  of  the  sheath,  the  artery  and  vein  lie  side  by  side,  sepa- 
rated by  a  septum  ;  and  to  the  inner  side  of  the  vein,  also  sepa- 
rated by  a  septum,  is  a  space  occupied  by  a  lymphatic  gland  and 
some  loose  cellular  tissue — the  femoral  or  crural  canal.  Above, 


FEMORAL  ARTERY.  405 

the  femoral  canal  opens  into  the  abdomen  by  an  aperture  which 
is  termed  the  femoral  or  crural  ring  ;  below,  it  is  lost  in  the  con- 
traction of  the  sheath. 

Below  the  infundibular  portion  of  the  femoral  sheath,  two 
nerves,  the  long  saphenous  and  muscular  branch  to  the  vastus  in- 
ternus, both  branches  of  the  anterior  crural,  are  found  in  relation 
with  the  vessels.  Above,  they  lie  to  the  outer  side;  but  lower 
down,  the  long  saphenous  passes  in  front  of  the  artery  and  enters 
the  aponeurotic  sheath  which  incloses  the  vessels. 

These  nerves  are  to  be  borne  in  mind  in  the  operation  for  tying  the 
femoral  artery  in  the  upper  third  of  the  thigh  (Scarpa's  operation).  In 
this  operation  the  incision  (about  three  inches  in  length),  is  made  along 
the  upper  and  inner  edge  of  the  sartorius  muscle,  and  crosses  obliquely 
the  direction  of  the  vessels.  The  integument  is  first  divided,  then  the 
superficial  fascia ;  next  the  deep  fascia,  or  fascia  lata ;  the  edge  of  the 
sartorius  muscle  is  then  to  be  drawn  aside  and  the  sheath  of  the  vessels 
exposed  ;  the  operator  opens  the  sheath  with  care,  to  avoid  injuring  the 
two  nerves  just  referred  to,  and  the  needle  is  placed  around  the  artery, 
taking  care  to  separate  it  as  little  as  possible  from  its  connections.  In 
making  the  first  incision  the  saphenous  vein  must  be  remembered,  lest 
it  be  divided,  and  the  point  of  the  artery  selected  for  the  application  of 
the  ligature  should  be  between  four  and  five  inches  below  Poupart's  liga- 
ment. The  femoral  vein  is  here  altogether  behind  the  artery. 

In  the  operation  below  the  sartorius  (Hunter's  operation),  the  incision, 
three  inches  in  length,  is  made  along  the  lower  and  outer  border  of  the 
sartorius,  in  the  groove  between  that  muscle  and  the  vastus  internus. 
The  parts  cut  through  are  the  same  as  in  Scarpa's  operation ;  the  sarto- 
rius must  be  drawn  upwards  and  inwards ;  and  the  artery  secured  where 
it  lies  under  cover  of  the  aponeurotic  fascia  stretched  across  it  between 
the  adductor  longus  and  magnus  on  the  one  side,  and  the  vastus  internus 
on  the  other. 

The  FEMORAL  ARTERY  runs  down  the  inner  side  of  the  thigh, 
from  Poupart's  ligament,  at  a  point  exactly  midway  between 
the  anterior  superior  spinous  process  of  the  ilium  and  symphysis 
pubis,  to  the  hole  in  the  adductor  magnus,  at  the  junction  of 
the  middle  with  the  inferior  third  of  the  thigh,  where  it  becomes 
the  popliteal  artery.  The  femoral  vein  is  at  first  to  the  inner 
side,  and  upon  the  same  plane  with  the  artery,  but  lower  down ; 
the  vein  becomes  placed  behind  and  rather  to  the  outer  side  of 
the  artery,  and  retains  that  relation  throughout  the  rest  of  its 
course. 

delations. — The  upper  third  of  the  femoral  artery  is  super- 
ficial, being  covered  only  by  the  integument,  superficial  fascia, 
fascia  lata,  and  some  lymphatic  glands.  The  lower  two  thirds 
are  covered  by  the  sartorius  muscle.  To  its  outer  side  the  artery 
rests  against  the  psoas  and  vastus  internus,  and  is  separated  from 
the  anterior  crural  nerve  by  the  breadth  of  the  former  muscle. 
Behind,  it  has  the  psoas  muscle  which  intervenes  between  it  and 
the  hip-joint ;  it  is  next  separated  from  the  pectineus  by  the 


406 


THE   DISSECTOR. 


femoral  vein,  profunda  vein  and  artery,  and  then  lies  on  the 
adductor  longus  to  its  termination.  While  beneath  the  sartorius 
muscle  it  is  placed  in  an  aponeurotic  sheath,  or  canal  formed  by 


Fig.  122. 


A  VIEW  OP  THE  ANTERIOR  AND  IN- 
KER ASPECT  OP  THE  THIGH,  SHOWING 
THE  COURSE  AND  BRANCHES  OP  THE 
FEMORAL  ARTERY. — 1.  The  lower  part 
of  the  aponeurosis  of  the  external 
oblique  muscle  ;  its  inferior  margin  is 
Poupart's  ligament.  2.  The  external 
abdominal  ring.  3,  3.  The  upper  and 
lower  part  of  the  sartorius  muscle  ;  its 
middle  portion  having  been  removed. 
4.  The  rectus.  5.  The  vastus  internus. 
6.  The  patella.  7.  The  iliacus  and 
psoas  ;  the  latter  being  nearest  the  ar- 
tery. 8.  The  pectineus.  9.  The  ad- 
ductor longus.  10.  The  tendinous  canal 
for  the  femoral  artery  formed  by  the 
adductor  magnus,  and  vastus  internus 
muscles.  11.  The  adductor  magnus. 
12.  The  gracilis.  13.  The  tendon  of 
the  semi-tendinosus.  14.  The  femoral 
artery.  15.  The  superficial  circumflexa 
ilii  artery  taking  its  course  along  the 
line  of  Poupart's  ligament,  to  the  crest 
of  the  ilium.  2.  The  superficial  epi- 
gastric artery.  16.  The  two  external 
pudic  arteries,  superficial  and  deep. 
17.  The  profunda  artery  giving  off  18, 
its  external  circumflex  branch ;  and 
lower  down  the  three  perforantes.  A 
small  bend  of  the  internal  circumflex 
artery  (8),  is  seen  behind  the  inner 
margin  of  the  femoral,  just  below  the 
deep  external  pudic  artery.  19.  The 
anastomotica  magna,  descending  to  the 
knee,  upon  which  it  ramifies  (6). 


tendinous  fibres  extended  like  a  bridge  from  the  adductor  longus 
and  magnus  to  the  vastus  internus  ;  this  is  the  aponeurotic  sheath 
through  which  the  long  saphenous  nerve  takes  its  course. 

Branches. — The  superficial  circumflexa  ilii,  superficial  epigas- 
tric, superior  external  pudic,  and  inferior  external  pudic,  are 
four  small  arteries  given  off  from  the  femoral,  immediately  below 
Poupart's  ligament. 

The  superficial  circumflexa  ilii  passes  outwards  beneath  the 
fascia  lata,  and  piercing  that  structure  near  the  anterior  superior 
spine  of  the  ilium,  becomes  cutaneous  and  is  distributed  to  the 


PEOFUNDA  FEMORIS.  407 

integument.  In  its  course  it  sends  off  several  twigs  which  pierce 
the  fascia  to  reach  the  inguinal  glands. 

The  superficial  epigastric,  after  piercing  the  fascia  lata,  ascends 
towards  the  umbilicus  and  inosculates  with  branches  of  the  deep 
epigastric. 

The  superior  external  pudic  artery  passes  inwards  across  the 
spermatic  cord,  and  is  distributed  to  the  penis  and  scrotum  in 
the  male,  and  labia  in  the  female.  It  inosculates  with  the  inter- 
nal pudic  artery. 

The  two  latter  arteries  are  important  in  their  connection  with  hernial 
tumors  occurring  in  this  region  :  I  have  seen  both  of  them  crossing  an 
inguinal,  and  the  latter  ramifying  upon  a  femoral  hernia.  In  tjie  opera- 
tion they  are  liable  to  division  ;  but,  from  their  small  size,  would  cause 
very  little  inconvenience. 

The  inferior  external  pudic  is  given  off  from  the  femoral  a 
little  below  and  sometimes  in  common  with  the  superior  exter- 
nal pudic ;  it  crosses  the  femoral  vein  immediately  below  the 
termination  of  the  internal  saphenous  vein,  and  resting  on  the 
pectineus  reaches  the  inner  border  of  the  thigh  ;  it  then  pierces 
the  fascia  lata  and  is  distributed  to  the  integument  of  the  exter- 
nal organs  of  generation  and  perineum,  communicating  with 
branches  of  the  internal  pudic. 

The  PROFUNDA  FEMORIS  artery  is  given  off  from  the  outer  side 
of  the  femoral,  about  one  inch  and  a  half  below  Poupart's  liga- 
ment. From  its  large  size,  it  may  be  considered  as  a  division  of 
the  femoral  rather  than  a  branch  :  and,  in  this  view,  the  short 
trunk  has  been  called  the  common  femoral  (femoralis  communis), 
and  its  two  divisions,  femoralis  superficialis  and  femoralis  profunda ; 
the  superficial  femoral  being  intended  for  the  supply  of  the  knee 
and  leg,  while  the  profunda  is  distributed  to  the  thigh.  The  pro- 
funda artery  is  best  examined  by  drawing  aside  or  removing  the 
superficial  femoral,  and  dissecting  away  the  femoral  and  profunda 
veins,  that  conceal  the  artery  from  view.  The  adductor  longus 
would  also  be  dissected  from  its  insertion  with  advantage. 

The  course  of  the  profunda  artery  is  downwards  and  back- 
wards, and  a  little  outwards,  behind  the  adductor  longus  muscle; 
it  then  pierces  the  adductor  magnus,  and  is  distributed  to  the 
flexor  muscles  of  the  posterior  part  of  the  thigh. 

Relations. — The  profunda  artery  rests  successively  upon  the 
pectineus,  the  conjoined  tendon  of  the  psoas  and  iliacus,  adductor 
brevis,  and  adductor  magnus  muscles.  To  its  outer  side,  the 
tendinous  insertion  of  the  vastus  internus  muscle  intervenes 
between  it  and  the  femur,  and  in  front  it  is  separated  from  the 
femoral  artery  above  by  the  profunda  vein  and  femoral  vein  ;  and 
below  by  the  adductor  longus  muscle. 


408  THE  DISSECTOR. 

The  branches  of  the  profunda  artery  are  the  external  circum- 
flex, internal  circumflex,  and  three  perforating  arteries. 

The  external  circumflex  artery  passes  outwards  beneath  the 
sartorius  and  rectus,  and  in  front  of  the  crureus  muscle,  passing 
between  the  divisions  of  the  crural  nerve,  and  divides  into  three 
sets  of  branches ;  ascending,  which  pass  upwards  beneath  the 
sartorius,  rectus,  and  tensor  vaginae  fernoris,  and  inosculate  with 
the  terminal  branches  of  the  gluteal  artery ;  descending,  which 
pass  downwards  beneath  the  rectus  muscle  to  inosculate  with  the 
superior  articular  arteries  of  the  popliteal ;  and  middle,  which 
continue  the  original  course  of  the  artery  around  the  thigh,  pierce 
the  vastus  externus,  and  anastomose  with  branches  of  the  ischi- 
atic,  internal  circumflex,  and  superior  perforating  artery.  It 
supplies  the  muscles  on  the  anterior  and  outer  side  of  the  thigh. 

The  internal  circumflex  artery  winds  around  the  inner  side  of 
the  neck  of  the  femur,  passing  between  the  pectineus  and  psoas, 
and  over  the  upper  border  of  the  adductor  brevis  to  the  tendon 
of  the  obturator  externug,  which  it  accompanies  to  the  space 
between  the  quadratus  femoris  and  upper  border  of  the  adductor 
magnus.  While  on  the  obturator  externus  it  gives  off  a  branch 
which  is  distributed  to  that  muscle,  the  adductor  brevis  and  gra- 
cilis,  and  anastomoses  with  the  obturator  artery.  It  next  gives 
off  an  articular  branch  which  enters  the  hip-joint  through  the 
notch  in  the  acetabulum  ;  and  terminates  in  several  branches 
which  inosculate  with  the  ischiatic,  external  circumflex,  and  supe- 
rior perforating  arteries. 

The  superior  perforating  artery  passes  backwards  near  the 
lower  border  of  the  pectineus,  pierces  the  adductor  brevis  and 
magnus  near  the  femur,  and  is  distributed  to  the  posterior  muscles 
of  the  thigh ;  inosculating  freely  with  the  circumflex  and  ischiatic 
arteries,  and  with  the  branches  of  the  middle  perforating  artery. 

The  middle  perforating  artery  pierces  the  tendons  of  the  adduc- 
tor brevis  and  magnus,  and  is  distributed  like  the  superior  ;  inos- 
culating with  the  superior  and  inferior  perforantes.  From  this 
branch  is  given  off  the  nutritious  artery  of  the  femur. 

The  inferior  perforatiny  artery  is  given  off  below  the  adductor 
brevis,  and  pierces  the  tendon  of  the  adductor  magnus,  supplying 
it  and  the  flexor  muscles,  and  inosculating  with  the  middle  per- 
forating artery  above,  and  with  the  articular  branches  of  the 
popliteal  below. 

It  is  through  the  medium  of  the  branches  of  the  profunda, 
which  inosculate  above  with  branches  of  the  internal  iliac,  and 
below  with  those  of  the  popliteal  artery,  that  the  collateral  circu- 
lation is  maintained  in  the  limb  after  ligature  of  the  femoral 
artery. 

We  now  return  to  the  superficial  femoral.     It  gives  off  mus- 


VEINS  OF  FEMORAL  REGION.  409 

cular  branches  throughout  the  whole  of  its  course,  which  supply 
the  muscles  in  immediate  proximity  with  the  artery,  particularly 
those  of  the  anterior  aspect  of  the  thigh.  One  of  these  branches, 
larger  than  the  rest,  arises  from  the  femoral  immediately  below 
the  origin  of  the  profunda,  and  passing  outwards  between  the 
rectus  and  sartorius,  divides  into  branches,  which  are  distributed 
to  all  the  muscles  of  the  anterior  aspect  of  the  thigh.  This  may 
be  named  the  superior  muscular  artery. 

The  anastomotica  magna  arises  from  the  femoral,  near  to  its 
termination  at  the  opening  in  the  adductor  magnus,  and  divides 
into  a  superficial  and  deep  branch.  The  superficial  branch 
accompanies  the  internal  saphenous  nerve  to  the  knee,  and  piercing 
the  fascia  lata  is  distributed  to  the  integument.  The  deep  branch 
passes  onwards  through  the  substance  of  the  vastus  internus 
muscle,  and  resting  on  the  tendon  of  the  adductor  magnus  to  the 
knee,  where  it  inosculates  with  the  internal  articular  branches  of 
the  popliteal,  and  the  recurrent  of  the  anterior  tibial.  It  also 
sends  a  branch  to  the  vastus  internus,  which  supplies  the  syno- 
vial  membrane  of  the  joint,  and  inosculates  with  the  superior 
external  articular  artery  and  external  circumflex. 

When  the  pectineus  muscle  is  divided  through  its  origin  and  turned 
down,  a  small  artery  will  be  seen  issuing  from  the  opening  in  the  upper 
part  of  the  obturator  membrane ;  this  is  the  obturator  artery,  a  branch  of 
the  internal  iliac. 

The  OBTURATOR  artery,  after  passing  through  the  obturator 
foramen,  divides  into  two  branches,  internal  and  external.  The 
internal  branch  curves  inwards  around  the  bony  margin  of  the 
obturator  foramen,  and  distributes  branches  to  the  obturator  and 
adductor  muscles,  inosculating  with  the  internal  circumflex  artery 
of  the  femoral.  The  external  branch  winds  around  the  outer 
margin  of  the  obturator  foramen  to  the  space  between  the  gemel- 
lus  inferior  and  quadratus  femoris,  where  it  inosculates  with  the 
ischiatic  artery.  In  its  course  it  inosculates  also  with  the  internal 
circumflex  artery,  and  sends  a  small  branch  through  the  notch  in 
the  acetabulum,  to  supply  the  ligamentum  teres. 

The  VEINS  of  the  anterior  femoral  region  are  superficial  and 
deep.  The  superficial,  are  the  internal  saphenous,  and  its  tribu- 
taries. The  deep,  are  the  femoral  and  profunda,  with  their  tri- 
butaries. The  femoral  vein  commences  at  the  hole  in  the  adductor 
magnus,  and  ascends  behind  the  artery  to  within  two  inches  of 
Pou part's  ligament,  where  it  receives  the  profunda  vein  ;  it  then 
becomes  placed  to  the  inner  side  of  the  artery,  and  continues  in 
that  position  to  Poupart's  ligament.  After  passing  beneath  the 
ligament,  it  receives  the  name  of  external  iliac  vein.  The  pro- 
funda vein,  commencing  with  the  ultimate  ramifications  of  the 
profunda  artery,  ascends  in  front  of  that  vessel  to  its  origin  from 
35 


410 


THE   DISSECTOR. 


the  common  femoral  artery,  where  it  joins  the  femoral  vein.     The 

tributary  veins  are  those  accompanying  the  branches  of  the  main 

arteries.     They  are  usually  two  to  each  branch,  one  on  either 

side:  hence  they  are   called  vence  comites.     They  communicate 

freely  across  the  cylinder  of  the  artery  by  short  transverse  trunks. 

Yeins  are  considerably  larger  than  the  arteries 

Fig.  123.         which  they  accompany. 

Nerves  of  the  Anterior  Femoral  Region. 

The  student  will  now  direct  his  attention  to 
the  nerves  of  this  region.  They  are  derived 
from  the  lumbar  plexus  :  and  are  the — 

External  cutaneous, 

Genito-crural, 

(Middle  cutaneous, 
Internal  cutaneous, 
Long  saphenous, 
Muscular, 
Obturator. 

The   EXTERNAL   CUTANEOUS   NERVE,    4,   IS   de- 

scribed  with  the  superficial  fascia  at  page  398. 
The  crural  portion  of  the  genito-crural  nerve  ; 
and  the  crural  distribution  of  the  ilio-inguinal 
nerve  have  also  been  described  in  the  same  place. 

The  ANTERIOR  CRURAL  OR  FEMORAL  NERVE,  6, 

is  the  largest  of  the  branches  from  the  lumbar 
plexus.  It  is  formed  by  the  union  of  the  second, 
third,  and  fourth  lumbar  nerves,  passes  beneath 
the  outer  border  of  the  psoas  magnus  muscle, 
and  runs  downwards  in  the  groove  between  that 
muscle  and  the  iliacus  internus  to  Poupart's 
ligament.  It  is  there  separated  from  the  femoral 
artery  by  the  breadth  of  the  psoas  muscle,  usually 
not  more  than  half  an  inch  wide  ;  and  immediately 
below  Poupart's  ligament  divides  into  superficial 
and  deep  branches  :  while  within  the  pelvis  it 
gives  off  several  twigs  to  the  iliacus  muscle,  and 
sends  down  a  branch  to  supply  the  femoral  artery. 
The  superficial  branches  are  the  middle  cu- 

THE  LUMBAR  PLEXUS  WITH  ITS  BRANCHES. — 1.  The  dorsal  lumbar  nerve. 
2.  The  four  upper  lumbar  nerves.  3.  The  two  musculo-cutaneous  nerves, 
branches  of  the  first  lumbar  nerve.  4.  The  external  cutaneous  nerve.  5.  The 
genito-crural  nerve.  6.  The  crural  or  femoral  nerve.  7.  Its  muscular  branches. 
8.  Its  cutaneous  branches,  middle  cutaneous.  9.  Its  descending  or  saphenous 
branches.  10.  The  short  saphenous  nerve.  11.  The  long  or  internal  saphenous. 
12.  The  obturator  nerve. 


OBTURATOR  NERVE.  411 

taneons,  internal  cutaneous,  and  internal  saphenous ;  the  deep 
branches  are  the  muscular  and  articular. 

The  middle  and  internal  cutaneous  nerves  have  been  already 
described ;  page  398. 

The  long  saphenous  or  internal  saphenous  nerve  inclines  in- 
wards to  the  sheath  of  the  femoral  vessels,  and  passes  downwards 
in  front  of  the  sheath  and  beneath  the  aponeurotic  expansion 
which  covers  the  sheath,  to  the  opening  in  the  adductor  magnus. 
It  then  quits  the  femoral  vessels,  and,  continuing  to  descend, 
passes  between  the  tendons  of  the  sartorius  and  gracilis,  and 
reaches  the  internal  saphenous  vein.  By  the  side  of  the  latter  it 
passes  down  the  inner  side  of  the  leg,  in  front  of  the  inner  ankle 
and  along  the  inner  side  of  the  foot  as  far  as  the  great  toe.  The 
branches  of  the  internal  saphenous  are,  one  or  two  in  the  thigh 
to  communicate  with  the  obturator  nerve  and  internal  cutaneous, 
the  three  together  forming  a  plexus  ;  one,  at  the  knee,  the  cu- 
taneous patella,  which  pierces  the  sartorius  muscle  and  is  distri- 
buted to  the  front  of  the  knee,  assisting,  by  its  communications 
with  other  cutaneous  nerves  of  the  knee,  to  form  the  plexus patellce ; 
and  several  cutaneous  twigs  below  the  knee. 

Of  the  deep  branches  of  the  anterior  crural  nerve  the  muscular 
supply  all  the  muscles  of  the  anterior  femoral  region  (excepting 
one)  and  the  pectineus.  The  excepted  muscle  is  the  tensor 
vaginae  femoris,  which  receives  its  nerves  from  the  superior  gluteal. 
The  sartorius  muscle  receives  three  or  four  branches,  which  arise 
with  the  cutaneous  nerves,  and  frequently  are  supplied  by  the 
latter.  The  branch  to  the  vastus  extemus  accompanies  the  de- 
scending branch  of  the  external  circumflex  artery.  The  branch 
to  the  vastus  internus  muscle  (short  saphenous,  of  some  authors, 
from  arising  frequently  in  common  with  the  long  saphenous,  and 
pursuing  a  parallel  course  in  the  upper  part  of  the  thigh)  descends 
upon  the  sheath  of  the  femoral  vessels,  and  beneath  the  aponeurotic 
fascia  of  the  sheath.  It  is  of  large  size,  and  sends  off  several  twigs 
to  the  vastus  internus,  and  a  long  articular  filament  to  the  synovial 
membrane  of  the  knee-joint.  This  latter  accompanies  the  deep 
branch  of  the  anastomotica  magna. 

The  OBTURATOR  NERVE  is  formed  by  a  branch  from  the  third 
and  another  from  the  fourth  lumbar  nerve,  and,  passing  down- 
wards through  the  psoas  muscle  and  bifurcation  of  the  common 
iliac  vessels,  runs  along  the  inner  border  of  the  brim  of  the  pelvis 
to  the  obturator  foramen,  where  it  joins  the  obturator  artery. 
Having  escaped  from  the  pelvis,  it  divides  into  an  anterior  and  a 
posterior  branch. 

The  anterior  branch  passes  in  front  of  the  adductor  brevis  and 
supplies  that  muscle,  the  pectineus,  gracilis,  and  adductor  longus, 
and,  at  the  lower  border  of  the  latter,  unites  with  the  internal 


412  THE  DISSECTOR. 

cutaneous  nerve  and  internal  saphenous  to  form  a  plexus.  In  its 
course  this  nerve  gives  off  an  articular  twig  to  the  hip-joint,  a 
cutaneous  branch  which  pierces  the  fascia  lata  at  the  knee ;  and 
after  communicating  with  the  internal  saphenous  nerve  is  dis- 
tributed to  the  integument  as  far  as  the  middle  of  the  leg ;  and  a 
twig  from  its  termination  to  the  femoral  artery. 

The  posterior  branch  pierces  the  obturator  externus  muscle, 
and  sends  twigs  for  its  supply  as  well  as  the  adductor  magnus 
muscle ;  it  also  sends  down  an  articular  filament  which  accompa- 
nies the  popliteal  artery  to  the  knee-joint. 

A  portion  of  the  obturator  nerve  is  sometimes  given  off  in  an 
irregular  manner,  and  proceeds  in  an  irregular  course.  When  it 
exists,  it  is  either  a  high  division  of  the  obturator,  or  takes  its 
origin  by  separate  cords  from  the  third  and  fourth  lumbar  nerves. 
It  is  called  the  accessory  obturator  nerve ;  passes  down  along  the 
inner  border  of  the  psoas  muscle  to  the  front  of  the  pelvis,  crosses 
the  body  of  the  os  pubis,  and  gets  beneath  the  pectineus.  It  gives 
branches  to  the  pectineus  muscle  and  hip-joint,  and  joins  the 
anterior  branch  of  the  obturator,  forming,  when  of  large  size, 
the  cutaneous  branch  of  that  nerve. 

We  advise  the  student  to  have  made  himself  thoroughly  master  of  this 
region  and  of  each,  before  he  ventures  to  direct  his  attention  to  another, 
and  to  proceed  methodically,  following  with  care  every  line  of  proceeding 
here  pointed  out,  unless,  indeed,  he  can  himself  suggest  a  better  or  one 
more  familiar  to  his  mode  of  study,  for  we  are  well  convinced  that  the 
same  plan  will  not  be  found  advantageous  to  all.  Let  him  question  his 
knowledge  upon  each  of  the  preceding  sections,  and  remark  the  adage 
"Memoria  augetur  ex  colendo." 

FEMORAL  HERNIA. 

After  proceeding,  as  we  have  here  directed,  with  the  common 
anatomy  of  the  anterior  femoral  region,  the  student  may  now  turn 
his  attention  to  the  special  anatomy  of  that  portion  of  the  region 
through  which  the  intestine  finds  its  way  in  femoral  hernia.  With 
this  object  the  sheath  of  the  vessels  should  have  been  left  undis- 
turbed. 

The  sheath  may  now  be  opened,  and  the  parts  contained  within 
the  sheath  and  adjacent  parts  examined.  Stretching  across  from 
the  anterior  superior  spinous  process  of  the  ilium  to  the  spine  of 
the  pubes  is  Poupart's  ligament,  which  forms  an  arch  over  the 
concave  border  of  the  pelvis,  the  crural  or  femoral  arch.  Beneath 
this  arch  will  be  seen  to  pass  a  number  of  important  structures, 
which  are  disposed  in  the  following  order,  from  without  inwards : 
external  cutaneous  nerve,  6  (Fig.  124);  iliacus  internus  muscle,  7; 
anterior  crural  nerve,  8 ;  psoas  maguus  muscle,  9 ;  crural  division  of 
the  genito-crural  nerve,  10;  femoral  artery,  11;  femoral  vein,  12  ; 


FEMORAL   HERNIA.  413 

lymphatic  vessels ;  the  four  latter  being  inclosed  in  a  common 
sheath. 

The  sheath,  13,  14,  of  the  femoral  vessels  is  the  fibrous  covering 
which  invests  the  artery  and  vein  during  their  passage  beneath 

Fig.  124. 


A  SECTION  OP  THE  STRUCTURES  WHICH  LEAVE  THE  PELVIS  THROUGH  THE 
FEMORAL  ARCH; — THE  VESSELS  AND  THEIR  SHEATH  ONLY  BEING  LEFT. — 1. 
Poupart's  ligament,  the  upper  boundary  of  the  femoral  arch.  2.  Its  lower 
boundary,  the  border  of  the  pubis  and  ilium.  3.  The  anterior  superior  spine  of 
the  ilium.  4.  The  spine  of  the  pubis.  5.  The  pectineal  line  of  the  pubis.  6. 
The  external  cutaneous  nerve.  7.  The  iliacus  muscle.  8.  The  crural  nerve.  9. 
The  psoas  magnus  muscle.  10.  The  crural  branch  of  the  genito-crural  nerve. 
11.  The  femoral  artery.  12.  The  femoral  vein,  receiving  the  internal  saphenous 
vein,  which  pierces  the  sheath  to  open  into  it.  13.  The  external  portion  of  the 
sheath  of  the  femoral  vessels,  lying  in  contact  with  the  artery.  14.  The  large 
funnel-shaped  cavity  in  the  sheath,  to  the  inner  side  of  the  vein,  which  receives 
the  sac  of  femoral  hernia.  15.  The  femoral  ring,  bounded  in  front  by  Poupart's 
ligament,  behind  by  the  pubis,  externally  by  the  femoral  vein,  and  internally 
by  (16)  Gimbernat's  ligament. 

the  femoral  arch.  It  is  formed  by  the  internal  lining  of  the  abdo- 
men ;  and  as  this  has  received  various  names,  according  to  the 
situations  it  may  occupy,  as  transversals  fascia,  iliac  fascia, 
pelvic  fascia,  although  actually  but  one  and  the  same  membrane, 
so  the  sheath  is  said  to  be  formed  in  front  by  the  transversalis 
fascia,  to  the  outer  side  by  the  iliac  fascia,  and  to  the  inner  side 
by  the  pelvic  fascia ;  for  Poupart's  ligament  is  the  line  of  union 
of  these  three  regions  of  the  internal  abdominal  fascia ;  and  in 
escaping  immediately  beneath  Poupart's  ligament  the  vessels 
necessarily  carry  with  them  a  part  of  each. 

The  breadth  of  the  sheath  of  the  vessels  at  Poupart's  ligament 
is  two  inches,  and  in  the  female  more;  but  at  two  inches  below 
the  ligament,  the  sheath  has  diminished  to  three-quarters  of  an 
inch,  and  merges  into  the  common  cellular  covering  of  the  vessels. 

35* 


414 


THE   DISSECTOR. 


Now  it  is  obvious  that  the  artery  and  vein,  placed  side  by  side, 
cannot  occupy  an  area  two  inches  in  breadth,  and  therefore  that 
there  must  be  either  some  other  structure  situated  within  the 
sheath,  or  an  imperfectly  filled  space.  The  latter  is  the  fact ;  for, 
if  we  open  the  sheath,  we  shall  see  a  space,  14,  to  the  inner  side 
of  the  vein,  which  is  only  occupied  by  cellular  tissue,  lymphatic 
vessels,  and  a  lymphatic  gland.  So  that  the  inner  wall  of  the 
sheath  is  separated  by  a  considerable  interval  from  the  vein, 
while  the  outer  wall,  13,  is  in  close  contact,  and  adherent  to  the 
artery  :  moreover,  the  sheath  is  divided  by  septa  into  three  parts, 
one  septum  being  placed  between  the  artery  and  vein,  and  another 
between  the  vein  and  the  space  to  its  inner  side  ;  this  space  being 
the  crural  or  femoral  canal. 

The  lymphatic  gland  is  placed  immediately  under  Poupart's 
ligament,  and  may  be  easily  pushed  into  the  cavity  of  the  abdo- 
men by  using  very  slight  pressure  with  the  finger. 

The  opening,  15  (Fig.  124),  thus  produced  by  the  finger  is  the 
crural  or  femoral  ring:  it  is  bounded  in  front  by  Poupart's  liga- 
ment, 1,  behind  by  the  body  of  the  pubes,  2,  to  the  outer  side  of 
the  femoral  vein,  12,  and  to  the  inner  side  by  Gimbernat's  liga- 
ment, 16.  This  ligament  is  one  insertion  of  Poupart's  ligament, 
which  expands  in  a  radiated  manner  to  be  attached  along  the 
sharp  edge  of  the  pectineal  line. 

Fig.  125. 

A  SECTION  OF  THE  STRUC- 
TURES WHICH  PASS  BENEATH 

THE  FEMORAL  ARCH. — 1.  Pou- 
part's ligament.  2,  2.  The 
iliac  portion  of  the  fascia  lata, 
attached  along  the  margin  of 
the  crest  of  the  ilium,  and  along 
Poupart's  ligament,  as  far  as 
the  spine  of  the  os  pubis  (3) . 
4.  The  pubic  portion  of  the 
fascia  lata,  continuous  at  3 
with  the  iliac  portion,  and 
passing  outwards  behind  the 
sheath  of  the  femoral  vessels 
to  its  outer  border  at  5,  where 
it  divides  into  two  layers  ;  one 
is  continuous  with  the  sheath 
of  the  psoas  (6)  and  iliacus  (7)  ; 
the  other  (8)  is  lost  upon  the 
capsule  of  the  hip-joint  (9). 
10.  The  femoral  nerve,  in- 
closed in  the  sheath  of  the 
psoas  and  iliacus.  11.  Gim- 
bernat's ligament.  12.  The 

femoral  ring,  within  the  femoral  eheath.  13.  The  femoral  vein.  14.  The  fe- 
moral artery  :  the  two  vessels  and  the  ring  are  surrounded  by  the  femoral 
sheath,  and  thin  septa  are  sent  between  the  anterior  and  posterior  wall  of  the 
sheath,  dividing  the  artery  from  the  vein,  and  the  vein  from  the  femoral  ring. 


FEMORAL   HERNIA.  415 

If  the  student,  before  passing  his  finger  through  the  femoral 
from  the  sheath,  should  attempt  to  press  it  from  within  the 
abdomen,  after  tearing  away  the  peritoneum,  he  will  find  an  ob- 
stacle in  a  thin  cellular  membrane  which  is  spread  across  the 
opening  at  its  entrance  :  this  is  the  septum  crurale. 

Now  the  course  which  the  intestine  follows  in  femoral  hernia 
may  be  thus  described.  It  first  descends  through  the  femoral 
ring  into  the  crural  canal,  carrying  with  it  the  peritoneum  and 
septum  crurale.  Secondly,  it  advances  forwards  through  the 
saphenous  opening  in  the  fascia  lata,  this  being  the  weakest  side 
of  the  sheath  of  the  vessels.  In  this  part  of  its  course  it  gains 
two  additional  coverings,  viz  :  the  sheath  of  the  vessels  called 
"fascia  propria,"  and  the  perforated  cellular  tissue  before  de- 
scribed (page  399),  as  forming  the  cribriform  fascia.  Thirdly , 
it  turns  upwards  over  Poupart's  ligament. 

To  return  it  again  to  the  cavity  of  the  abdomen,  we  must  pur- 
sue the  converse  of  the  direction  which  is  followed  in  its  descent, 
».  e.,  we  must  press  it  first  downwards  below  Poupart's  ligament, 
then  backwards  through  the  saphenous  opening,  then  upwards 
through  the  femoral  ring ;  having  previously  flexed  and  rotated 
the  thigh  inwards,  in  order  to  relax  the  structures  concerned  in 
the  hernia. 

But  should  the  intestine  be  strangulated,  that  is,  constricted  in 
its  passage,  so  as  to  arrest  the  progress  of  the  aliment,  and  by  dis- 
tension and  pressure  cause  obstruction  to  the  circulation  of  the 
blood,  and  endanger  the  life  of  the  patient,  we  must  have  recourse 
to  an  operation  for  its  relief.  This  operation  consists  in  dividing 
carefully  all  the  structures  covering  the  hernia,  down  to  the  in- 
testine. The  surgeon  must,  therefore,  know  well  what  parts  are 
likely  to  meet  his  knife  in  the  living  dissection.  Two  of  these 
are  common  to  the  whole  body,  and  must  be  divided  in  every 
operation  ;  the  others  are  peculiar  to  the  region  :  they  are  six 
in  number,  namely  :  integument ;  superficial  fascia ;  cribriform 
fascia ;  fascia  propria  (sheath  of  the  vessels)  ;  septum  crurale  ; 
peritoneal  sac. 

After  opening  the  peritoneal  sac,  the  surgeon  examines  the  in- 
testine and  feels  for  the  stricture.  This  is  generally  the  margin 
of  tha  femoral  ring  ;  or  it  may  be  the  upper  curve  of  the  saphe- 
nous opening  ;  if  the  former,  Gimbernat's  ligament  is  the  proba- 
ble cause  of  the  stricture,  and  should  be  divided  horizontally  ;  if 
the  latter,  the  incision  necessary  for  the  liberation  of  the  intes- 
tine should  be  made  upwards  and  inwards. 

This  is  the  anatomical  principle  of  practice  in  every  case  of 
femoral  hernia ;  and  the  incision  required  for  the  relief  of  the 
stricture  is  very  slight.  But  if  the  operator  be  a  bad  dissector, 
and,  by  a  necessary  consequence,  a  bad  operator,  he  may,  instead 


416  THE   DISSECTOR. 

of  loosening  the  ring,  carry  his  incision  altogether  through  Pou- 
part's  ligament,  or  very  likely  still  further,  and  cut  across  the 
spermatic  or  epigastric  artery,  and  so  complete  the  operation 
with  the  life  of  his  patient. 

Such  an  operator  should  be  forewarned  that  a  variety  in  the 
distribution  of  the  arteries  sometimes  occurs  in  the  vicinity  of 
the  femoral  ring  ;  and  unless  he  be  guarded,  his  reputation  may 
be  forever  destroyed  by  an  unfortunate  complication  of  this  kind. 
The  variety  consists  in  the  origin  of  the  obturator  artery,  from 
the  epigastric  immediately  above  the  femoral  ring.  The  artery 
arising  in  this  situation,  descends  most  frequently  in  contact 
with  the  external  iliac  vein,  and  would  therefore  be  placed  to  the 
outer  side  of  the  hernial  sac,  and  be  comparatively  safe.  But 
sometimes  the  obturator  encircles  the  ring  in  its  course  to  the 
obturator  foramen,  winding  along  near  the  margin  of  Gimber- 
nat's  ligament,  and  would  necessarily  occupy  a  very  dangerous 
position  in  the  operation,  actually  encircling  the  neck  of  the  hernial 
sac,  and  might  be  wounded  by  the  most  skilful  operator.  There- 
fore the  safety  of  the  patient  demands  that  the  surgeon  should 
always  conduct  his  operation  as  if  his  patient  were  the  subject  of 
this  anomalous  distribution,  and  he  may  then  reflect  upon  his 
conduct  even  after  an  unsuccessful  issue  without  self-reproach.1 

GLUTEAL  REGION. 

The  subject  being  turned  on  its  face,  and  a  block  placed  beneath  the 
pubes  to  support  the  pelvis,  the  student  commences  the  dissection  of 
this  region,  by  carrying  an  incision  from  the  apex  of  the  coccyx  along 
the  crest  of  the  ilium  to  its  anterior  superior  spinous  process,  or  vice 
versa,  if  he  be  on  the  left  side.  He  then  makes  an  incision  from  the 
posterior  fifth  of  the  crest  of  the  ilium,  to  the  apex  of  the  trochanter 
major:  this  marks  the  upper  border  of  the  gluteus  niaximus  ;  and  a  third 
incision  from  the  apex  of  the  coccyx  along  the  fleshy  margin  of  the  lower 
border  of  the  gluteus  maximus,  to  the  outer  side  of  the  thigh,  about  four 
inches  below  the  apex  of  the  trochanter  major.  He  then  reflects  the  in- 
tegument, superficial  fascia,  and  deep  fascia,  which  latter  is  very  thin 
over  this  muscle,  from  the  gluteus  maximus,  following  rigidly  the  course 
of  its  fibres ;  and  having  exposed  the  muscle  in  its  entire  extent,  he 
dissects  the  integument  and  superficial  fascia  from  off  the  deep  fascia 
which  binds  down  the  gluteus  medius,  the  other  portion  of  this  region. 
The  more  advanced  student  may  wish  to  dissect  the  cutaneous  nerves  in 
this  region ;  in  which  case  he  removes  only  the  integument,  and  then 
proceeds  to  seek  for  the  nerves  and  follow  them  in  their  course. 


1  The  author  has  met  with  five  or  six  instances  of  this  dangerous  dis- 
tribution in  about  300  bodies,  which  is  a  large  average.  In  a  prepara- 
tion now  before  him,  a  large  branch  of  communication  between  the  epi- 
gastric and  obturator  artery  takes  that  remarkable  course  along  the 
margin  of  Gimbernat's  ligament,  leaving  the  femoral  ring  to  its  outer 
side. 


GLUTEAL   REGION. 


417 


Fig.  126. 


The  CUTANEOUS  NERVES  distributed  to  this  region  are  :  1. 
Branches  of  the  external  cutaneous,  which  turn  back  from  a  little 
below  the  anterior  superior  spine  of  the  ilium.  2.  The  lateral 
cutaneous  branch  of  the  last  dorsal  nerve,  which  crosses  the  crest 
of  the  ilium  just  behind  the  origin  of  the  tensor  vagina?  femoris 
muscle  and  supplies  the  integument  as  low  as  the  trochanter 
major.  3.  The  iliac  branch  of  the  ilio-hypogastric  nerve,  which 
crosses  the  crest  of  the  ilium  a  little  beyond 
its  middle,  and  is  of  small  size.  4.  Two  or 
three  branches,  given  off  by  the  posterior 
division  of  the  lumbar  nerves  ;  these  cross 
the  crest  of  the  ilium  further  back  than  the 
preceding.  5.  Two  or  three  branches  fr«m 
the  posterior  sacral  nerves.  Besides  these, 
the  integument  covering  the  lower  border  of 
the  gluteus  maximus  receives  a  few  cuta- 
neous branches  from  the  lesser  sciatic  nerve. 

The  MUSCLES  of  the  gluteal  region  are — 
Gluteus  maximus, 

medius, 

minimus, 

Pyriformis, 
Gemellus  superior, 
Obturator  internus, 
Gemellus  inferior, 
Obturator  externus, 
Quadratus  femoris. 

The  GLUTEUS  MAXIMUS  (yXovfof,  nates)  is 
the  thick,  fleshy  mass  of  muscle,  of  a  quad- 
rangular shape,  which  forms  the  convexity 
of  the  nates.  In  structure,  it  is  extremely 
coarse,  being  made  up  of  large  fibres,  which 
are  collected  into  fasciculi,  and  these  again 
into  distinct  muscular  masses,  separated  by 
deep  cellular  furrows.  It  arises  from  the 
posterior  fifth  of  the  crest  of  the  ilium,  from 
the  posterior  surface  of  the  sacrum  and 

THE  MUSCLES  OF  THE  POSTERIOR  FEMORAL  AND  GLUTEAL  REGION. — 1.  The 
glutens  medius.  2.  The  glutens  maximus.  3.  The  vastus  externus  covered  in 
by  fascia  lata.  4.  The  long  head  of  the  biceps.  5.  Its  short  head.  6.  The 
semi-tendinosus.  7.  The  semi-membranosug.  8.  The  gracilis.  9.  A  part  of 
the  inner  border  of  the  adductor  magnus.  10.  The  edge  of  the  sartorius. 
H.  The  popliteal  space.  12.  The  gastrocnemius  muscle  ;  its  two  heads.  The 
tendon  of  the  biceps  forms  the  outer  hamstring  :  and  the  sartorius  with  the 
tendons  of  the  gracilis,  semi-tendinosus,  and  eeini-merubranosus,  the  inner 
hamstring. 


418  THE  DISSECTOR. 

coccyx,  and  from  the  great  sacro-ischiatic  ligament.  It  passes 
obliquely  outwards  and  downwards,  to  be  inserted  into  the  rough 
line  leading  from  the  trochanter  major  to  the  liriea  aspera,  and  is 
continuous  by  means  of  its  tendon  with  the  fascia  lata  covering 
the  outer  side  of  the  thigh.  Several  bursse  are  situated  between 
this  muscle  and  subjacent  parts  ;  one  upon  the  tuberosity  of  the 
ischium,  one  between  its  tendon  and  the  trochanter  major,  and 
one  between  it  and  the  tendon  of  the  vastus  externus. 

After  this  muscle  lias  been  sufficiently  studied,  it  must  be  turned 
down  from  its  origin.  Its  dissection,  however,  from  the  parts  beneath 
demands  considerable  care,  as  a  number  of  arteries  and  nerves  are  situated 
immediately  below  it. 

The  GLUTEUS  MEDIUS  is  placed  in  front  of  rather  than  beneath 
the  gluteus  maximus,  and  is  covered  in  by  a  process  of  the  deep 
fascia,  which  is  very  thick  and  dense.  It  arises  from  the  outer 
lip  of  the  crest  of  the  ilium  for  four-fifths  of  its  length,  from  the 
surface  of  bone  between  that  border,  and  the  superior  curved  line 
on  the  dorsum  ilii,  and  from  the  dense  fascia  above  mentioned. 
Its  fibres  converge  to  the  outer  part  of  the  trochanter  major,  into 
which  its  tendon  is  inserted. 

This  muscle  should  now  be  removed  from  its  origin  and  turned  down, 
so  as  to  expose  the  next  which  is  situated  beneath  it ;  a  bursa  will  be 
found  between  its  tendon  and  the  trochanter. 

The  GLUTEUS  MINIMUS  (Fig.  128,  i)  is  a  radiated  muscle,  aris- 
ing from  the  surface  of  the  dorsum  ilii,  between  the  superior  and 
inferior  curved  lines :  its  fibres  converge  to  the  anterior  border 
of  the  trochanter  major,  into  which  it  is  inserted  by  means  of  a 
rounded  tendon.  There  is  no  distinct  separation  between  the 
gluteus  medius  and  minimus  anteriorly. 

The  gluteus  minimus  should  be  divided  through  its  tendon  and  turned 
upwards  in  order  to  show  that  head  of  the  rectus  muscle  which  proceeds 
from  the  upper  lip  of  the  acetabulum. 

To  understand  the  exact  relations  and  origins  of  the  next  muscles, 
the  student  should  consult  his  skeleton.  Upon  the  posterior  and  lateral 
aspect  of  the  pelvis,  he  will  find  a  considerable  vacuity.  This  is  broken 
in  upon  by  a  sharp  spinous  process  projected  from  the  border  of  the 
ischium,  the  spine  of  the  ischium :  the  excavated  sweep  immediately 
above  this  spine  is  called  the  great  sacro-ischiatic  notch,  in  contradis- 
tinction to  another  sweep  beneath  the  spine,  named  the  lesser  sacro- 
ischiatic  notch ;  and  the  lesser  sacro-ischiatic  notch  is  bounded  inferiorly 
by  a  thick  tubercle,  the  tuberosity  of  the  ischium.  In  the  subject,  the 
narrow  extremity  of  a  radiate  ligament  is  attached  to  the  spine  of  the 
ischium,  while  its  expanded  end  is  connected  to  the  side  of  the  sacrum 
and  coccyx  :  hence  it  is  named  sacro-ischiatic,  and  is  further  known  by 
the  cognomina,  lesser  and  anterior,  which  serve  to  distinguish  it  from 
another  ligament,  radiated  at  each  extremity,  attached  by  the  broader 
end  to  the  posterior  spinous  process  of  the  ilium,  the  side  of  the  sacrum 
and  coccyx,  and  by  its  smaller  end  to  the  inner  border  of  the  tuberosity 
of  the  ischium.  This  ligament  is  necessarily  longer  than  the  former, 


SACRO-ISCHIATIC  OPENINGS. 


419 


and  more  posterior  :  hence  it  is  named  the  posterior  or  great  sacro-ischia- 
tic  ligament.  These  two  ligaments  convert  the  notches  into  foramina, 
which  are  thence  called  the  superior  or  great  sacro-ischiatic  foramen,  and 
the  inferior  or  lessor  sacro-ischiatic  foramen.  Let  us  now  return  to  the 
muscles. 

The  PYRIFORMIS  muscle  (Fig.  128,  3,  pyrum,  a  pear,  t.  e.  pear- 
shaped)  arises  from  the  anterior  surface  of  the  sacrum,  by  little 
slips   interposed  between   the 
anterior  sacral  foramina  from  Fig.  127. 

the  first  to  the  fourth.  It  passes 
out  of  the  pelvis,  through  the 
great  sacro-ischiatic  foramen, 
and  is  insertedby  a  rounded  ten- 
don into  the  posterior  border 
of  the  trochanter  major. 

Immediately  below  the  pyri- 
formis  is  a  small  slip  of  muscle, 
the  GEMELLUS  SUPERIOR  (gemel- 
lus,  double,  twin)  :  it  arises 
from  the  spine  of  the  ischium, 
and  is  inserted  into  the  upper 
border  of  the  tendon  of  the 
obturator  interims,  and  into 
the  digital  fossa  of  the  trochan- 
ter major. 

The     OBTURATOR     INTERNUS 

arises  from  the  inner  surface  of 

the  anterior  wall  of  the  pelvis, 

being  attached  to  the  margin 

of  bone  around  the  obturator 

foramen,  and  to  the  obturator 

membrane.     It  passes  out  of 

the  pelvis  through  the  lesser 

sacro-ischiatic  foramen,  and  is 

inserted  by  a  flattened  tendon 

into  the  digital  fossa  of  the 

trochanter  major.     The  lesser 

sacro-ischiatic      notch,      over 

which    this    muscle    plays    as 

through  a  pulley,  is  faced  with 

cartilage,  and  provided  with  a 

synovial  bursa  to  facilitate  its 

movements.      The   tendon   of 

the  obturator  is  supported  on 

each  side  by  the  gemelli  muscles  (hence  their  names),  which  are 

inserted  into  the  sides  of  the  tendon,  and  appear  to  be  auxiliaries 

or  superadded  portions  of  the  obturator  internus. 


THE  DEEP  MUSCLES  OP  THE  GLTT- 
TEAL  REGION. — 1.  The  external  sur- 
face of  the  ilium.  2.  The  posterior 
surface  of  the  sacrum.  3.  The  pos- 
terior sacro-iliac  ligaments.  4.  The 
tuberosity  of  the  ischium.  5.  The 
great  or  posterior  sacro-ischiatic  liga- 
ment. 6.  The  lessor  or  anterior  sacro- 
ischiatic  ligament.  7.  The  trochanter 
major.  8.  The  gluteus  minimus.  9. 
The  pyriformis.  10.  The  gemellus 
superior.  11.  The  obturator  in  tern  us 
muscle,  passing  out  of  the  lessor  sacro- 
ischiatio  foramen.  12.  The  gemellna 
inferior.  13.  The  quadratus  femoris. 
14.  The  upper  part  of  the  adductor 
magnns.  15.  The  vastus  externus. 
16.  The  biceps.  17.  The  gracilis.  18. 
The  semi-tendinosus. 


420  THE   DISSECTOR. 

The  GEMELLUS  INFERIOR  arises  from  the  posterior  point  of  the 
tuberosity  of  the  ischium,  and  is  inserted  into  the  lower  border 
of  the  tendon  of  the  obturator  internus,  and  into  the  digital 
fossa  of  the  trochanter  major. 

Placed  deeply  between  the  gemellus  inferior  and  the  quadra- 
tus  femoris,  may  be  seen  the  tendon  of  the  obturator  externus, 
becoming  more  superficial  as  it  passes  outwards  to  its  "insertion 
into  the  digital  fossa  of  the  trochanter  major :  it  arises  from  the 
external  surface  of  the  obturator  ligament,  and  from  the  margin 
of  bone  immediately  surrounding  it.  (Page  403.) 

The  QUADRATUS  FEMORIS  (Fig.  128,  5),  square-shaped,  arises 
from  the  external  border  of  the  tuberosity  of  the  ischium,  and  is 
inserted  into  a  rough  line  on  the  posterior  border  of  the  tro- 
chanter major,  which  is  thence  named  linea  quadrati. 

ACTIONS. — The  glutei  muscles  are  abductors  of  the  thigh,  when  they 
take  their  fixed  point  from  the  pelvis.  Taking  their  fixed  point  from  the 
thigh,  they  steady  the  pelvis  on  the  head  of  the  femur ;  this  action  is 
peculiarly  obvious  in  standing  on  one  leg  ;  they  assist  also  in  carrying 
the  leg  forward,  in  progression.  The  gluteus  minimus  being  attached  to 
the  anterior  border  of  the  trochanter  major,  rotates  the  limb  slightly  in- 
wards. The  gluteus  medius  and  maximus,  from  their  insertion  into  the 
posterior  aspect  of  the  bone,  rotate  the  limb  outwards  :  the  latter  is, 
moreover,  a  tensor  of  the  fascia  of  the  thigh.  The  other  muscles  rotate 
the  limb  outwards,  everting  the  knee  and  foot ;  hence  they  are  named 
external  rotators. 

Vessels  and  Nerves  of  the  Gluteal  Region. 

Arteries.  Nerves. 

f  Superficial  branch.  .  f  Superior  branch. 

Gluteal  \  Deep  superior  branch.  Gluteal     ^     branch> 

(.  Deep  inferior  branch. 


Ischi"     '  ^ -'  ischiatici. 


I       internal. 

Great  ischiatic. 
Internal  pudic.  Internal  pudic. 

The  gluteal  artery  and  nerve  (Fig.  128,  11)  are  found  imme- 
diately above  the  pyriformis  muscle  ;  the  other  vessels  and  nerves, 
12,  14,  immediately  beneath  that  muscle. 

The  GLUTEAL  ARTERY  is  the  continuation  of  the  posterior  trunk 
of  the  internal  iliac  ;  it  passes  out  of  the  pelvis  through  the  great 
sacro-ischiatic  foramen,  above  the  pyriformis  muscle,  and  divides 
into  three  branches ;  superficial,  deep  superior,  and  deep  inferior. 

The  superficial  branch  passes  backwards  between  the  gluteus 
maximus  and  medius,  and  is  distributed  to  the  gluteus  maximus 
and  to  the  integument  of  the  gluteal  and  sacral  region. 

The  deep  superior  branch  passes  forwards  along  the  superior 
curved  line  of  the  ilium,  between  the  gluteus  medius  and  minimus  to 
the  anterior  superior  spinous  process  of  the  ilium  where  it  inoscu- 


VESSELS   OF   GLUTEAL   REGION. 


421 


Fig.  128. 


lates  with  the  superficial  circumflexa  ilii  and  external  circumflex. 
There  are  frequently  two  arteries  occupying  the  place  of  this  branch. 

The  deep  inferior  branches,  two  or  three  in  number,  cross  the 
gluteus  minimus  obliquely  to  the  trochanter  major,  where  they 
inosculate  with  branches  of  the  external  circumflex  and  ischiatic 
arteries,  and  send  branches  through  the  muscle  for  the  supply  of 
the  hip-joint. 

The  arteries  in  this  region  are  all  branches  of  the  internal  iliac  within 
the  pelvis,  and  the  nerves  are  derived  from  the  sacral  plexus ;  hence, 
a  part  of  their  course  cannot,  at  present,  be  seen.  They  all  quit  the 
pelvis  through  the  great  sacro-ischiatic  foramen. 

The  ISCHIATIC  ARTERY,  one  of  the  terminal  branches  of  the  ante- 
rior trunk  of  the  internal  iliac,  escapes  from  the  pelvis  beneath 
the  pyriformis  muscle,  and  passing 
downwards  with  the  ischiatic  nerves, 
in  the  interval  between  the  tuberosity 
of  the  ischium  andthe  trochanter  major, 
divides  into  several  branches,  the  prin- 
cipal of  which  are  the  coccygeal,  comes 
nervi  ischiatici  and  muscular. 

The  coccygeal  branch  pierces  the 
great  sacro-ischiatic  ligament,  and  is 
distributed  to  the  coccygeus  and  leva- 
tor  ani  muscles,  and  to  the  integument 
of  the  anal  and  coccygeal  region. 

The  comes  nervi  ischiatici  is  a  slender 
branch  which  accompanies  the  great 
ischiatic  nerve,  extending  as  far  as  the 
lower  part  of  the  thigh. 

The  muscular  branches  supply  the 
muscles  of  the  posterior  part  of  the  hip 
and  thigh,  and  send  twigs  to  the  hip- 
joint.  They'  inosculate  with  the  inter- 
nal and  external  circumflex  arteries, 
obturator,  and  superior  perforating. 

A  DEEP  POSTERIOR  VIEW  OF  THE  ANATOMY  OF  THE  HlP  J  SHOWING  THE  MuS- 
CLES,  VESSELS,  AND  NERVES,  WHICH  ARE  EXPOSED  BY  THE  REMOVAL  OF  THB 
GLUTEUS  MAXIMUS  MUSCLE. — 1.  The  gluteus  minimus  muscle.  2.  The  tro- 
chanter major  of  the  femur.  3.  The  pyriformis  muscle.  4.  The  tendon  of  the 
obturator  internus  muscle,  bounded  above  by  the  gemellns  superior,  and  below 
by  the  gemellus  inferior.  5.  The  quadratus  femoris  muscle.  6.  The  adductor 
ni.i^nus.  7.  The  vastus  externus  muscle.  8.  The  long  head  of  the  biceps.  9. 
The  serai-tendinosus.  10.  The  gracilis.  11.  The  gluteal  artery  and  nerve, 
escaping  from  the  pelvis  above  the  pyriformis  muscle.  12.  The  great  ischiatic 
nerve.  13.  The  lesser  ischiatic  nerve,  and  between  the  two  the  ischiatic  artery. 
14.  The  pudic  artery  and  nerve.  All  these  vessels  and  nerves  pass  out  from  the 
pelvis  below  the  pyriformis  muscle.  15.  The  great  or  posterior  sacro-ischiatic 
ligament.  *  The  tuberosity  of  the  ischium.  16.  Tho  posterior  branches  of  the 
sacral  nerves. 
36 


422  THE  DISSECTOR. 

The  INTERNAL  PUBIC  ARTERY,  the  other  terminal  branch  of  the 
anterior  trunk  of  the  internal  iliac,  also  issues  from  the  pelvis 
through  the  great  ischiatic  foramen  below  the  pyriformis  to  dis- 
appear immediately  beneath  the  great  sacro-ischiatic  ligament, 
and  pursue  its  course  within  the  pelvis. 

From  the  description  usually  given  of  this  artery,  the  student 
might  imagine  that  its  course  was  extremely  eccentric,  going  out 
of  the  pelvis  and  then  going  in.  But  if  he  refer  to  his  skeleton 
and  to  the  subject,  he  will  see  that  the  artery  forms  the  most 
gentle  curve  imaginable  in  this  part  of  its  course ;  and  that  its 
various  relation  to  the  pelvis  depends  upon  the  projection  inwards 
of  the  spine  of  the  ischium,  upon  which  the  artery,  with  its  veins 
and  nerve,  rests  in  this  region. 

Upon  entering  the  lesser  ischiatic  foramen,  the  internal  pudic 
artery  crosses  the  lower  part  of  the  obturator  internus  muscle  to 
the  ramus  of  the  ischium,  along  which,  and  the  ramus  of  the 
pubes,  it  ascends  to  the  symphysis.  Its  branches  are  distributed 
to  the  perineum. 

The  VEINS,  as  in  all  the  secondary  arteries  of  the  body,  are 
placed  by  the  side  of  the  arteries  in  pairs,  which  are  called 
"vence  comites." 

Nerves  of  the  Gluteal  Region. 

The  GLUTEAL  NERVE  (superior  gluteal;  Fig.  128,  n  ;  Fig.  132, 
2)  is  a  branch  of  the  lumbo-sacral  or  fifth  lumbar  nerve.  It  passes 
out  of  the  pelvis  with  the  gluteal  artery  through  the  great  sacro- 
ischiatic  foramen,  and  divides  into  a  superior  and  inferior  branch. 

The  superior  branch  follows  the  direction  of  the  superior  curved 
line  of  the  ilium,  accompanying  the  deep  superior  branch  of  the 
gluteal  artery,  and  sends  filaments  to  the  gluteus  medius  and 
minimus. 

The  inferior  branch  passes  obliquely  downwards  and  forwards 
between  the  gluteus  medius  and  minimus  to  the  tensor  vaginae 
femoris,  and  is  distributed  to  all  the  three  muscles. 

The  LESSER  ISCHIATIC  NERVE  (Fig.  128,  is;  Fig.  132,  G),  one  of 
the  branches  of  the  sacral  plexus,  passes  out  of  the  pelvis  through 
the  great  sacro-ischiatic  foramen  below  the  pyriformis  muscle, 
and  continues  its  course  downwards  through  the  middle  of  the 
thigh  to  the  lower  part  of  the  popliteal  region,  where  it  pierces 
the  fascia  and  becomes  subcutaneous.  It  then  associates  itself 
with  the  external  saphenous  vein,  and  descends  to  the  lower  part 
of  the  leg  communicating  with  the  external  saphenons  nerve. 
The  branches  of  the  lesser  ischiatic  nerve  are  muscular  and  cuta- 
neous. 

The  muscular  or  inferior  gluteal  are  several  large  branches 
distributed  to  the  gluteus  maximus. 


POSTERIOR  FEMORAL  REGION.  423 

The  cutaneous  branches  are  divisible  into  external,  internal,  and 
middle.  The  external  cutaneous  branches  are  several  filaments 
which  turn  around  the  lower  border  of  the  gluteus  maximus,  and 
are  distributed  to  the  integument  over  the  hip  and  outer  side  of 
the  thigh.  The  internal  cutaneous  branches  are  distributed 
to  the  integument  of  the  upper  and  inner  part  of  the  thigh. 
One  of  these  branches,  larger  than  the  rest,  inferior  pudendal, 
curves  around  the  tuberosity  of  the  ischium,  pierces  the  fascia 
lata  near  the  ramus  of  that  bone,  and,  after  communicating  with 
the  superficial  perineal  nerve,  is  distributed  to  the  integument  of 
the  scrotum  and  penis.  The  middle  cutaneous  branches,  two  or 
three  in  number,  are  derived  from  the  lesser  ischiatic  in  its  course 
down  the  thigh  and  are  distributed  to  the  integument. 

The  GREAT  ISCHIATIC  NERVE  (Fig.  128,  12;  Fig.  132,  ,7)  is  the 
largest  nervous  cord  in  the  body ;  it  is  formed  by  the  sacral 
plexus,  or  rather  is  a  prolongation  of  the  plexus  ;  and  at  its  exit 
from  the  great  sacro-ischiatic  foramen,  beneath  the  pyriformis, 
measures  three  quarters  of  an  inch  in  breadth.  It  descends 
through  the  middle  of  the  space  between  the  trochanter  major 
and  tuberosity  of  the  ischium,  and  along  the  posterior  part  of  the 
thigh  to  its  lower  third,  where  it  divides  into  two  large  terminal 
branches,  internal  and  external  popliteal.  This  division  some- 
times takes  place  at  the  plexus,  and  the  two  nerves  descend  side  by 
side ;  sometimes  one  passes  out  of  the  pelvis  above  the  pyriformis, 
or  even  pierces  that  muscle.  In  its  course  downwards  the  nerve 
rests  on  the  gemellus  superior,  tendon  of  the  obturator  internus, 
gemellus  inferior,  quadratus  femoris,  and  then  gets  between  the 
flexor  muscles  and  abductor  magnus;  a  few  muscular  twigs  are 
given  off  by  the  nerve  while  in  the  gluteal  region. 

The  INTERNAL  PUBIC  NERVE  (Fig.  128,  i4j  Fig.  132,  5)  may  be 
seen  lying  by  the  side  of  the  internal  pudic  artery.  It  proceeds 
from  the  lower  part  of  the  sacral  plexus,  and  passing  out  of  the 
pelvis  through  the  great  sacro-ischiatic  foramen  below  the  pyri- 
formis muscle,  enters  it  again  through  the  lesser  sacro-ischiatic 
foramen,  and  accompanies  the  internal  pudic  artery  in  its  course. 

POSTERIOR  FEMORAL  REGION. 

Carry  an  incision  along  the  middle  of  the  posterior  aspect  of  the 
thigh,  as  far  as  the  bend  of  the  knee.  Bound  it  in  this  situation  by  a 
transverse  incision,  and  reflect  the  integument  to  either  side.  In  the  su- 
perficial fascia  will  be  seen  the  cutaneous  branches  of  the  lesser  ischiatio 
nerve. 

Upon  removing  the  superficial  fascia,  the  deep  fascia  will  be 
found  to  be  extremely  thin  ;  and,  on  turning  it  aside,  we  bring 
into  view  the  three  muscles  of  this  region,  the  flexors  of  the 
leg- 


424  THE   DISSECTOR. 

Biceps. 

Semi-tendinosus. 

Semi-membranosus. 

The  BICEPS  FLEXOR  CRURIS  (bis,  double — xt^a^,  head)  arises 
by  two  heads,  one  by  a  common  tendon  with  the  semi-tendinosus 
from  the  upper  and  back  part  of  the  tuberosity  of  the  ischium ; 
the  other,  muscular,  and  much  shorter,  from  the  lower  two-thirds 
of  the  external  border  of  the  linea  aspera.  This  muscle  forms 
the  outer  hamstring,  and  is  inserted  by  a  strong  tendon  into  the 
head  of  the  fibula  ;  a  portion  of  the  tendon  being  continued  into 
the  fascia  of  the  leg. 

The  SEMI-TENDINOSUS,  remarkable  for  its  long  tendon,  arises 
in  common  with  the  long  head  of  the  biceps  from  the  upper  and 
back  part  of  the  tuberosity  of  the  ischium.  It  is  inserted  into 
the  inner  tuberosity  of  the  tibia;  and  sends  an  expansion  to  the 
fascia  of  the  leg. 

These  two  muscles  must  be  dissected  from  the  tuberosity  of  the  ischium 
to  bring  into  view  the  origin  of  the  next. 

The  SEMI-MEMBRANOSUS,  remarkable  for  the  tendinous  expan- 
sion upon  its  anterior  and  posterior  surfaces,  arises  from  the  tube- 
rosity of  the  ischium,  in  front  of  the  common  origin  of  the  two 
preceding  muscles.  It  is  inserted  into  the  posterior  part  of  the 
inner  tuberosity  of  the  tibia;  at  its  insertion,  the  tendon  splits 
into  three  portions,  one  of  which  is  inserted  in  a  groove  on  the 
inner  side  of  the  head  of  the  tibia,  beneath  the  internal  lateral 
ligament.  The  second  is  continuous,  with  an  aponeurotic  ex- 
pansion which  binds  down  the  popliteus  muscle,  the  popliteal 
fascia  ;  and  the  third  turns  upwards  and  outwards  to  the  ex- 
ternal condyle  of  the  femur,  forming  the  middle  portion  of  the 
posterior  ligament  of  the  knee-joint  (ligamentum  posticum 
Winslowii). 

The  tendons  of  the  two  last  muscles,  viz :  the  semi-tendinosus 
and  semi-membranosus,  with  those  of  the  gracilis  and  sartorius, 
form  the  inner  hamstring. 

If  the  semi-membranosus  muscle  be  turned  down  from  its  origin,  the 
student  will  bring  into  view  the  broad  and  radiated  expanse  of  the  ad- 
ductor magnus,  upon  which  the  great  ischiatic  nerve  and  the  three  flexor 
muscles  above  described  rest. 

ACTIONS. — These  three  hamstring  muscles  are  the  direct  flexors  of  the 
leg  upon  the  thigh ;  and,  by  taking  their  origin  from  below,  they  balance 
the  pelvis  on  the  lower  extremities. 

Arteries  and  Nerves  of  the  Posterior  Femoral  Region. 

The  ARTERIES  of  this  region  are  the  external  and  internal  cir- 
cumflex, three  perforating,  the  termination  of  the  profunda  ferno- 
ris  and  the  popliteal. 


POPLITEAL  REGION.  425 

The  middle  branch  of  the  external  circumflex  is  seen  piercing 
the  upper  part  of  the  vastus  externus,  to  inosculate  with  the  in- 
ternal circumflex,  ischiatic,  and  superior  perforating  artery. 
The  internal  circumflex  makes  its  appearance  between  the  upper 
border  of  the  adductor  magnus,  and  the  lower  border  of  the 
quadratus  femoris.  It  inosculates  with  the  external  circumflex, 
ischiatic,  and  superior  perforating  artery. 

The  three  perforating  arteries  emerge  on  the  posterior  aspect 
of  the  thigh,  by  passing  through  tendinous  arches  between  the 
adductor  magnus  and  the  linea  aspera.  They  anastomose  with 
each  other,  with  the  circumflex  and  ischiatic  arteries  above,  and 
with  the  articular  branches  of  the  popliteal  below.  The  pro- 
funda  artery  passes  through  the  adductor  magnus,  close  to  the 
linea  aspera,  and  is  protected  from  pressure  by  a  tendinous  arch, 
thrown  across  the  bone.  It  makes  its  appearance  at  about  an 
inch  above  the  commencement  of  the  popliteal  artery. 

The  NERVES  in  this  region  are  the  greater  and  lesser  ischiatic. 
The  continuation  of  the  lesser  ischiatic  is  seen  upon  the  semi- 
tendinosus  muscle. 

The  great  ischiatic  nerve  (Fig.  132,  7)  runs  down  the  middle  of 
the  posterior  femoral  region,  being  situated  between  the  flexor 
muscles  and  the  adductor  magnus.  At  the  lower  third  of  the 
thigh  it  divides  into  two  nerves  of  nearly  equal  size,  the  internal 
popliteal,  9,  and  external  popliteal,  8.  Its  branches  are  muscular 
and  articular.  The  muscular  branches  are  distributed  to  the 
biceps,  semi-tendiriosus,  semi-merabranosus  and  adductor  magnus. 
The  articular  branch  descends  to  the  external  condyle  of  the 
femur  and  is  distributed  to  the  knee-joint. 

POPLITEAL  REGION. 

The  lower  part  of  the  posterior  femoral  region  is  a  surgical 
region  of  some  importance,  the  popliteal  (Fig.  129).  It  is  a  dia- 
mond-shaped space,  bounded  above  on  each  side  by  the  two  ham- 
strings 1,  2r  and  below  by  the  two  heads,  3,  3,  of  the  great 
muscle  of  the  calf,  the  gastrocnemius.  On  dissecting  back  the 
integument,  a  large  vein,  8,  which  runs  up  the  middle  of  the 
posterior  part  of  the  leg,  the  external  saphenous,  is  seen  between 
the  layers  of  the  superficial  fascia.  To  this  several  cutaneous 
veins  converge,  which  must  be  divided  in  making  an  incision  for 
the  purpose  of  reaching  the  artery.  If  the  superficial  fascia  be 
dissected  away,  the  external  saphenous  vein  will  be  seen  passing 
through  an  oval  foramen  in  the  deep  popliteal  fascia,  to  termi- 
nate in  the  popliteal  vein.  Some  cutaneous  branches  of  nerves 
from  the  lesser  ischiatic  and  internal  cutaneous  of  the  anterior 
crural  may  also  be  found  in  the  superficial  fascia. 

36* 


426 


THE   DISSECTOR. 


Fig.  129. 


The  deep  popliteal  fascia  is  thin,  and  will  be  removed  without 
being  observed,  unless  the  dissector  proceed  cautiously.  It  is  a 
part  of  the  common  deep  fascia  (fascia  lata)  investing  the  entire 
limb.  Beneath  the  deep  fascia  is  a  quantity  of  adipose  substance 
which  fills  up  the  whole  popliteal  space,  from  the  bone  and  joint 
to  the  surface,  and  protects  and  supports  the  popliteal  vessels 
and  nerves. 

It  will  be  recollected,  that  at  the  upper  part  of  this  popliteal 
space  the  great  ischiatic  nerve  divides  into  two  branches  of  nearly 
equal  size,  the  internal  and  external  popliteal.  The  internal 
popliteal,  4,  runs  along  the  middle  line  of 
this  space,  from  apex  to  apex  of  its  diamond- 
shaped  area.  It  is  placed  near  the  surface, 
and  is  easily  found  on  slightly  separating  the 
adipose  tissue.  This  nerve  divides  the  region 
into  two  equal  halves  :  in  the  external  one 
will  be  found  a  large  branch  of  the  internal 
popliteal,  the  external  saphenous  nerve,  and 
the  external  popliteal  nerve,  6,  lying  along 
the  tendon  of  the  biceps  muscle. 

To  the  inner  side  of  the  internal  popliteal 
nerve,  at  a  variable  depth,  is  the  popliteal  vein, 
to  which  the  external  saphenous  vein  will 
serve  as  a  guide,  and  to  the  inner  side  of  the 
vein,  and  still  deeper,  resting  on  the  femur, 
is  the  popliteal  artery. 

If  therefore  it  were  necessary  to  place  a  ligature 
around  the  popliteal  artery,  we  should  make  a 
longitudinal  incision  along  the  middle  of  the  pop- 
liteal space,  which  should  divide  the  integument, 
the  superficial  fascia,  remembering  the  external 
saphenous  vein,  the  deep  fascia,  then  cautiously 
make  our  way  through  the  adipose  substance,  a 
little  to  the  inner  side  of  the  middle  line,  down  to 
the  artery,  and  hook  around  it  the  aneurismal 
needle. 

In  the  upper  part  of  the  popliteal  space,  the 
artery  lies  comparatively  superficially;  and  is 
altogether  to  the  inner  side  of  the  internal  pop- 
liteal nerve.  In  the  middle  portion  it  is  deepest : 

THE  POPLITEAL  REGION,  AND  THE  SUPERFICIAL  ANATOMY  OF  THE  CALF  OF 
THE  LEG. — 1.  The  inner  hamstring.  2.  The  outer  hamstring.  3,  3.  The  two 
heads  of  the  gastrocnemius  muscle.  4.  The  popliteal  artery,  vein,  and  nerve, 
in  their  relative  position  from  within  outwards ;  the  artery  being  the  deepest, 
next  the  vein,  and  the  nerve  quite  superficial.  5.  The  termination  of  the  is- 
chiatic nerve  dividing  into  the  internal  popliteal  nerve,  and  6,  the  peroneal  or 
external  popliteal.  7.  The  external  saphenous  nerve,  formed  by  the  union  of 
the  communicans  peronei,  from  the  peroneal,  and  communicans  poplitei  from 
the  popliteal  nerve.  8.  The  external  saphenous  vein.  9.  The  outer  harder  of 
the  soleus  muscle.  10.  The  tendo  Achillis. 


POPLITEAL  ARTERY.  42f 

and  between  the  heads  of  the  gastrocnemius,  it  again  becomes  superficial, 
but  is  crossed  by  numerous  muscular  branches,  both  of  the  artery  and 
nerve,  which  would  interfere  with  the  progress  of  an  operation. 

The  floor  of  the  popliteal  space  is  formed  by  the  expanded 
inferior  extremity  of  the  femur,  by  the  knee-joint,  and  by  the 
popliteal  muscle  immediately  below  the  joint. 

The  POPLITEAL  ARTERY  (Fig.  129,  4)  runs  obliquely  out- 
wards, through  the  middle  of  the  popliteal  space,  from  the 
opening  in  the  abductor  magnus,  to  the  lower  border  of  the  pop- 
liteus  muscle,  where  it  divides  into  the  anterior  and  posterior 
tibial  artery. 

In  this  course  it  rests  first  on  the  femur,  then  on  the  posterior 
ligament  of  the  knee-joint,  then  on  the  fascia  covering  the  pop- 
liteal muscle :  superficial  and  external  to  it  is  the  popliteal  vein, 
and  still  more  superficial  and  external,  the  internal  popliteal 
nerve.  It  has,  also,  in  relation  with  it,  four  or  five  lymphatic 
glands  which  lie  near  its  cylinder. 

The  branches  of  the  popliteal  artery  are,  the — 
Superior  external  articular, 
Superior  internal  articular, 
Azygos  articular, 
Inferior  external  articular, 
Inferior  internal  articular, 
SuraJ. 

The  superior  articular  arteries,  external  and  internal,  wind 
around  the  femur  immediately  above  the  condyles,  to  the  front  of 
the  knee-joint,  anastomosing  with  each  other,  with  the  external 
circumflex,  the  anastomotica  magna,  the  inferior  articular  and 
the  recurrent  of  the  anterior  tibial.  The  external  passes  beneath 
the  tendon  of  the  biceps,  and  the  internal  through  an  arched 
opening  beneath  the  tendon  of  the  adductor  magnus.  They  sup- 
ply the  knee-joint  and  lower  part  of  the  femur,  and  give  branches 
to  the  vasti  muscles. 

The  azygos  articular  artery  pierces  the  posterior  ligament  of 
the  joint,  the  ligamentum  posticum  Winslowii,  and  supplies  the 
crucial  ligaments  and  synovial  membrane. 

The  inferior  articular  arteries  wind  around  the  head  of  the 
tibia,  immediately  below  the  joint,  and  anastomose  with  each 
other,  the  superior  articular  arteries,  and  the  recurrent  of  the 
anterior  tibial.  The  external  passes  beneath  the  two  external 
lateral  ligaments  of  the  joint,  and  the  internal  beneath  the  inter- 
nal lateral  ligament. 

The  sural  arteries  (sura,  the  calf)  are  two  muscular  branches 
of  large  size,  distributed  to  the  two  heads  of  the  gastrocnemius 
muscle.  Other  muscular  branches  are  given  off  from  the  upper 
part  of  the  popliteal  to  supply  the  hamstring  muscles. 


428  THE   DISSECTOR. 

The  INTERNAL  POPLITEAL  NERVE  (Fig.  129, 4 ;  Fig.  132,  9)  runs 
through  the  middle  of  the  popliteal  space,  from  the  division  of 
the  great  ischiatic  nerve  to  the  lower  border  of  the  popliteus 
muscle,  where  it  passes  with  the  artery  beneath  the  arch  of  the 
soleus,  and  becomes  the  posterior  tibial  nerve.  It  is  superficial 
in  the  whole  of  its  course,  and  lies  externally  to  the  vein  and 
artery. 

The  branches  of  the  internal  popliteal  nerve  are,  muscular  or 
sural,  articular,  and  a  cutaneous  branch — the  external  saphenous 
nerve. 

The  muscular  branches,  of  considerable  size,  and  four  or  five 
in  number,  are  distributed  to  the  gastrocnenrius,  soleus,  plantaris, 
and  popliteus  muscles. 

The  articular  branches,  two  or  three  in  number,  supply  the 
knee-joint;  two  of  the  twigs  accompanying  the  internal  articular 
arteries. 

The  external  or  short  saphenous  nerve  (communicans  poplitei, 
vel  tibialis)  proceeds  from  the  middle  of  the  internal  popliteal, 
and  descends  in  the  groove  between  the  two  bellies  of  the  gas- 
trocnemius muscle  to  the  middle  of  the  leg;  it  then  pierces  the 
fascia,  and,  after  receiving  the  communicans  peronei,  comes  into 
relation  with  the  external  saphenous  vein,  and  follows  the  course 
of  that  vein  to  the  outer  ankle,  to  which  and  to  the  integument 
of  the  heel  and  foot  it  distributes  branches. 

The  EXTERNAL  POPLITEAL  NERVE  (peroneal,  Fig.  129,  e ;  Fig. 
132,  s),  one-half  smaller  than  the  internal,  passes  downwards  by 
the  side  of  the  tendon  of  the  biceps,  and  crosses  the  internal  head 
of  the  gastrocnemius  and  the  head  of  the  soleus  to  the  neck  of  the 
fibula;  it  then  pierces  the  peroneus  longus  muscle  and  divides 
into  two  branches,  anterior  tibial  and  musculo-cutaneous. 

The  branches  of  the  external  popliteal  nerve  are  the  communi- 
cans peronei,  cutaneous  and  articular. 

The  communicans  peronei,  proceeding  from  the  external  pop- 
liteal near  the  head  of  the  fibula,  crosses  the  external  origin  of 
the  gastrocnemius  muscle,  and,  piercing  the  deep  fascia,  descends 
to  the  middle  of  the  leg,  where  it  joins  the  external  saphenous 
nerve.  It  gives  off  one  or  two  cutaneous  filaments  in  its  course. 

The  cutaneous  branch  descends  the  outer  side  of  the  leg,  sup- 
plying the  integument. 

The  articular  branches  take  the  course  of  the  external  articu- 
lar arteries  to  the  knee-joint,  to  which  they  are  distributed. 

Dissection  of  the  Leg. 

The  leg  is  naturally  divided  into  three  regions,  anterior  tibial, 
jibular,  and  posterior  tibial.  Each  region  is  composed  of  its 


DISSECTION  OF  THE  LEO.  429 

appropriate  muscles,  vessels,  and  nerves.     Those  of  the  anterior 
tibial  region  may  be  thus  arranged  : — 

Superficial  to  the  fascia.  Beneath  the  fascia. 

Tibial  recurrent  artery,  Tibialis  anticus, 

Internal  saphenous  vein,  Extensor  longus  digitorum, 

Internal  saphenous  nerve,  Peroneus  tertius, 

Musculo-cutaneous  nerve,  Extensor  proprius  pollicis, 

Anterior  tibial  artery, 
Anterior  tibial  nerve. 

The  student  will  find  it  convenient,  before  commencing  the  dissection 
of  the  leg,  to  separate  the  limb  from  the  rest  of  the  body,  by  dividing  the 
muscles,  and  sawing  across  the  femur  at  about  its  middle.  This  step  is 
better  than  disarticulating  at  the  hip-joint,  as  it  gives  him  an  opportu- 
nity, at  an  after  period,  of  studying  the  ligaments  of  the  hip.  The  dis- 
section of  the  anterior  tibial  region  is  to  be  commenced  by  carrying  an 
incision  along  the  middle  of  the  leg,  midway  between  the  tibia  and  the 
fibula,  from  the  knee  to  the  ankle,  and  bounding  it  inferiorly  by  a  trans- 
verse incision,  extending  from  one  malleolus  to  the  other.  And  to  ex- 
pose the  tendons  on  the  dorsum  of  the  foot,  the  longitudinal  incision  may 
be  carried  onwards  to  the  outer  side  of  the  base  of  the  great  toe,  and  ter- 
minated by  another  incision  directed  across  the  heads  of  the  metatarsal 
bones. 

When  the  integument  of  these  two  regions  has  been  turned 
aside,  a  small  artery  must  be  sought  for  near  the  head  of  the 
tibia,  it  pierces  the  deep  fascia,  and  turns  upwards  upon  the 
knee-joint,  to  inosculate  with  the  articular  arteries.  This  is  the 
recurrent  branch  of  the  anterior  tibial  artery. 

In  dissecting  the  superficial  fascia  from  the  anterior  tibial  region,  it  is 
desirable  to  commence  by  finding  the  situation  of  the  superficial  vessels 
and  nerves,  and  take  them  as  a  point  of  departure,  and  a  guide  to  the 
direction  in  which  the  dissection  should  be  pursued.  Unless  this  be  done, 
there  is  a  danger  of  cutting  away  branches  of  vessels  or  filaments  of 
nerves  without  perceiving  them.  Although  this  advice  is  suggested  by 
the  dissection  of  the  present  region,  it  is  equally  applicable  to  all  the 
regions  of  the  body.  The  young  dissector  must  apply  to  one  of  his  seniors 
or  to  the  Demonstrator  to  have  the  precise  spot  pointed  out  to  him, 
where  superficial  vessels  or  nerves  are  to  be  found.  The  following 
remarks  will  aid  him  in  his  search. 

On  the  inner  side  of  the  leg  will  be  found  the  internal  saphe- 
nous vein,  and  the  numerous  branches  which  empty  themselves 
into  it  in  its  course.  This  vein  commences  on  the  inner  side  of 
the  dorsum  of  the  foot,  where  it  receives  the  inner  termination 
of  a  venous  arch  which  lies  across  the  metatarsal  bones.  It  then 
runs  in  front  of  the  inner  malleolus  and  ascends  the  inner  side  of 
the  leg;  passes  behind  the  inner  condyle  of  the  femur,  and  is  con- 
tinued upwards  along  the  inner  side  of  the  thigh  to  the  saphenous 
opening. 

In  company  with  the  internal  saphenous  vein  is  the  internal 


430  THE  DISSECTOR. 

saphenous  nerve,  a  branch  of  the  anterior  crural.  This  nerve 
pierces  the  fascia  lata  at  the  knee,  and  gives  off  several  cutaneous 
filaments  in  its  course  downwards.  Below  the  ankle  it  is  distri- 
buted to  the  inner  side  of  the  foot  and  great  toe.  In  the  neigh- 
borhood of  the  long  saphenous  nerve  may  be  found  the  cutaneous 
branch  of  the  obturator  nerve,  which  unites  with  the  internal  saphe- 
nous, and  supplies  the  integument  of  the  inner  side  of  the  leg  as 
far  as  its  middle. 

Taking  its  course  along  the  outer  border  of  the  anterior  tibial 
region,  is  the  cutaneous  branch  of  the  external  popliteal  nerve ; 
and,  at  the  lower  third  of  the  leg  and  close  to  the  fibula,  the 
musculo-cutaneous  nerve  will  be  found  piercing  the  deep  fascia, 
and  dividing  into  its  two  cutaneous  branches.  These  branches 
pass  downwards  in  front  of  the  ankle  to  the  dorsum  of  the  foot 
and  toes,  to  which  they  are  distributed  ;  the  external  branch,  the 
larger  of  the  two  supplying  three  toes  and  a  half;  the  internal 
branch  one  toe  and  a  half. 

The  DEEP  FASCIA  is  strong  and  tendinous,  and  firmly  attached 
to  the  tibia  and  fibula.  By  its  internal  surface  it  gives  origin  to 
the  muscles  of  this  region,  and  between  the  two  malleoli  it  forms 
a  dense  band,  called  anterior  annular  ligament,  which  binds  down 
the  tendons  of  the  extensor  muscles,  and  forms  separate  canals 
for  them  in  their  passage  forwards  to  the  dorsum  of  the  foot.  The 
anterior  annular  ligament  consists  of  two  portions,  upper  and 
lower ; — the  upper  portion  is  the  broad  band  connected  with  the 
tibia  and  fibula,  now  described.  The  lower  portion  is  placed  on 
the  dorsum  of  the  foot,  extending  between  the  inner  malleolus 
and  the  outer  surface  of  the  os  calcis :  the  inner  extremity  has, 
besides,  a  second  attachment  to  the  plantar  fascia,  with  which  it 
is  continuous. 

An  incision  may  now  be  made  through  the  deep  fascia,  in  the  course 
of  a  line  drawn  from  the  midpoint  between  the  head  of  the  fibula  and 
spine  of  the  tibia,  to  midway  between  the  inner  and  outer  malleolus. 
This  will  mark  the  course  of  the  anterior  tibial  artery ;  and  an  incision 
made  in  any  part  of  this  line  will  expose  that  vessel  in  its  course  between 
the  muscles.  The  structures  to  be  divided  are  the  same  as  in  any  other 
part  of  the  body.  (  Vide  Chap.  I.) 

The  deep  fascia  is  easily  separated  from  the  muscles  in  the  lower 
part  of  the  leg,  but  above  it  is  closely  connected  to  them,  and 
cannot  be  removed  without  dividing  some  of  their  fibres.  When 
removing  the  deep  fascia,  the  anterior  annular  ligament  should 
be  left  uninjured. 

Muscles  of  the  Anterior  Tibial  Region. 
Tibialis  anticus, 
Extensor  longus  digitorum, 
Peroneus  tertius, 
Extensor  proprius  pollicis. 


TIBIALIS  ANTICUS — EXTENSORS. 


431 


Fig.  130. 


The  TIBIALIS  ANTICUS  muscle  (flexor  tarsi  tibialis)  arises  from 
the  outer  tuberosity  and  upper  two-thirds  of  the  tibia,  from  the 
interosseous  membrane,  intermuscular  fascia,  and  deep  fascia;  its 
tendon  passes  through  a  distinct  sheath  in  the  annular  ligament, 
and  is  inserted  into  the  inner  and  under  side  of  the  internal  cunei- 
form bone,  and  base  of  the  metatarsal  bone  of  the  great  toe. 

The  EXTENSOR  LONGUS  DiGiTORUM  arises  from  the  outer  tube- 
rosity of  the  tibia,  from  the  head  and  upper  three-fourths  of  the 
fibula,  from  the  interosseous  membrane,  intermuscular  fascia,  and 
deep  fascia.  Below  it  divides  into  four 
tendons,  which  pass  beneath  the  annular 
ligament,  to  be  inserted  into  the  second 
and  third  phalanges  of  the  four  lesser 
toes.  The  mode  of  insertion  of  the  ex- 
tensor tendons,  both  in  the  hand  and  in 
the  foot  is  remarkable  (Fig.  116)  ;  each 
tendon  spreads  into  a  broad  aponeurosis, 
which  is  situated  over  the  first  phalanx, 
and  receives  on  its  borders  the  insertion 
of  the  lumbricales  and  interossei ;  this 
aponeurosis  divides  into  three  slips  ;  the 
middle  slip  is  inserted  into  the  base  of 
the  second  phalanx,  and  the  two  lateral 
slips  are  continued  onwards  to  be  inserted 
into  the  base  of  the  third. 

The  PERONEUS  TERTIUS  (flexor  tarsi 
fibularis)  arises  from  the  lower  fourth  of 
the  fibula,  and  intermuscular  fascia ;  it 
is  inserted  into  the  base  of  the  metatarsal 
bone  of  th^  little  toe.  Although  it  ap- 
pears to  be  merely  a  part  of  the  extensor 
longus  digitorum,  it  may  be  looked  upon 
as  analogous  to  the  flexor  carpi  ulnaris 
of  the  forearm.  Sometimes  it  is  alto- 
gether wanting. 

The  EXTENSOR  PROPRIUS  POLLICIS  lies 

between  the  tibialis  anticus  and  extensor 
longus  digitorum.  It  arises  from  the 
lower  two-thirds  of  the  fibula  and  inter- 

THE  MUSCLES  OF  THE  ANTERIOR  TIBIAL  REGION. — 1.  The  extensor  muscles 
inserted  into  the  patella.  2.  The  subcutaneous  surface  of  the  tibia.  3.  The 
til. i:ilis  anticus.  4.  The  extensor  communis  digitorum.  5.  The  extensor  pro- 
prius  pollicis.  6.  The  peroneus  tertius.  7.  The  peroneus  longus.  8.  The 
peroneus  brevis.  9,  9.  The  borders  of  the  soleus  muscle.  10.  A  part  of  the 
inner  belly  of  the  gastrocnemius.  11.  The  extensor  brevis  digitorum  ;  the  ten- 
don in  front  of  this  number  is  that  of  the  peroneus  tertius  ;  and  that  behind  it, 
the  tendon  of  the  peroneus  brevis. 


432 


THE   DISSECTOR. 


osseous  membrane.  Its  tendon  passes  through  a  distinct  sheath 
in  the  annular  ligament,  and  is  inserted  into  the  base  of  the  last 
phalanx  of  the  great  toe. 

ACTIONS. — The  tibialis  anticus  and  peroneus  ter- 
Fig.  131.  tins  are  direct  flexors  of  the  tarsus  upon  the  leg  ; 

acting  in  conjunction  with  the  tibialis  posticus, 
and  peroneus  longus  and  brevis,  they  direct  the 
foot  either  inwards  or  outwards,  and  preserve  its 
flatness  in  progression.  The  extensor  longus  digi- 
torum,  and  extensor  proprius  pollicis,  are  direct 
extensors  of  the  phalanges :  but  continuing  their 
action,  they  assist  the  tibialis  anticus  and  peroneus 
tertius,  in  flexing  the  entire  foot  upon  the  leg. 
Taking  their  origin  from  below,  they  increase  the 
stability  of  the  ankle. 

Vessels  and  Nerves  of  the  Anterior  Tibial 
Region. 

We  have  seen  in  a  previous  section  that  the 
popliteal  artery  divides  into  the  anterior  and 
posterior  tibial. 

The  ANTERIOR  TIBIAL  passes  forwards  be- 
tween the  two  heads  of  the  tibialis  posticus 
muscle,  then  through  the  opening  in  the  upper 
part  of  the  interosseous  membrane,  to  the 
anterior  tibial  region.  From  this  point  it 
runs  down  the  anterior  aspect  of  the  leg  to 
the  ankle-joint,  where  it  becomes  the  dorsalis 
pedis.  In  its  course  it  rests  upon  the  inter- 
osseous  membrane,  the  lower  part  of  the  tibia, 
and  the  anterior  ligament  of  the  joint.  In 
the  upper  third  of  its  course  it  is  situated  be- 
tween the  tibialis  anticus  and  extensor  longus 
digitorum ;  lower  down  between  the  tibialis 
anticus  and  extensor  proprius  pollicis ;  and 
just  before  it  reaches  the  ankle  it  is  crossed 
by  the  tendon  of  the  extensor  proprius  pol- 

THE  ANTERIOR  ASPECT  OF  THE  LEG  AND  FOOT,  SHOWING  THE  ANTERIOR 
TIBIAL  AND  DORSALIS  PEDIS  ARTERIES,  WITH  THEIR  BRANCHES. — 1.  The 
tendon  of  insertion  of  the  quadriceps,  extensor  muscle.  2.  The  insertion  of  the 
ligamentum  patellae  into  the  lower  border  of  the  patella.  3.  The  tibia.  4.  The 
extensor  proprius  pollicis  muscle.  5.  The  extensor  longus  digitorum.  6.  The 
peronei  muscles.  7.  The  inner  belly  of  the  gastrocnemius  and  the  soleus.  8. 
The  annular  ligament  beneath  which  the  extensor  tendons  and  the  anterior  tibial 
artery  pass  into  the  dorsum  of  the  foot.  9.  The  anterior  tibial  artery.  10.  Its 
recurrent  branch  inosculating  with  (2)  the  inferior  articular,  and  (1)  the  super- 
articular  artery,  branches  of  the  popliteal.  11.  The  internal  malleolar  artery. 
17.  The  external  malleolar  inosculating  with  the  anterior  peroneal  artery,  12. 
13.  The  dorsalispedis  artery.  14.  The  tarseaand  metatarsea  arteries  ;  the  tarsea 
is  nearest  the  ankle,  the  metatarsea  is  seen  giving  off  the  interosseae.  15.  The 
dorsalis  hallucis  artery.  16.  The  communicating  branch. 


ANTERIOR  TIBIAL  ARTERY.  433 

licis,  and  becomes  placed  between  that  tendon  and  the  tendons 
of  the  extensor  longus  digitorum.  Its  immediate  relations  are, 
the  venae  comites,  and  the  anterior  tibial  nerve  :  the  latter  lies  at 
first  to  its  outer  side ;  about  the  middle  of  the  leg  it  becomes 
placed  in  front  of  the  artery ;  and  at  the  ankle  is  again  at  its 
outer  side. 

Operations. — The  anterior  tibial  artery  may  be  tied  in  any  part  of  its 
course  (after  it  lias  escaped  through  the  opening  in  the  interosseoua 
membrane),  by  making  an  incision  in  the  direction  of  a  line  drawn  from 
the  midpoint,  between  the  anterior  borders  of  the  tibia  and  fibula  in  the 
upper  third  of  the  leg,  to  the  middle  of  the  ankle. 

The  operation  in  the  upper  third  of  the  course  of  the  artery  is  one  of 
considerable  difficulty. — 1st.  On  account  of  the  absence  of  any  positive 
guide  to  the  interspace  between  the  tibialis  anticus  and  extensor  longus 
digitorum  muscles  ;  2d.  On  account  of  the  great  depth  of  the  artery  ;  and 
3dly.  On  account  of  the  unyielding  nature  of  the  deep  fascia,  which  con- 
stricts the  external  orifice  of  the  wound.  In  consequence  of  these  im- 
pediments, the  artery  is  never  operated  upon  in  this  situation,  excepting 
for  the  purpose  of  securing  both  ends  of  the  vessel  in  accidental  wounds. 
The  incision  in  the  integument  and  deep  fascia  must  be  four  inches  in 
length.  The  artery  has  a  vein  to  either  side,  vence  comites  ;  the  nerve  lies 
to  its  outer  side. 

In  the  middle  third  of  the  leg,  the  incision  is  to  be  made  in  the  same 
direction,  and  about  three  inches  in  length.  The  structures  to  be  divided 
are  the  integument,  superficial  fascia,  and  deep  fascia.  Then  the  interspace 
between  the  tibialis  anticus  and  extensor  proprius  pollicis  is  to  be  found, 
and  the  two  muscles  separated.  Lying  at  the  bottom  of  the  interval  be- 
tween them,  and  supported  by  the  interosseous  membrane,  will  be  seen 
the  artery,  accompanied  by  its  venae  comites,  and  having  the  anterior 
tibial  nerve  resting  upon  it.  The  nerve  is  to  be  drawn  carefully  aside, 
the  sheath  of  the  vessels  opened,  and  the  ligature  conveyed,  by  means 
of  the  aneurism  needle,  around  the  artery. 

In  the  lower  third  of  the  leg,  an  incision  in  the  same  direction  but  two 
inches  in  length  will  suffice.  The  structures  to  be  cut  through  are  the 
same  as  in  the  former  operation.  The  artery  will  be  found  resting  on  the 
bone,  between  the  tendons  of  the  tibialis  anticus  and  extensor  longus 
digitorum,  or,  nearer  to  the  ankle,  between  the  tendons  of  the  extensor 
longus  digitorum  and  extensor  proprius  pollicis.  The  relations  to  the 
veins  are  the  same  ;  the  nerve  lies  to  its  outer  side. 

The  branches  of  the  anterior  tibial  artery  are  the — 
Recurrent,  External  malleolar, 

Muscular,  Internal  malleolar. 

The  recurrent  branch  passes  upwards  to  the  front  of  the  knee- 
joint  upon  which  it  is  distributed,  anastomosing  with  the  articular 
arteries.  It  pierces  the  origin  of  the  tibialis  anticus  muscle. 

The  muscular  branches  supply  the  muscles  of  the  anterior  tibial 
region. 

The  malleolar  arteries  are  distributed  to  the  ankle-joint ;  the 
external  passing  beneath  the  tendons  of  the  extensor  longus 
digitorum  and  peroneus  tertius,  and  inosculating  with  the  ante- 
37 


434  THE   DISSECTOR. 

rior  peroneal  artery  and  dorsalis  pedis  ;  the  internal  beneath  the 
tendons  of  the  extensor  proprius  pollicis  and  tibialis  anticus,  in- 
osculates with  branches  of  the  posterior  tibial  and  internal  plantar 
artery. 

The  ANTERIOR  TIBIAL  NERVE  (inter osseous ,  Fig.  132,  13),  com- 
mences at  the  bifurcation  of  the  external  popliteal  upon  the  neck 
of  the  fibula,  and  passes  beneath  the  upper  part  of  the  extensor 
longus  digitorum,  to  reach  the  outer  side  of  the  anterior  tibial 
artery,  just  as  that  vessel  has  passed  through  the  opening  in  the 
interosseous  membrane.  It  descends  with  the  artery,  lying  at 
first  to  its  outer  side,  and  then  in  front  of  it,  and  near  the  ankle 
becomes  again  placed  to  its  outer  side.  It  supplies  the  mus- 
cles of  the  anterior  tibial  region,  and  on  the  foot  accompanies 
the  dorsalis  pedis  artery  to  the  space  between  the  great  and 
second  toe. 

Dorsal  Region  of  the  Foot. 

The  deep  fascia  in  this  region  is  extremely  thin,  and  can 
hardly  be  said  to  exist :  the  muscles  on  the  dorsum  of  the  foot 
are — 

Extensor  brevis  digitorum, 

4  Dorsal  interossei  {   bicipital 

The  EXTENSOR  BREVIS  DIGITORUM  muscle  arises  from  the  outer 
side  of  the  os  calcis,  crosses  the  foot  obliquely,  and  terminates 
in  four  tendons,  the  innermost  of  which  is  inserted  into  the  base 
of  the  first  phalanx  of  the  great  toe,  and  the  other  three  into 
the  sides  of  the  long  extensor  tendons  of  the  second,  third,  and 
fourth  toes. 

The  DORSAL  INTEROSSEI  muscles  are  placed  between  the  meta- 
tarsal  bones;  they  resemble  the  analogous  muscles  of  the  hand 
in  arising  by  two  heads  from  the  adjacent  sides  of  the  metatarsal 
bones ;  their  tendons  are  inserted  into  the  base  of  the  first  pha- 
lanx, and  into  the  digital  expansion  of  the  tendons  of  the  long 
extensor. 

The  first  dorsal  interosseous  is  inserted  into  the  inner  side  of 
the  second  toe,  and  is  therefore  an  adductor ;  the  other  three  are 
inserted  into  the  outer  side  of  the  second,  third,  and  fourth  toes, 
and  are  therefore  abductors. 

Communicating  arteries  (posterior  perforantes),  between  the 
dorsum  and  sole  of  the  foot,  pass  between  the  bifid  origins  of 
these  muscles. 

The  ARTERY  of  the  dorsum  of  the  foot,  DORSALIS  PEDIS,  is  the 
continuation  of  the  anterior  tibial ;  it  runs  along  the  dorsum  of 
the  foot,  from  the  ankle  to  the  base  of  the  first  metatarsal  space, 
where  it  gives  off  a  branch,  the  dorsalis  pollicis,  and  then  dips 


DORSALIS  PEDIS  ARTERY.  435 

between  the  two  heads  of  the  first  dorsal  interosseous  muscle  into 
the  sole  of  the  foot,  and  becomes  continuous  with  the  deep 
plantar  arch.  In  its  course  along  the  foot  it  gives  off  the  tarsea 
and  metatarsea,  and  is  placed  on  the  outer  side  of  the  tendon  of 
the  extensor  proprius  pollicis;  on  its  fibular  side  it  has  the 
tendon  of  the  extensor  longus  digitorum,  and  near  its  termi- 
nation is  crossed  by  the  inner  tendon  of  the  extensor  brevis 
digitorum. 

Operation. — The  dorsalis  pedis  artery  is  to  be  exposed,  by  making  an 
incision  two  inches  in  length  along  the  external  border  of  the  tendon  of 
the  extensor  proprius  pollicis  muscle,  beginning  at  the  ankle-joint.  The 
artery,  accompanied  by  its  two  veins  and  nerve,  rests  upon  the  bones  of 
the  tarsus,  between  the  tendons  of  the  extensor  proprius  pollicis  and  ex- 
tensor longus  digitorum.  Near  the  base  of  the  metatarsal  bones  it  is 
crossed  by  the  innermost  tendon  of  the  extensor  brevis  digitorum. 

The  tarsea  crosses  the  dorsum  of  the  foot  in  an  arched  direc- 
tion, beneath  the  extensor  brevis  digitorum  muscle.  It  supplies 
the  articulations  of  the  tarsal  bones,  and  inosculates  at  the  outer 
border  of  the  foot  with  the  external  malleolar,  peroneal  arteries, 
and  external  plantar. 

The  metatarsea  forms  a  similar  arch  across  the  bases  of  the 
metatarsal  bones,  and  terminates  on  the  outer  side  of  the  foot  by 
inosculating  with  the  tarsea,  and  external  plantar  artery.  From 
its  convex  side  the  metatarsea  gives  off  three  branches,  the  in- 
terossece,  which  pass  forwards  on  the  interossei  muscles  and  divide 
into  branches  (dorsal  collateral),  which  supply  the  sides  of  the 
toes  between  which  they  are  placed.  Near  their  origin  the 
interosseae  receive  the  posterior  perforating  branches  from  the 
plantar  arch;  and  at  their  bifurcation  they  are  joined  by  the  an- 
terior perforating  branches  from  the  digital  arteries.  The  inter- 
osseous  artery  of  the  fourth  interosseous  space,  in  addition  to 
the  two  dorsal  collateral  branches  into  which  it  bifurcates,  sends 
a  third  to  the  outer  side  of  the  little  toe. 

The  dorsalis  pollicis  runs  forward  upon  the  first  dorsal  inter- 
osseous muscle,  and  at  the  base  of  the  first  phalanx  divides  into 
two  branches,  one  of  which  passes  beneath  the  tendon  of  the  ex- 
tensor proprius  pollicis,  and  is  distributed  to  the  inner  border  of 
the  great  toe  ;  the  other  bifurcates  into  two  collateral  branches, 
which  supply  the  adjacent  sides  of  the  great  and  second  toe. 

While  in  the  metatarsal  space  the  dorsalis  pedis  artery  gives 
off  another  branch,  magna  pollicis,  which  sends  a  digital  branch 
to  the  inner  border  of  the  great  toe,  and  then  bifurcates  to  sup- 
ply the  collateral  digital  branches  of  the  great  and  second  toe. 

The  VEINS  of  the  dorsum  of  the  foot  are  a  venous  arch  which 
lies  across  the  metatarsus,  and  the  internal  and  external  saphenons 
veins.  The  venous  arch  receives  the  digital  veins  by  its  convex 
side,  and  terminates  in  the  saphenous  veins. 


436  THE   DISSECTOR. 

The  internal  saphenous  vein,  taking  its  origin  by  the  veins  of 
the  great  toe  and  inner  termination  of  the  venous  arch,  passes 
upwards  along  the  inner  border  of  the  foot,  and  in  front  of  the 
inner  ankle  to  the  side  of  the  leg,  whence  it  is  continued  to  the 
saphenous  opening. 

The  external  saphenous  vein  commences  in  a  similar  manner  on 
the  outer  side  of  the  little  toe  and  side  of  the  foot ;  it  receives 
the  outer  termination  of  the  venous  arch,  passes  behind  the  outer 
ankle,  and  ascends  along  the  back  of  the  leg  to  the  popliteal 
region,  where  it  enters  an  opening  in  the  deep  fascia  and  joins 
the  popliteal  vein. 

The  NERVES  distributed  upon  the  dorsum  of  the  foot  are  five 
in  number,  namely,  the  internal  and  external  branches  of  the 
musculo-cutaneous  nerve ;  the  internal  and  external  saphenous 
nerves,  and  the  anterior  tibial. 

The  cutaneous  branches  of  the  musculo-cutaneous  nerve  divide 
into  a  leash  of  branches  which  spread  out  upon  the  dorsum  of 
the  foot  in  their  course  to  the  toes.  The  internal  branch,  the 
smaller  of  the  two,  is  distributed  to  the  inner  side  of  the  foot  and 
great  toe,  and  communicates  with  the  anterior  tibial  and  internal 
saphenous.  The  external,  or  larger  branch,  supplies  the  adja- 
cent sides  of  the  second  and  third,  third  and  fourth,  and  fourth 
and  fifth  toes,  and  communicates  with  the  external  saphenous. 

The  internal  or  long  saphenous  nerve  passes  along  the  inner 
side  of  the  foot  as  far  as  the  base  of  the  metatarsus,  and  com- 
municates with  the  internal  cutaneous  nerve. 

The  short  or  external  saphenous  nerve  advances  along  the  outer 
border  of  the  foot  from  behind  the  outer  ankle.  It  is  distributed 
to  the  outer  side  of  the  little  toe,  and  sometimes  its  inner  side 
and  the  adjacent  side  of  the  next.  It  communicates  with  the 
external  cutaneous  nerve. 

The  anterior  tibial  nerve  gives  off  a  large  branch  to  the  ex- 
tensor brevis  digitorum  muscle,  and  becoming  superficial  on  the 
first  interosseous  muscle,  is  distributed  to  the  adjacent  sides  of 
the  great  and  second  toe ;  while  on  the  interosseous  muscle  it 
receives  a  branch  of  communication  from  the  internal  cutaneous 
nerve,  and  sometimes  this  branch  is  so  large  as  to  supersede  the 
anterior  tibial  in  its  distribution.  The  branch  to  the  extensor 
brevis  digitorum,  after  supplying  the  muscle,  becomes  gangliform 
and  distributes  branches  to  the  articulations  of  the  tarsus. 

Fibular  Region. 

If  the  leg  be  turned  upon  its  inner  side  and  the  deep  fascia  removed 
from  over  the  fibula,  two  muscles  will  be  exposed  which  arise  from  that 
bone :  these  are  the  peroneus  longus  and  brevis.  They  are  separated 
from  the  muscles  before  and  behind  by  intermuscular  septa,  from  which 


POSTERIOR  TIBIAL  REGION.  437 

they  partly  take  their  origin.  At  the  outer  ankle  the  deep  fascia  is 
thickened,  and,  extending  from  the  external  malleolus  to  the  side  of  the 
os  calcis,  constitutes  the  external  annular  ligament.  This  ligamentous 
band  forms  a  sheath  for  the  peronei  muscles  in  their  passage  behind  the 
outer  ankle ;  the  sheath  is  lined  bjjr  synovial  membrane. 

The  PERONEUS  LONGUS  (rtfpov*?,  fibula,  extensor  tarsi  fibularia 
longior)  arises  from  the  head  and  upper  half  of  the  fibula ;  also 
from  the  deep  fascia  and  intermuscular  septa  :  its  tendon  passes 
behind  the  outer  malleolus  to  a  groove  in  the  cuboid  bone, 
through  which  it  proceeds  obliquely  across  the  foot  to  be  in- 
serted into  the  base  of  the  metatarsal  bone  of  the  great  toe.  The 
tendon  is  thickened  where  it  passes  behind  the  external  malleo- 
lus, and  a  sesamoid  bone  is  developed  in  that  part  which  is 
lodged  in  the  groove  of  the  cuboid  bone. 

The  PERONEUS  BREVIS  (extensor  tarsi  fibularis  brevior)  arises 
from  the  lower  half  of  the  fibula  and  from  the  intermuscular 
septa ;  its  tendon  passes  behind  the  external  malleolus,  with  the 
tendon  of  the  preceding  muscle,  and  through  a  groove  in  the  os 
calcis  to  be  inserted  into  the  base  of  the  metatarsal  bone  of  the 
little  toe. 

ACTIONS. — The  peronei  muscles  are  extensors  of  the  foot  conjointly  with 
the  tibialis  posticus.  They  antagonize  the  tibialis  anticus  and  peroneus 
tertius,  which  are  flexors  of  the  foot.  The  whole  of  these  muscles  acting 
together  tend  to  maintain  the  flatness  of  the  foot,  so  necessary  to  security 
in  walking. 

There  is  no  artery  in  this  region,  but  if  the  peroneus  longus 
muscle  be  carefully  turned  aside  from  its  origin,  the  external 
popliteal  or  peroneal  nerve  will  be  seen  to  give  off  a  small  re- 
current branch,  which  takes  the  course  of  the  recurrent  tibial 
artery  to  the  front  of  the  knee ;  and  then  divides  into  its  two 
terminal  branches,  the  anterior  tibial  nerve  and  musculo- cutaneous. 

The  anterior  tibial  nerve  may  now  be  seen  piercing  the  head  of 
the  extensor  longus  digitorum  to  reach  the  anterior  tibial  artery; 
its  course  has  already  been  described,  page  434. 

The  musculo-cutaneous,  the  proper  nerve  of  the  region,  passes 
downwards  in  the  substance  of  the  peroneus  longus  ;  it  then  gets 
between  the  peroneus  longus  and  brevis  ;  then  between  the  pe- 
ronei and  the  extensor  longus  digitorum  ;  and  at  the  lower  third 
of  the  leg  pierces  the  deep  fascia  and  divides  into  the  internal 
and  external  cutaneous  nerves  of  the  foot.  In  its  course  among 
the  muscles  the  nerve  gives  several  branches  to  the  peronei.  The 
cutaneous  branches  have  been  already  described,  page  436. 

Posterior  Tibial  Region. 

This  region  is  best  dissected  by  making  an  incision  from  the  middle  of 
the  popliteal  space,  down  the  middle  of  the  posterior  part  of  the  leg,  to 
the  tuberosity  of  the  os  calcis,  bounding  it  inferiorly  by  a  transverse  in- 

37* 


438 


THE  DISSECTOR. 


Fig.  132. 


cision  to  each  raalleolus.  Turning  aside  the  two  flaps  of  integument,  the 
superficial  fascia  is  brought  into  view,  and  between  its  two  layers  will  be 
found  the  superficial  vessels  and  nerves.  In  the  middle  line  is  the 
external  saphenous  vein,  accompanied  above  by 
the  lesser  ischiatic  nerve,  and  below,  by  the  ex- 
ternal saphenous  nerve.  On  the  inner  side  of 
the  leg  is  the  internal  saphenous  vein  and  nerve, 
with  the  termination  of  the  internal  cutaneous 
nerve.  On  the  outer  side  are  several  cutaneous 
branches  from  the  external  popliteal,  one  of  which 
is  the  communicans  peronei. 

The  external  saphenous  vein  (Fig.  129,  s) 
commences  on  the  outer  side  of  the  little 
toe,  and  after  receiving  the  external  termi- 
nation of  the  venous  arch,  passes  along  the 
outer  side  of  the  foot,  behind  the  external 
malleolus,  and  up  the  middle  of  the  back  of 
the  leg  to  the  popliteal  region.  In  its 
course  along  the  leg  it  lies  in  the  groove 
between  the  two  bellies  of  the  gastrocne- 
mius  muscle,  and  in  the  ham  pierces  the 
deep  fascia  to  join  the  popliteal  vein. 

The  lesser  ischiatic  nerve  pierces  the  popli- 
teal fascia  and  descends  by  the  side  of  the 
external  saphenous  vein  to  the  point  of 
emergence  of  the  external  saphenous  nerve, 
with  which  it  joins,  after  giving  off  several 
cutaneous  twigs. 

The  short  or  external  saphenous  nerve  (Fig. 
129,  7  ;  Fig.  132,  i  e)  will  be  found  lying  by 
the  side  of  the  external  saphenous  vein  ;  in 
the  lower  part  of  the  leg  it  pierces  the  deep 
fascia  just  below  the  gastrocnemic  groove, 
and  descends  with  the  external  saphenous 
vein ;  passes  behind  the  external  malleolus 
and  along  the  outer  border  of  the  foot.  It 
is  distributed  to  the  outer  part  of  the  foot 
and  little  toe,  and  communicates  with  the 
external  cutaneous  nerve. 

A  DIAGRAM  SHOWING  THE  FORMATION  AND  BRANCHES  or  THE  SACRAL 
PLEXUS. — 1.  The  lumbo-sacral  nerve,  descending  to  join  the  sacral  plexus,  and 
giving  off  a  large  branch.  2.  The  gluteal  nerve.  3.  The  anterior  branches  of 
the  four  upper  sacral  nerves.  4.  The  sacral  plexus.  5.  The  internal  pudic 
nerve.  6.  The  lesser  ischiatic  nerve.  7.  The  great  ischiatic  nerve.  8.  The 
peroneal  nerve.  9.  The  popliteal  nerve.  10.  Its  sural  branches.  11.  The 
posterior  tibial  nerve  dividing  inferiorly  into  the  two  plantar  nerves,  12.  13. 
The  anterior  tibial  nerve.  14.  The  musculo-cutaneous  nerve,  its  muscular  por- 
tion. 15.  Its  cutaneous  portion.  16.  The  external  saphenous  nerve,  formed 
by  the  union  of  the  communicans  poplitei,  and  communicans  peronei. 


GASTROCNEMIU8. 


439 


The  internal  saphenous  vein  and  nerve  have  been  described 
with  the  dissection  of  the  anterior  tibial  region.  The  internal 
cutaneous  branches  of  the  anterior  crural  are  distributed  to  the 
integument  of  the  inner  side  of  the  calf  behind  the  internal  sa- 
phenous vein. 

The  communicans  peronei,  a  branch  of  the  external  popliteal 
nerve,  pierces  the  deep  fascia  near  the  head  of  the  fibula,  and 
descends  to  the  external  saphenous  nerve,  which  it  joins  ;  in  its 
course  it  gives  off  cutaneous  filaments.  Along  the  outer  border 
of  the  leg  are  other  cutaneous  branches,  de- 
rived from  the  external  politeal  nerve.  Fig- 133. 

The  DEEP  FASCIA,  in  the  upper  part  of  this 
region,  is  thin :  below  it  is  thicker ;  on  the 
inner  side  it  is  connected  with  the  tibia,  and 
externally  is  continuous  with  the  deep  fascia 
of  the  front  of  the  leg.     If  the  deep  fascia 
be  turned  aside,  the  three  muscles  forming 
the  superficial  group  of  the  posterior  tibial 
region  will  be  brought  into  view  ;  they  are — 
Gastrocnemius, 
Plantaris, 
Soleus. 

The      GASTROCNEMIUS      (yaatpoxvypiov,     the 

bellied  part  of  the  leg)  arises  by  two  heads 
from  the  two  condyles  of  the  femur,  the  inner 
head  being  the  longest.  They  unite  to  form 
the  beautiful  muscle  so  characteristic  of  this 
region  of  the  limb.  It  is  inserted,  by  means 
of  the  tendo  Achillis,  into  the  lower  part  of 
the  poster  tuberosity  of  the  os  calcis,  a  syno- 
vial  bursa  being  placed  between  the  tendon 
and  the  upper  part  of  the  tuberosity.  The 
gastrocnemius  must  be  removed  from  its 
origin,  and  turned  down,  in  order  to  expose 
the  next  muscle. 

The  PLANTARIS  (planta,  the  sole  of  the 
foot),  an  extremely  diminutive  muscle,  situ- 
ated between  the  gastrocnemius  and  soleus, 
arises  from  the  outer  condyle  of  the  femur, 

THE  SUPERFICIAL  MUSCLES  OP  THE  POSTERIOR  ASPECT  OF  THE  LEO. — 1. 
The  biceps  muscle  forming  the  outer  hamstring.  2.  The  tendons  forming  the 
inner  hamstring.  3  The  popliteal  space.  4.  The  gastrocnemius  muscle.  5, 
5.  The  solens.  6.  The  tendo- Achillis.  7.  The  posterior  tuberosity  of  the  os 
calcis.  8.  The  tendons  of  the  peroneus  longus  and  brevis  muscles  passing  be- 
hind the  outer  ankle.  9.  The  tendons  of  the  deep  layer  passing  into  the  foot 
behind  the  inner  ankle. 


440 


THE  DISSECTOR. 


and  is  inserted,  by  its  long  and  delicately  slender  tendon,  into 
the  posterior  tuberosity  of  the  os  calcis,  by  the  side  of  the  tendo 
Achillis.  It  crosses  between  the  gastrocnemius  and  soleus  in  its 
descent. 

The  SOLEUS  (solea,  a  sole)  is  the  broad  muscle  upon  which  the 
plantaris  rests.  It  arises  from  the  head  and  upper  third  of  the 
fibula,  from  the  oblique  line,  and  middle  third  of  the  tibia.  Its 
fibres  converge  to  the  tendo  Achillis,  by  which  it  is  inserted  into 

the  posterior  tuberosity  of  the  os  calcis. 

Fig.  134.  Between  the  fibular  and  tibial  origins  of  this 

muscle  is  a  tendinous  arch,  beneath  which  the 
popliteal  vessels  and  nerve  pass  into  the  leg.  The 
soleus  muscle  must  now  be  divided  along  its  exten- 
sive origin,  and  turned  down. 

ACTIONS. — The  three  muscles  of  the  calf  draw 
1 1/  &  r^?i  powerfully  on  the  os  calcis,  and  lift  the  heel ;  con- 
tinuing their  action,  they  raise  the  entire  body. 
This  action  is  attained  by  means  of  a  lever  of  the 
second  power,  the  fulcrum  (the  toes)  being  at  one 
end,  the  weight  (the  body  supported  on  the  tibia) 
in  the  middle,  and  the  power  (these  muscles)  at 
the  other  extremity. 

They  are  therefore  the  walking  muscles,  and  per- 
form all  movements  that  require  the  support  of  the 
whole  body  from  the  ground,  as  dancing,  leaping, 
&c.  Taking  their  fixed  point  from  below,  they 
steady  the  leg  upon  the  foot. 

An  inter  muscular  fascia  serves  to  separate 
the  superficial  from  the  deep  group,  and  by 
its  strong  attachments  to  the  bones  at  each 
side,  binds  down  the  muscles  closely  in  their 
places.  On  removing  this  fascia,  the  muscles 
of  the  deep  group  are  brought  clearly  into 
view  ;  they  are — 
Popliteus, 

Flexor  longus  pollicis, 
Flexor  longus  digitorum, 
Tibialis  posticus. 

The  POPLITEUS  muscle  (poples,  the  ham  of 
the  leg)  forms  the  floor  of  the  popliteal  region 

THE  DEEP  LAYER  OF  MUSCLES  OP  THE  POSTERIOR  TIBIAL  REGION. — 1.  The 
lower  extremity  of  the  femur.  2.  The  ligamentum  posticum  Winslowii.  3. 
The  tendon  of  the  semi-membranosus  muscle  dividing  into  its  three  slips.  4. 
The  internal  lateral  ligament  of  the  knee-joint.  5.  The  external  lateral  liga- 
ment. 6.  The  popliteus  muscle.  7.  The  flexor  longus  digitorum.  8.  The 
tibialus  posticus.  9.  The  flexor  longus  pollicis.  10.  The  peroneus  longus  mus- 
cle. 11.  The  peroneus  brevis.  12.  The  tendo-Achillis  divided  at  its  insertion 
into  the  os  calcis.  13.  The  tendons  of  the  tibialis  posticus  and  flexor  longus 
digitorum  muscles,  just  as  they  are  about  to  pass  beneath  the  internal  annular 
ligament  of  the  ankle  ;  the  interval  between  the  latter  tendon  and  the  tendon 
of  the  flexor  longus  pollicis  is  occupied  by  the  posterior  tibial  vessels  and  nerve. 


TIBIALIS  POST1CU8.  441 

at  its  lower  part,  and  is  bound  tightly  down  by  a  strong  fascia 
derived  from  the  middle  slip  of  the  tendon  of  the  semi-mem- 
branosus  muscle.  It  arises  by  a  rounded  tendon  from  a  deep 
groove  on  the  outer  side  of  the  external  condyle  of  the  femur, 
beneath  the  external  lateral  ligament  and  within  the  capsular 
ligament  of  the  joint.  It  spreads  obliquely  over  the  head  of  the 
tibia,  and  is  inserted  into  the  surface  of  bone  above  its  oblique 
line.  This  line  is  often  called,  from  being  the  limit  of  insertion 
of  the  popliteal  muscle,  popliteal  line. 

The  next  three  muscles  in  their  course  into  the  sole  of  the  foot 
pass  under  cover  of  an  aponeurosis  extended  between  the  inner 
malleolus  ^and  the  side  of  the  os  calcis,  the  internal  annular 
ligament.  'This  ligament  is  narrow  at  its  attachment  to  the  tibia 
and  broad  where  it  is  connected  with  the  os  calcis ;  above  it  is 
continuous  with  the  deep  fascia  of  the  leg,  and  below  gives  origin 
to  one  of  the  muscles  of  the  sole  of  the  foot.  Towards  the  bone 
it  sends  inwards  partitions  for  the  separation  of  the  tendons  and 
vessels. 

The  FLEXOR  LONGUS  POLLicis  is  the  most  superficial  of  the 
three  muscles.  It  arises  from  the  lower  two-thirds' of  the  fibula, 
passes  through  a  groove  in  the  astragalus  and  os  calcis,  which  is 
converted  by  tendinous  fibres  into  a  distinct  sheath  lined  by  syno- 
vial  membrane,  into  the  sole  of  the  foot,  and  is  inserted  into  the 
base  of  the  last  phalanx  of  the  great  toe. 

The  FLEXOR  LONGUS  DiGiTORUM  (perforans)  arises  from  the 
surface  of  the  tibia,  immediately  below  the  popliteal  line.  Its 
tendon  passes  through  a  sheath  common  to  it  and  the  tibialis 
posticus  behind  the  inner  malleolus ;  it  then  passes  through  a 
second  sheath  which  is  connected  with  a  groove  in  the  astragalus 
and  os  calcis,  into  the  sole  of  the  foot,  where  it  divides  into  four 
tendons,  which  are  inserted  into  the  base  of  the  last  phalanx  of 
the  four  lesser  toes,  perforating  the  tendons  of  the  flexor  brevis 
digitorum. 

The  flexor  longus  pollicis  must  now  be  removed  from  its  ori- 
gin, and  the  flexor  longus  digitorum  drawn  aside,  to  bring  into 
view  a  fascia  which  is  attached  on  either  side  to  the  tibia  and 
fibula,  and  which  binds  down  the  tibialis  posticus.  The  two 
preceding  muscles  take  part  of  their  origin  from  this  fascia. 

The  TIBIALIS  POSTICUS  (extensor  tarsi  tibialis)  lies  upon  the 
interosseojis  membrane,  between  the  two  bones  of  the  leg.  It 
arises  by  two  heads  from  the  adjacent  sides  of  the  tibia  and  fibula 
their  whole  length,  from  the  interosseous  membrane,  and  from  the 
aponeurosis  which  binds  it  in  its  place.  Its  tendon  passes  inwards 
beneath  the  tendon  of  the  flexor  longus  digitorum,  and  runs  in 
the  same  sheath  ;  it  then  passes  through  a  proper  sheath  over 


442 


THE   DISSECTOR. 


Fig.  135.  the  deltoid  ligament  and  beneath  the  cal- 

caneo-scaphoid  articulation  to  be  inserted 
into  the  tuberosity  of  the  scaphoid  and  inter- 
nal cuneiform  bone  ;  a  process  of  its  tendon 
being  prolonged  outwards  to  the  external 
cuneiform. 

The  student  will  observe  that  the  two  latter 
muscles  change  their  relative  position  to  each  other 
in  their  course.  Thus,  in  the  leg,  the  position  of 
the  three  muscles  from  within  outwards,  is  flexor 
longus  digitorum,  tibialis  posticus,  flexor  longus 
pollicis.  At  the  inner  malleolus,  the  relation  of 
the  tendons  is  tibialis  posticus,  flexor  longus  digi- 
torum, both  in  the  same  sheath ;  then  a  broad 
groove,  which  lodges  the  posterior  tibial  artery, 
venae  comites,  and  nerve ;  and  lastly,  the  flexor 
longus  pollicis. 

The  ARTERIES  of  the  posterior  tibial  region 
are  the  posterior  tibial  and  its  branches. 

The   POSTERIOR  TIBIAL   ARTERY  passes    ob- 

liquely  downwards  along  the  tibial  side  of  the 
leg  from  the  lower  border  of  the  popliteus 
muscle  to  the  concavity  of  the  os  calcis,  where 
it  divides  into  the  internal  and  external 
plantar  artery.  In  its  course,  it  rests  upon 
the  tibialis  posticus,  flexor  longus  digitorum, 
and  tibia,  and  is  covered  in  by  the  intermus- 
cular  fascia.  It  is  accompanied  by  venae 
comites,  and  the  posterior  tibial  nerve,  which 
lies  to  its  inner  side  above,  and  to  the  outer 
side  in  the  rest  of  its  course. 

Operation. — One  of  the  most  difficult  operations 

A  POSTERIOR  VIEW  OP  THE  LEG,  SHOWING  THE  POPLITEAL  AND  POSTERIOR 
TIBIAL  ARTERIES. — 1.  The  tendons  forming  the  inner  hamstring.  2.  The 
tendon  of  the  biceps  forming  the  outer  hamstring.  3.  The  popliteus  muscle.  4. 
The  flexor  longus  digitorum.  5.  The  tibialis  posticus.  6.  The  fibula  ;  imme- 
diately below  the  figure  is  the  origin  of  the  flexor  longus  pollicis  ;  the  muscle 
has  been  removed  in  order  to  expose  the  peroneal  artery.  7.  The  peronei 
muscles,  longus  and  brevis.  8.  The  lower  part  of  the  flexor  longus  pollicis 
muscle  with  its  tendon.  9.  The  popliteal  artery  giving  off  its  articular  and  mus- 
cular branches  ;  the  two  superior  articular  are  seen  in  the  upper  part  of  the  pop- 
liteal  space  passing  above  the  two  heads  of  the  gastrocnemius  muscle,  which  are 
cut  through  near  to  their  origin.  The  two  inferior  are  in  relation  with  the  pop- 
liteus muscle.  10.  The  anterior  tibial  artery  passing  through  the  angular  inter- 
space between  the  two  heads  of  the  tibialis  posticus  muscle.  11.  The  posterior 
tibial  artery.  12.  The  relative  position  of  the  tendons  and  artery  at  the  inner 
ankle  from  within  outwards,  previously  to  their  passing  beneath  the  internal 
annular  ligament.  13.  The  peroneal  artery,  dividing  into  two  branches ;  the 
anterior  peroneal  is  seen  piercing  the  interosseous  membrane.  14.  The  pos- 
terior peroneal. 


POSTERIOR  TIBIAL  ARTERY.  443 

in  the  entire  body  is  the  ligature  of  the  posterior  tibial  artery,  in  the 
upper  third  of  its  course.  It  is  happily  one  rarely  required,  excepting  in 
the  case  of  accidental  wound,  where  both  extremities  of  the  vessel  must 
be  secured.  An  incision,  four  or  five  inches  in  length,  is  made  parallel 
with  the  inner  border  of  the  tibia,  and  about  half  an  inch  distant.  This 
will  divide  the  integument,  superficial  fascia,  and  deep  fascia ;  the  border  of 
the  gastrocnemius  is  then  to  be  held  aside,  and  another  incision  of  the 
same  extent  made  through  the  soleus  down  to  the  intermuscular  fascia. 
When  the  intermuscular  fascia  is  clearly  exposed,  it  may  be  slit  up.  The 
artery,  with  its  venae  comites  and  nerve,  lie  immediately  beneath  it,  near 
the  middle  line  of  the  leg,  and  resting  upon  the  tibialis  posticus  muscle. 
The  nerve  lies  upon  the  artery,  or  directly  to  its  outer  side. 

In  the  middle  third  of  the  course  of  the  artery  a  longitudinal  incision 
two  inches  and  a  half  in  length  should  be  made  parallel  with  the  internal 
border  of  the  tibia  and  tendo  Achillis,  and  midway  between  them.  The 
integument,  superficial  and  deep  fascia  should  be  divided  and  the  sheath 
of  the  vessels  opened  upon  a  director.  The  artery  lies  between  the 
venae  comites,  and  the  nerve  is  to  the  outer  side. 

At  the  ankle,  an  incision  two  inches  in  length  is  sufficient.  It  must 
be  directed  obliquely  from  the  inner  border  of  the  tendo  Achillis,  to  the 
point  of  the  internal  malleolus,  or  in  the  opposite  direction,  as  may  be 
most  convenient.  It  will  divide  the  integument,  superficial  fascia,  and 
deep  fascia.  The  next  step,  in  the  living  subject,  would  be  to  feel  for  the 
pulsation  of  the  artery  ;  but.  in  the  dead,  the  student  will  find  the  sheath 
containing  the  vessels  at  about  three-quarters  of  an  inch  from  the  edge 
of  the  malleolus.  The  nerve  lies  to  the  outer  side  of  the  artery.  If  the 
student  open  a  sheath  lying  immediately  under  cover  of  the  malleolus, 
he  will  find  it  to  contain  the  tendons  of  the  flexor  longus  digitorum  and 
tibialis  posticus  muscles.  And  if  he  get  too  near  the  tendo  Achillis,  he 
will  open  the  sheath  of  the  tendon  of  the  flexor  longus  pollicis. 

The  branches  of  the  posterior  tibial  artery  are  the — 
Peroneal,  Internal  calcanean, 

Nutritious,  Internal  plantar, 

Muscular,  External  plantar. 

The  peroneal  artery  is  given  off  from  the  posterior  tibial  at 
about  two  inches  below  the  lower  border  of  the  popliteus  mus- 
cle; it  is  nearly  as  large  as  the  anterior  tibial  artery,  and  passes 
obliquely  outwards  to  the  fibula.  It  then  runs  downwards  along 
the  inner  border  of  the  fibula  to  its  lower  third,  where  it  divides 
into  the  anterior  and  posterior  peroneal  artery.  At  the  upper 
part  of  its  course  it  rests  upon  the  tibialis  posticus,  but  soon  gets 
under  cover  of  the  flexor  longus  pollicis,  having  the  fibula  to  its 
outer  side.  The  peroneal  artery,  previously  to  its  division,  gives 
off  muscular  branches  and  a  nutrient  branch  to  the  fibula. 

Operation. — From  the  very  deep  position  of  the  fibular  artery  beneath 
the  flexor  longus  pollicis  muscle,  and  behind  the  fibula,  this  is  a  very 
difficult  operation.  This  may  well  be  conceived,  when  it  is  recollected 
that  it  has  been  proposed  to  saw  away  a  portion  of  the  bone  to  reach  the 
artery.  Like  the  operation  on  the  upper  part  of  the  tibial  arteries,  it  is 
not  likely  to  be  required  except  in  the  case  of  accidental  wound.  The 
operation  is  performed  in  the  middle  third  of  the  leg,  previously  to  the 


444  THE   DISSECTOR. 

division  of  the  artery  into  the  anterior  and  posterior  peroneal.  An  inci- 
sion, four  inches  in  length,  must  be  made  parallel  with  and  at  about  an 
inch  distant  from  the  fibula.  The  integument,  superficial  and  deep 
fascia,  being  drawn  aside,  the  soleus  and  intermuscular  fascia  must  be 
divided  to  the  same  extent.  The  flexor  longus  pollicis  is  then  to  be 
separated  from  the  fibula,  and  drawn  outwards.  Beneath  this  muscle, 
by  the  side  of  the  fibula,  will  be  found  the  artery.  It  has  no  accompany- 
ing nerve. 

The  anterior  peroneal  artery,  at  the  lower  third  of  the  leg, 
pierces  the  interosseous  membrane,  and  is  distributed  on  the 
front  of  the  outer  malleolus,  anastomosing  with  the  external 
malleolar  and  tarsal  artery. 

The  posterior  peroneal  continues  onwards  along  the  posterior 
aspect  of  the  outer  malleolus  to  the  side  of  the  os  calcis,  to 
which,  and  to  the  muscles  arising  from  it,  it  distributes  external 
calcanean  branches.  It  anastomoses  with  the  anterior  peroneal, 
tarsal,  external  plantar,  and  posterior  tibial  artery — with  the 
latter  by  means  of  a  small  transverse  branch. 

The  nutritious  artery  of  the  tibia  arises  from  the  trunk  of  the 
tibial,  frequently  above  the  origin  of  the  peroneal,  and  proceeds 
to  the  nutritious  canal,  which  it  traverses  obliquely  from  below 
upwards. 

The  muscular  branches  of  the  posterior  tibial  artery  are  distri- 
buted to  the  soleus  and  deep  muscles  on  the  posterior  aspect  of 
the  leg.  One  branch  is  deserving  of  notice,  a  recurrent  branch, 
which  arises  from  the  posterior  tibial  above  the  origin  of  the 
peroneal  artery,  pierces  the  soleus,  and  is  distributed  upon  the 
inner  side  of  the  head  of  the  tibia,  anastomosing  with  the  inferior 
internal  articular. 

The  internal  calcanean  branches,  three  or  four  in  number,  pro- 
ceed from  the  posterior  tibial  artery  immediately  before  its  divi- 
sion ;  they  are  distributed  to  the  inner  side  of  the  os  calcis,  to 
the  integument,  and  to  the  muscles  which  arise  from  its  inner 
tuberosity,  and  anastomose  with  the  external  calcanean  branches 
of  the  posterior  peroneal,  and  with  all  the  neighboring  arteries. 

The  POSTERIOR  TIBIAL  VEINS  receive  the  veins  which  accom- 
pany the  numerous  branches  of  the  posterior  tibial  and  peroneal 
arteries,  and  terminate  in  the  popliteal  vein. 

The  POSTERIOR  TIBIAL  NERVE  is  continued  along  the  posterior 
aspect  of  the  leg  from  the  lower  border  of  the  popliteus  muscle  to 
the  posterior  part  of  the  inner  ankle,  where  it  divides  into  the 
internal  and  external  plantar  nerve.  In  the  upper  part  of  its 
course  it  lies  to  the  inner  side  of  the  posterior  tibial  artery ;  it 
then  becomes  placed  to  its  outer  side ;  in  the  lower  third  of  the 
leg  it  lies  parallel  with  the  inner  border  of  the  tendo  Achillis. 

The  branches  of  the  posterior  tibial  nerve  are  muscular  twigs 
to  the  deep  muscles  of  the  posterior  aspect  of  the  leg ;  the  branch 


SOLE   OF   THE   FOOT. 


445 


to  the  flexor  longns  pollicis  accompanies  the  fibular  artery;  one 
or  two  filaments  which  entwine  around  the  artery  and  then  termi- 
nate in  the  integument ;  and  a  plantar  cutaneous  branch  which  is 
distributed  to  the  integument  of  the  heel,  and  inner  border  of  the 
sole  of  the  foot. 

SOLE  OF  THE  FOOT. 

Dissection. — The  sole  of  the  foot  is  to  be  dissected  by  carrying  a  longi- 
tudinal incision  along  the  middle  of  the  foot  from  the  heel  to  the  base  of 
the  toes,  and  crossing  it  in  the  latter  situation  by  a  transverse  incision. 
The  integument  is  next  to  be  dissected  off  the  superficial  fascia,  so  as  to 


fog.  136. 


Fig.  137. 


THE  FIRST  LAYER  OP  MUSCLES  IN 
THE  SOLE  OF  THE  FOOT  ;  THIS  LAYER 
IS  EXPOSED  BY  THE  REMOVAL  OF  THE 
PLANTAR  FASCIA. — 1.  The  os  calcis. 
2.  The  posterior  part  of  the  plantar 
fascia  divided  transversely.  3.  The 
abductor  pollicis.  4.  The  abductor 
minimi  digiti.  5.  The  flexor  brevis 
digitorum.  6.  The  tendon  of  the 
flexor  longus  pollicis  muscle.  7,  7. 
The  lumbricales.  On  the  second  and 
third  toes,  the  tendons  of  the  flexor 
longus  digitorum  are  seen  passing 
through  the  bifurcation  of  the  tendons 
of  the  flexor  brevis  digitorum. 

38 


THE  THIRD  AND  A  PART  OF  THK 
SECOND  LAYER  OF  MUSCLES  OF  THE 
SOLE  OF  THE  FOOT. — 1.  The  divided 
edge  of  the  plantar  fascia.  2.  The 
musculus  accessorius.  3.  The  tendon 
of  the  flexor  longus  digitorum,  pre- 
viously to  its  division.  4.  The  tendon 
of  the  flexor  longus  pollicis.  5.  The 
flexor  brevis  pollicis.  6.  The  adductor 
pollicis.  7.  The  flexor  brevis  minimi 
digiti.  8.  The  transversus  pedis.  9. 
Interossei  muscles,  plantar  and  dorsal. 
10.  A  convex  ridge  formed  by  the 
tendon  of  the  peroneus  longus  muscle 
in  its  oblique  course  across  the  foot. 


446  THE   DISSECTOR. 

make  an  inner  and  an  outer  flap.     Each  of  the  toes  is  then  to  be  treated 
in  a  similar  manner,  being  laid  open  by  a  longitudinal  incision. 

The  SUPERFICIAL  FASCIA  is  closely  adherent  to  the  integument, 
and  must  be  raised  in  the  same  manner,  turning  the  flaps  to  either 
side.  In  so  doing,  the  cutaneous  nerve  of  the  sole  of  the  foot  is 
to  be  sought  for  near  the  heel ;  and  near  the  front  of  the  foot,  the 
digital  arteries  and  nerves  to  the  outer  sides  of  the  great  and  little 
toes.  When  turned  up  and  examined  on  its  under  surface,  the 
superficial  fascia  has  the  appearance  of  a  dense  cushion  of  fat 
held  down  at  numerous  points  by  strong  cellular  tissue. 

The  DEEP,  or  PLANTAR,  FASCIA  is  a  strong  aponenrotic  structure 
stretched  between  the  under  surface  of  the  tuberosities  of  the 
calcaneum  and  the  heads  of  the  metatarsal  bones.  It  thus  serves 
a  double  purpose,  being  mainly  instrumental  in  preserving  the 
convexity  of  the  arch  of  the  foot,  while  it  protects  from  injurious 
pressure  the  soft  parts  between  it  and  the  bones.  This  fascia  is 
divided  into  three  portions,  a  middle  and  two  lateral.  The  middle 
portion  is  very  dense,  and  is  made  up  of  strong  tendinous  fibres, 
closely  interlaced  with  each  other.  It  occupies  the  middle  of  the 
sole,  and  terminates  towards  the  toes  in  five  slips,  which  are  held 
firmly  together  by  transverse  bands  of  fibres  passing  between  and 
interlacing  them.  Each  of  the  slips  embraces  the  base  of  the 
corresponding  toe,  and  is  attached  in  the  middle  to  the  sheath  of 
the  flexor  tendons,  and  at  either  side  to  the  head  of  the  meta- 
tarsal bone.  Between  the  slips  at  their  base,  the  transverse  bands 
of  fibres  already  described  form  a  kind  of  arch  of  protection  to 
the  digital  vessels  and  nerves.  The  lateral  portions  of  the  plantar 
fascia  cover  in  the  muscles  of  the  borders  of  the  foot ;  the  inner 
portion  being  continuous  with  the  fascia  of  the  dorsum  of  the 
foot,  and  the  outer  one  attached  to  the  os  calcis  and  base  of  the 
metatarsal  bone  of  the  little  toe.  Between  these  latter  points 
the  fascia  forms  a  thick  band,  which  gives  origin  to  a  part  of  the 
abductor  minimi  digiti  muscle.  At  the  junction  of  the  middle 
with  the  lateral  portions  of  the  fascia  lata,  two  septa  are  sent 
inwards,  which  separate  the  three  superficial  muscles,  and  form  a 
complete  sheath  for  the  middle  muscle,  the  flexor  brevis  digitorum. 
The  lateral  portions  of  the  plantar  fascia  are  easily  removed 
from  the  muscles.  The  middle  portion  must  be  divided  through 
its  middle,  and  each  extremity  raised  separately ;  the  anterior 
towards  the  toes,  from  which  it  may  be  divided ;  the  posterior 
towards  the  os  calcis  :  this  latter  dissection  cannot,  however,  be 
effected  without  dividing  many  of  the  muscular  fibres  of  the  flexor 
brevis  digitorum,  which  arise  from  the  surface  of  the  fascia. 
When  the  fascia  is  removed  the  lateral  septa  may  be  seen,  together 
with  two  digital  nerves  which  perforate  the  septa,  and  the  tendon 
of  the  flexor  longus  pollicis. 


SOLE  OP  THE  FOOT.  447 

The  MUSCLES  of  the  sole  of  the  foot  may  be  arranged  in  four 
layers:  — 

First  Layer. 

Abductor  poll  ids,  Flexor  brevis  digitorum. 

Abductor  minimi  digiti, 

Second  Layer. 

Tendon  of  the  flexor  longus  pollicis,       Accessorins, 
Tendons  of  the  flexor  longus  digitorum,  Luinbricales. 

Third  Layer. 

Flexor  brevis  pollicis,         Flexor  brevis  minimi  digiti, 
Adductor  pollicis,  Transversus  pedis. 

Fourth  Layer. 
Three  plantar  interossei  (all  adductors). 

The  ABDUCTOR  POLLICIS  lies  along  the  inner  border  of  the  foot  ; 
it  arises  by  two  heads,  between  which  the  tendons  of  the  long 
flexors,  arteries,  veins,  and  nerves  enter  the  sole  of  the  foot.  One 
head  arises  from  the  inner  tuberosity  of  the  os  calcis,  the  other 
from  the  internal  annular  ligament  and  plantar  fascia.  Insertion, 
into  the  base  of  the  first  phalanx  of  the  great  toe,  and  internal 
sesamoid  bone. 

The  ABDUCTOR  MINIMI  DIGITI  lies  along  the  outer  border  of  the 
sole  of  the  foot.  It  arises  from  the  outer  tuberosity  of  the  os 
calcis,  and  from  the  plantar  fascia,  as  far  forward  as  the  base  of 
the  metatarsal  bone  of  the  little  toe,  and  is  inserted  into  the  base 
of  the  first  phalanx  of  the  little  toe. 

The  FLEXOR  BREVIS  DIGITORUM  (pcrforatus)  is  placed  between 
the  two  preceding  muscles.  It  arises  from  the  under  surface  of 
the  os  calcis,  plantar  fascia,  and  intermuscular  septa,  and  is  inserted 
by  four  tendons  into  the  base  of  the  second  phalanx  of  the  four 
lesser  toes.  Each  tendon  divides,  previously  to  its  insertion,  to 
give  passage  to  the  tendon  of  the  long  flexor  ;  hence  its  cognomen 


l>  ^section.  —  These  muscles  are  to  be  divided  posteriorly  from  their 
origin,  and  anteriorly  through  their  tendons,  and  removed.  This  will 
bring  into  view  the  second  layer,  and  the  external  plantar  artery  and 
nerve,  which  lie  obliquely  across  it.  At  the  point  where  the  tendons  of 
the  long  flexors  cross  each  other,  a  communicating  slip  is  sent  between 
them,  which  associates  their  action. 

The  MUSCULUS  ACCESSORIUS  arises  by  two  slips  from  either  side 
of  the  under  surface  of  the  os  calcis  ;  the  inner  slip  being  fleshy, 
the  outer  tendinous  and  blended  with  the  ligamentum  longum 
plantai.  It  is  inserted  into  the  outer  side  and  upper  surface  of 
the  tendon  of  the  flexor  longus  digitorum. 

The  LUMBRICALES  (lumbricus,  an  earthworm)  are  four  little 
muscles  arising  from  the  tendons  of  the  flexor  longus  digitorum 


448  THE   DISSECTOR. 

at  their  point  of  bifurcation,  and  inserted  into  the  expansion  of 
the  extensor  tendons,  and  into  the  base  of  the  first  phalanx  of 
the  four  lesser  toes  on  their  tibial  side.  The  innermost  lumbri- 
calis  is  connected  with  only  one  tendon. 

Dissection. — To  expose  the  third  layer  of  muscle  without  disturbing 
the  vessels,  cut  the  tendons  of  the  long  flexors  across  through  the  inser- 
tion of  the  accessorius,  draw  that  muscle  with  the  tendons  backwards  by 
means  of  hooks,  and  snip  off  the  digital  extremities  of  the  tendons.  A 
little  cleaning  of  fat  and  cellular  tissue  will  then  bring  clearly  into  view 
the  third  layer  of  muscles.  In  this  dissection  the  branches  of  the  in- 
ternal plantar  nerve  will  run  considerable  risk,  unless  the  student  be 
careful. 

The  FLEXOR  BREVIS  POLLICIS  arises  by  a  pointed  tendinous 
process  from  the  side  of  the  cuboid,  the  external  cuneiform  bone, 
and  the  expanded  tendon  of  the  tibialisposticus;  itisinsertedbj  two 
heads  into  the  base  of  the  first  phalanx  of  the  great  toe,  the  inner 
head  being  conjoined  with  the  insertion  of  the  adductor  pollicis, 
the  outer  head  with  the  adductor  pollicis  and  transversus  pedis. 
Two  sesamoid  bones  are  developed  in  the  tendons  of  insertion  of 
these  two  heads,  and  the  tendon  of  the  flexor  longus  pollicis  lies 
in  the  groove  between  them. 

The  ADDUCTOR  POLLICIS  arises  from  the  cuboid  bone,  from  the 
sheath  of  the  tendon  of  the  peroneus  longus,  and  from  the  base 
of  the  third  and  fourth  metatarsal  bones.  It  is  inserted  into  the 
base  of  the  first  phalanx  of  the  great  toe,  in  conjunction  with  the 
outer  head  of  the  flexor  brevis  pollicis. 

The  FLEXOR  BREVIS  MINIMI  DIGITI  arises  from  the  base  of  the 
metatarsal  bone  of  the  little  toe,  and  from  the  sheath  of  the  ten- 
don of  the  peroneus  longus.  It  is  inserted  into  the  base  of  the 
first  phalanx  of  the  little  toe,  on  its  outer  side. 

The  TRANSVERSUS  PEDIS  arises  by  fleshy  slips  from  the  heads 
of  the  metatarsal  bones  of  the  four  lesser  toes.  Its  tendon  is  in- 
serted into  the  base  of  the  first  phalanx  of  the  great  toe,  being 
blended  with  that  of  the  adductor  pollicis. 

The  plantar  interossei  muscles  (page  450),  must  be  left  until  the  arte- 
ries and  nerves  have  been  dissected  and  studied. 

ACTIONS. — The  actions  of  the  muscles  in  the  sole  of  the  foot  are  implied 
in  their  names.  See  analysis  (page  451). 

The  ARTERIES  of  the  sole  of  the  foot  are  the  internal  and  ex- 
ternal plantar,  the  terminal  branches  of  the  posterior  tibial  artery 
at  the  inner  malleolus.  Their  distribution  maybe  thus  expressed 
in  a  tabular  form  : — 

internal  plantar   f  milscular 
articular 
Posterior    tibial       externalplantar 


posterior  perforating. 


NERVES  OP   SOLE  OP  FOOT. 


449 


Fig.  138. 


The  INTERNAL  PLANTAR  ARTERY  passes  along  the  inner  border 
of  the  foot  beneath  the  abductor  pollicis,  and  distributes  branches 
to  the  inner  border  of  the  foot  and  great  toe. 

The  EXTERNAL  PLANTAR  ARTERY,  much  larger  than  the  inter- 
nal, passes  obliquely  outwards  between  the  first  and  second 
layers  of  the  plantar  muscles,  to  the  fifth  metatarsal  space.  It 
then  turns  horizontally  inwards  between  the  second  and  third 
layers,  to  the  first  metatarsal  space,  where  it  inosculates  with  the 
dorsalis  pedis.  The  horizontal  portion  of  the  artery  describes  a 
slight  curve,  having  the  convexity  forwards  ;  this  is  the  plantar 
arch. 

The  muscular  and  articular  branches  of  the  external  plantar 
artery  are  distributed  to  the  muscles  in  the  sole  of  the  foot  and 
to  the  articulations  of  the  tarsus. 

The  digital  branches  are  four  in  number ;  the  first  is  distri- 
buted to  the  outer  side  of  the  little  toe  ;  the  three  others  pass 
forwards  to  the  cleft  between  the  toes, 
and  divide  into  collateral  branches,  which 
supply  the  adjacent  sides  of  the  three  ex- 
ternal to«s,  and  the  outer  side  of  the  second. 
At  the  bifurcation  of  the  toes,  a  small 
branch  is  sent  upwards  from  each  digital 
artery,  to  inosculate  with  the  interosseous 
branches  of  the  metatarsea  ;  these  are  the 
anterior  perforating  arteries. 

The  posterior  perforating  are  three 
small  branches  which  pass  upwards  be- 
tween the  heads  of  the  three  external 
dorsal  interossei  muscles,  to  inosculate 
with  the  arch  formed  by  the  metatarsea 
artery. 

The  NERVES  of  the  sole  of  the  foot  are, 
like  the  arteries,  the  internal  and  external 
plantar  (Fig.  132,  12),  terminal  branches 
of  the  posterior  tibiaf. 

The  INTERNAL  PLANTAR  NERVE,  larger 
than  the  external,  crosses  the  posterior 
tibial  vessels  to  enter  the  sole  of  the 
foot,  and  becomes  placed  between  the 

THE  ARTERIES  OP  THE  SOLE  OF  THE  FOOT  ;  THE  FIRST  AND  A  PART  OF  THE 
SECOND  LAYER  OF  MUSCLES  HAVING  BEEN  REMOVED. — 1.  The  under  and 
posterior  part  of  the  os  calcis ;  to  which  the  origins  of  the  first  layer  of  muscles 
remain  attached.  2.  The  rausculus  accessorius.  3.  The  long  flexor  tendons. 
4.  The  tendon  of  the  peroneus  longus.  5.  The  termination  of  the  posterior 
tihial  artery.  6.  The  internal  plantar.  7.  The  external  plantar  artery.  8. 
The  plantar  arch  giving  off  four  digital  branches,  which  pass  forwards  on  the 
interossei  muscles  to  divide  into  collateral  branches. 

38* 


450  THE   DISSECTOR. 

abductor  pollicis  and  flexor  brevis  digitorum ;  it  then  enters 
the  sheath  of  the  latter  muscle,  and  divides  opposite  the  bases 
of  the  metatarsal  bones  into  three  digital  branches;  one  to 
supply  the  adjacent  sides  of  the  great  and  second  toe ;  the 
second  the  adjacent  sides  of  the  second  and  third  toe ;  and  the 
third  the  corresponding  sides  of  the  third  and  fourth  toe.  This 
distribution  is  precisely  similar  to  that  of  the  digital  branches 
of  the  median  nerve. 

In  its  course  the  internal  plantar  nerve  gives  off  cutaneous 
branches  to  the  integument  of  the  inner  side  and  sole  of  the  foot ; 
muscular  branches ;  a  digital  branch  to  the  inner  border  of  the 
great  toe  ;  and  articular  branches  to  the  articulations  of  the  tarsal 
and  metatarsal  bones. 

The  EXTERNAL  PLANTAR  NERVE,  the  smaller  of  the  two,  follows 
the  course  of  the  external  plantar  artery  to  the  outer  border  of 
the  musculus  accessorius,  beneath  which  it  sends  several  deep 
branches  to  supply  the  adductor  pollicis,  interossei,  transversus 
pedis  and  the  articulations  of  the  tarsal  and  metatarsal  bones. 
It  then  gives  branches  to  the  integument  of  the  outer  border  and 
sole  of  the  foot,  and  sends  forward  two  digital  branches  to  supply 
the  little  toe  and  half  the  next. 

When  the  arteries  and  nerves  have  been  examined,  the  transversus 
pedis  and  other  muscles  may  be  removed  which  impede  the  view  of  the 
plantar  interossei.  They  are  covered  in  by  a  thin  aponeurotic  fascia 
which  is  attached  in  front  to  a  ligamentous  band  passing  between  the 
heads  of  the  metatarsal  bones,  the  transverse  ligament.  This  ligament  as 
well  as  the  fascia  must  be  divided  in  order  to  bring  the  full  extent  of  the 
interossei  into  view. 

The  PLANTAR  INTEROSSEI  muscles  are  three  in  number,  and  are 
placed  upon  rather  than  between  the  metatarsal  bones.  They 
arise  from  the  base  of  the  metatarsal  bones  of  the  three  outer 
toes,  and  are  inserted  into  the  inner  side  of  the  extensor  tendon 
and  base  of  the  first  phalanx  of  the  same  toes.  In  their  action 
they  are  all  adductors. 

When  the  anatomy  of  the  muscles,  vessels,  and  nerves  of  the  sole  of 
the  foot  is  completed,  and  the  student  is  preparing  to  study  the  ligaments, 
he  should  lay  open  the  groove  in  the  cuboid  bone  by  dividing  the  liga- 
mentous sheath  in  which  it  is  contained,  and  expose  the  tendon  of  the 
peroneus  longus  in  its  passage  across  the  foot,  to  its  insertion  into  the 
base  of  the  metatarsal  bone  of  the  great  toe.  In  that  portion  of  the  ten- 
don which  lies  in  contact  with  the  cuboid,  he  will  find  a  sesamoid  bone. 
In  some  instances  the  deposit  of  bone  has  not  taken  place,  and  the  thick- 
ening of  the  tendon  is  merely  fibro-cartilaginous.  The  insertion  of  the 
tendon  of  the  tibialis  posticus  may  also  be  examined  at  the  same  time 
with  advantage. 


MUSCLES  OF  THE  LOWER  EXTREMITY.  451 

Analysis  of  the  Arrangement  and  Actions  of  the  Muscles  of  the 
lower  Extremity. 

The  lower  extremity  is  composed  of,  1st,  the  femur ;  2d,  the 
tibia  and  fibula ;  3d,  the  tarsus  ;  4th,  the  toes.  The  trunk  is  the 
fixed  point  from  which  arise  the  muscles  that  move  the  thigh. 
The-  articulation  of  the  hip  is  a  universal  joint ;  hence  the  move- 
ments are  very  numerous,  but  they  may  all  be  referred  to  the  four 
primary  directions,  forwards,  backwards,  inwards,  outwards,  to 
which  is  added  rotation  on  its  axis. 

The  articulation  of  the  femur  with  the  tibia  is  a  hinge  joint, 
and  is  therefore  applicable  only  to  flexion  and  extension :  the 
muscles  performing  these  actions  arise  from  the  pelvis  and  femur. 
But  as  we  descend,  we  find  the  length  of  the  bones  diminishing 
while  their  numbers  increase.  The  foot  is  a  compound  organ 
made  up  of  a  number  of  parts,  each  part  performing  distinct 
movements.  We  are  therefore  prepared  to  find  a  number  of 
muscles  destined  to  supply  these  demands.  But  numerous  as 
they  really  are,  they  may,  by  a  careful  analysis,  be  arranged  and 
grouped  under  a  few  simple  actions. 

The  movements  of  the  tarsus  may  be  referred  to  four  heads, 
flexion,  extension,  adduction,  abduction,  the  two  latter  actions 
being  very  imperfect.  The  muscles  performing  these  movements 
are  the  following : — 

Flexion.  Extension. 

Tibialis  anticus,  Tibialis  posticus, 

Peroueus  tertius.  Peroneus  longus, 

brevis,  and   where 

forcible  action  is  required, 
as  in  walking, 
Gastrocnemius, 
Plantaris, 
Soleus. 

Adduction.  Abduction. 
Tibialis  anticus,                                  Peroneus  longus, 
posticus.                                            -  brevis. 

The  movements  of  the  toes  may  in  the  same  manner  be  reduced 
to  precisely  the  same  simplicity  of  action,  thus  : — 

Flexion.  Extension. 

Flexor  longus  digitorum,  Extensor  longus  digitorum, 

• brevis  digitorum,  — brevis  digitorum. 

accessorius, 

• minimi  digiti. 


452  THE  DISSECTOR. 

Adduction.  Abduction. 

dorsal-  Interossei,  3  dorsal. 

3  plantar.  Abductor  minimi  digiti. 

The  great  toe,  like  the  thumb  in  the  hand,  enjoys  an  inde- 
pendence of  action,  and  is  therefore  provided  with  distinct  mus- 
cles to  perform  its  movements.  But  even  here  the  direction  of 
the  actions  is  nothing  more  than  is  possessed  by  each  of  the  other 
toes,  and  may  be  referred  to  the  same  plan,  thus — 

Flexion.  Extension. 

Flexor  longus  pollicis,                    Extensor  proprius  pollicis, 
. brevis  pollicis.  brevis  digitorum. 

Adduction.  Abduction. 

Adductor  pollicis.  Abductor  pollicis. 

The  only  muscles  excluded  from  this  table  are  the  lumbricales, 
four  small  muscles,  which,  from  their  attachments  to  the  tendons 
of  the  long  flexor,  appear  to  be  assistants  to  their  action ;  and 
the  transversus  pedis,  a  small  muscle  placed  transversely  in  the 
foot  across  the  heads  of  the  metatarsal  bones,  which  has  for  its 
office  the  drawing  together  of  the  toes. 


CHAPTER    IX. 

PELVIS  AND  ORGANS  OF  GENERATION. 

THE  cavity  of  the  pelvis  is  that  portion  of  the  great  abdominal 
cavity  which  is  included  within  the  bones  of  the  pelvis  below 
the  level  of  the  linea  ilio-pectinea  and  the  promontory  of  the 
sacrum.  It  is  bounded  by  the  cavity  of  the  abdomen  above, 
and  by  the  perineum  below.  Its  internal  parietes  are  formed  in 
front,  below,  and  at  the  sides,  by  the  peritoneum,  pelvic  fascia, 
levatores  ani  and  obturator  muscles ;  and  behind  by  the  coccygei 
muscles,  sacro-ischiatic  ligaments,  pyriformis  muscle,  sacral  plexus 
of  nerves,  sacrum,  and  coccyx. 

The  VISCERA  of  the  pelvis  in  the  male,  are  the  urinary  bladder, 
vesiculae  seminales,  prostate  gland,  and  rectum ;  and  in  the  female, 
the  urinary  bladder,  uterus,  vagina,  and  rectum. 

Yiewed  from  above,  the  urinary  bladder  will  be  seen  to  form  a 
convexity,  pointed  in  the  male,  more  obtuse  in  the  female,  behind 
the  ossa  pubis ;  the  rectum,  flexuous  in  its  course,  rests  against 
the  sacrum.  In  the  male,  the  bladder  and  rectum  are  in  contact ; 


THE  PELVIS. 


453 


in  the  female,  the  uterus  is  interposed,  and  with  its  broad  liga- 
ments stretching  out  on  each  side  forms  a  transverse  septum, 
which  divides  the  cavity  of  the  pelvis  into  an  anterior  and  a 
posterior  part. 

The  peritoneum  invests  the  pelvic  viscera  only  partially ;  thus 

Fig.  139. 


A  SIDE  VIEW  OF  THE  VISCERA  OF  THE  MALE  PELVIS  IN  SITU.  THE  RIGHT 
SIDE  OF  THE  PELVIS  HAS  BEEN  REMOVED  BY  A  VERTICAL  SECTION  MADE 
THHOUGH  THE  OS  PUBIS,  NEAR  TO  THE  SYMPHYSIS  .'  AND  ANOTHER  THROUGH 
THE  MIDDLE  OF  THE  SACRUM. — 1.  The  divided  surface  of  the  os  pubis.  2.  The 
divided  surface  of  the  sacrum.  3.  The  body  of  the  bladder.  4.  Its  fundus  ; 
from  the  apex  is  seen  passing  upwards  the  urachus.  5.  The  base  of  the  bladder. 
6.  The  ureter.  7.  The  neck  of  the  bladder.  8,  8.  The  pelvic  fascia;  the  fibres 
immediately  above  7  are  given  off  from  the  pelvic  fascia,  and  represent  the 
anterior  ligaments  of  the  bladder.  9.  The  prostate  gland.  10.  The  mem- 
branous portion  of  the  urethra,  between  the  two  layers  of  the  deep  perineal 
fascia.  11.  The  deep  perineal  fascia  formed  of  two  layers.  12.  One  of  Cowper's 
glands  between  the  two  layers  of  deep  perineal  fascia,  and  beneath  the  mem- 
branous portion  of  the  urethra.  13.  The  bulb  of  the  corpus  spongiosum.  14. 
The  body  of  the  corpus  spongiosum.  15.  The  right  crus  penis.  16.  The  upper 
part  of  the  first  portion  of  the  rectum.  17.  The  recto-vesical  fold  of  peritoneum. 
18.  The  second  portion  of  the  rectum.  19.  The  right  vesicula  seminalis.  20. 
The  vas  deferens.  21.  The  rectum  covered  with  the  descending  layer  of  the 
pelvic  fascia,  just  aa  it  is  making  its  bend  backwards  to  constitute  the  third 
portion.  22.  A  part  of  the  levator  ani  muscle  investing  the  lower  part  of  the 
rectum.  23.  The  external  sphincter  ani.  24.  The  interval  between  the  deep 
and  superficial  perineal  fascia ;  they  are  seen  to  be  continuous  beneath  the 
figure. 

it  forms  a  complete  covering  for  the  upper  portion  of  the  rectum, 
and  connects  it  by  a  duplicature  (mesorectum)  to  the  surface 
of  the  sacrum ;  lower  down  it  covers  only  the  anterior  surface  of 
the  rectum,  and  is  reflected  from  it  upon  the  posterior  surface 


454  THE  DISSECTOR. 

of  the  bladder.  The  fold  or  pouch,  formed  between  the  rectum 
and  the  bladder,  is  the  recto-vesical.  In  the  female,  the  pouch 
intervenes  between  the  rectum  and  the  vagina,  and  is  the  recto- 
vaginal;  and  a  second  pouch  is  formed  between  the  uterus  and 
bladder,  the  utero-vesical  fold.  From  the  sides  of  the  bladder 
the  peritoneum  ascends  upon  the  walls  of  the  pelvis,  and  its  re- 
flection from  the  sides  of  the  organ  to  the  pelvis  have  been  named 
false  ligaments  of  the  bladder. 

The  PELVIC  FASCIA  is  an  aponeurotic  layer  situated  beneath 
the  peritoneum,  forming  a  covering  to  the  walls  of  the  pelvis, 
and  reflected  from  its  walls  upon  the  viscera.  The  pelvic  fascia 
is  attached  to  the  internal  surface  of  the  ossa  pubis  near  the 
symphysis,  to  the  body  of  the  pubes  above  the  origin  of  the  ob- 
turator internus  muscle,  to  the  ilio-pectineal  line  of  the  brim  of 
the  pelvis  as  far  back  as  the  sacro-iliac  articulation,  and  to  the 
margin  of  the  great  sacro-ischiatic  foramen.  Having  descended 
upon  the  wall  of  the  pelvis  as  low  as  the  pubic  arch  in  front, 
and  the  spine  of  the  ischium  behind,  it  divides,  in  the  direction 
of  a  line  drawn  between  those  points,  into  two  layers,  internal 
and  external.  The  internal  layer  (recto-vesical),  is  continued 
downwards  to  the  prostate  gland,  neck  of  the  bladder  (vagina), 
and  rectum,  to  which  it  is  closely  attached;  and  is  reflected  for  a 
short  distance  upwards  and  downwards  on  these  viscera.  This 
layer  is  in  contact,  by  its  external  surface,  with  the  levator  ani 
muscle  and  coccygeus;  and  is  prolonged  backwards  over  the 
sacral  nerves  to  the  lower  part  of  the  sacrum  and  the  coccyx,  to 
which  it  is  attached,  meeting  on  the  middle  line  the  layer  of  the 
opposite  side.  The  external  layer  is  the  obturator  fascia,  it 
covers  in  the  obturator  muscle,  and  is  attached  to  the  ramus  of 
the  pubes  and  ischium  in  front,  and  to  the  tuberosity  of  the 
ischium  and  falciform  border  of  the  great  sacro-ischiatic  liga- 
ment below.  The  levator  ani  arises  from  the  line  of  division  of 
the  two  preceding  layers,  and  the  obturator  layer  sends  off  a  thin 
aponeurotic  expansion  which  covers  the  external  surface  of  that 
muscle.  The  obturator  fascia,  together  with  this  aponeurotic 
expansion,  constitute  the  ischio-rectal  fascia,  which  lines  the 
ischio-rectal  fossa,  and  is  attached  in  front  to  the  triangular  liga- 
ment of  the  perineum. 

The  anterior  part  of  the  pelvic  fascia  is  separated  from  its 
fellow  of  the  opposite  side  by  a  narrow  interval,  and  the  fascia 
passing  from  the  side  of  the  symphysis  to  the  upper  part  of  the 
prostate  gland  and  front  of  the  neck  of  the  bladder,  constitutes 
the  anterior  true  ligament  of  the  bladder  (pubio-vesical)  ;  a  little 
further  outwards,  the  fascia  passing  to  the  side  of  the  neck  of 
the  bladder,  constitutes  its  lateral  true  ligament;  and  reflected 
forwards  from  the  neck  of  the  bladder  upon  the  prostate, 


MUSCLES  OF  THE  PELVIS.  455 

it  forms  a  sheath  for  that  gland  which  incloses  the  prostatic 
plexus  of  veins.  Upon  the  rectum  and  vagina  it  also  forms  a 
sheath. 

The  student  must  now  turn  his  attention  to  the  study  of  the  viscera 
of  the  pelvis  ;  therefore,  after  examining  their  relative  position  from  above, 
he  should  proceed  to  separate  the  os  innominatum  of  the  left  side,  so  as 
to  obtain  a  side  view  of  these  organs.  For  this  purpose  he  must  divide 
the  pubes  with  the  saw  on  the  left  side,  a  little  external  to  the  symphysis. 
Then  let  him  cut  through  the  psoas  muscle  and  iliac  vessels  opposite  the 
sacro-iliac  symphysis,  and  divide  the  ligaments  of  that  articulation.  Next 
cut  away  with  the  scalpel  the  structures  adhering  to  the  inner  surface  of 
the  pubes  and  ilium  of  the  same  side  ;  taking  care  to  separate  the  pelvio 
fascia  from  its  connections  and  from  the  surface  of  the  obturator  muscle ; 
then  snip  across  the  spine  of  the  ischium,  so  as  to  leave  the  attachments 
of  the  levator  ani,  coccygeus,  and  lesser  sacro-ischiatic  ligament ;  and 
after  cutting  through  the  pyriformis  muscle,  remove  the  bone  altogether. 

The  MUSCLES  brought  into  view  by  this  dissection  are  the  coc- 
cygeus and  levator  ani. 

The  COCCYGEUS  muscle  is  a  thin  triangular  muscle.  It  arises 
from  the  spine  of  the  ischium  and  lesser  sacro-ischiatic  ligament, 
and  spreads  out  to  be  inserted  into  the  side  of  the  coccyx  and  lower 
part  of  the  sacrum.  The  coccygeus  rests  upon  the  lesser  sacro- 
ischiatic  ligament,  and  is  in  relation,  by  its  posterior  border,  with 
the  pyriforrais ;  and  by  the  anterior,  with  the  levator  ani. 

The  LEVATOR  ANI  is  a  thin  muscle,  situated  between  the  two 
layers  (recto-vesical  and  obturator)  of  the  pelvic  fascia,  and 
forming,  with  its  fellow  of  the  opposite  side,  a  movable  boundary 
to  the  outlet  of  the  pelvis.  It  arises  from  the  inner  surface  of  the 
os  pubis,  near  the  pubic  arch,  from  the  base  and  upper  border  of 
the  spine  of  the  ischium,  and  between  these  points  from  a  tendinous 
arch,  which  occupies  the  line  of  division  of  the  pelvic  fascia.  Its 
fibres  descend,  to  be  inserted  into  its  fellow  of  the  opposite  side 
beneath  the  prostate  gland,  into  the  rectum,  and  behind  the  rec- 
tum, into  its  fellow  of  the  opposite  side  and  the  side  of  the  ex- 
tremity of  the  coccyx. 

The  anterior  and  posterior  borders  of  the  levator  ani  are  thicker 
than  the  rest  of  the  muscle,  from  the  larger  extent  of  origin  of  the 
muscular  fibres;  the  anterior  border  arising  in  part  from  the 
ramus  of  the  pubes,  and  the  posterior  from  the  posterior  border 
of  the  spine  of  the  ischium.  The  anterior  border  of  the  two 
muscles  is  separated  by  a  space  which  gives  passage  to  the  urethra, 
and  in  the  female,  to  the  vagina.  This  space  is  closed  within  the 
pelvis  by  the  pelvic  fascia  and  anterior  ligaments  of  the  bladder. 
The  anterior  portion  of  the  muscle  forms  a  loop  beneath  the 
prostate  gland  with  the  corresponding  portion  of  the  opposite 
side ;  and  this  portion  has  been  described  under  the  names  of 
levator  or  compressor  prostate. 


456  THE   DISSECTOR. 

The  ACTION  of  the  coccygeus  muscle  is  to  flex  the  coccyx ;  that  of  the 
levator  ani,  to  lift  the  prostate  gland,  lower  part  of  the  anus  and  coccyx, 
and  thus  contract  the  space  of  the  outlet  of  the  pelvis.  The  levatores 
ani  are  antagonistic  of  the  diaphragm  and  the  rest  of  the  expulsory  mus- 
cles, and  serve  to  support  the  rectum  and  vagina  during  their  expulsive 
efforts.  The  levator  ani  acts  in  unison  with  the  diaphragm,  and  rises 
and  falls  like  that  muscle  in  forcible  respiration.  Yielding  to  the  pro- 
pulsive action  of  the  abdominal  muscles,  it  enables  the  outlet  of  the  pelvis 
to  bear  a  greater  force  than  a  resisting  structure,  and  on  the  remission  of 
such  action  it  restores  the  perineum  to  its  original  form. 

When  the  coccygeus  and  levator  ani  muscle  are  removed,  the  recto- 
vesical  layer  of  the  pelvic  fascia  may  be  traced  to  its  attachments  to  the 
neck  of  the  bladder  and  rectum,  and  over  the  prostate  gland,  to  which 
it  forms  a  sheath. 

The  recto-vesical  fascia  may  now  be  turned  down,  and  the  cellular 
tissue  and  fat  removed  from  the  side  of  the  bladder,  recto-vesical  pouch 
of  the  peritoneum  and  rectum.  The  dissection  may  be  facilitated  by 
blowing  air  into  the  bladder,  and  placing  a  little  cotton  wool  in  the  recto- 
vesical  pouch  of  the  peritoneum,  and  also  into  the  rectum  ;  but  care  should 
be  taken  to  avoid  over  distension  of  these  parts  ;  it  would  be  better  to  leave 
them  flaccid  than  to  stretch  their  coats.  In  the  progress  of  this  dissec- 
tion the  remains  of  the  hypogastric  artery  should  be  followed  forwards 
to  the  abdominal  parietes,  and  the  ureter  to  the  side  of  the  bladder ;  the 
vas  deferens  should  also  be  traced  downwards  behind  the  vesicula  semi- 
nalis  to  the  base  of  the  prostate. 

The  RECTUM. — The  rectum,  between  seven  and  eight  inches  in 
length,  commences  at  the  sacro-iliac  symphysis  on  the  left  side, 
and  terminates  at  the  anus.  It  is  divided  anatomically  into  three 
portions,  upper,  middle,  and  lower.  The  upper  portion,  com- 
prising half  its  length,  is  completely  surrounded  by  the  perito- 
neum, which  connects  it  to  the  wall  of  the  pelvis  by  means  of  the 
mesorectum.  It  is  in  relation  with  the  left  internal  iliac  vessels, 
ureter,  and  sacral  plexus  of  nerves.  The  middle  portion,  three 
inches  in  length,  and  extending  from  opposite  the  middle  of  the 
sacrum  to  the  tip  of  the  coccyx,  is  covered  by  peritoneum  only 
in  front  and  for  two-thirds  of  its  extent.  It  is  in  relation  behind 
with  the  sacrum  and  coccyx,  and  in  front  with  the  vesiculse  semi- 
nales,  the  triangular  portion  of  the  bladder  situated  between  those 
organs,  and  the  prostate  gland.  The  lower  portion,  an  inch  and 
a  half  in  length,  curves  backwards  from  the  prostate  gland  oppo- 
site the  tip  of  the  coccyx,  to  the  anus.  This  portion  is  more  or 
less  dilated,  and  is  supported  by  the  levatores  ani. 

URINARY  BLADDER. 

The  urinary  bladder  is  a  hollow  membranous  viscus,  triangular 
and  flattened  against  the  pubes  when  empty,  ovoid  when  distended, 
situated  behind  the  pubes  and  in  front  of  and  upon  the  rectum. 
It  is  larger  in  its  vertical  diameter  than  from  side  to  side,  and  its 
long  axis  is  directed  from  above  obliquely  downwards  and  back- 
wards. 


URINARY  BLADDER. 


457 


The  bladder  is  divided  into  body,  fundus,  base,  and  neck.  The 
body  comprehends  the  middle  zone  of  the  organ  ;  i\\z  fundus  (su- 
perior fundus),  its  upper  segment ;  the  base  (inferior  fundus)  the 
lower  broad  extremity  which  rests  on  the  rectum ;  and  the  neck, 
the  narrow  constricted  portion  which  is  applied  against  the  pros- 
tate gland. 

It  is  retained  in  position  by  ligaments,  which  are  divisible  into 
true  and  false.  The  true  ligaments  are  five  in  number,  two  an- 
terior, two  lateral,  and  the  cord  of  the  urachus.  The  false  liga- 
ments are  folds  of  the  peritoneum,  and  are  also  five  in  number, 
two  posterior,  two  lateral,  and  one  superior.  The  anterior  liga- 
ments are  formed  by  the  recto-vesical  fascia  in  its  passage  from 
the  inner  surface  of  the  pubes  on  each  side  of  the  symphysis  to 
the  neck  of  the  bladder  and  prostate  gland. 

The  lateral  ligaments  are  also  formed  by  the  recto-vesical  fascia 
in  its  passage  from  the  levatores  ani  muscles  to  the  sides  of  the 
prostate  gland  and  neck  of  the  bladder. 

The  ligament  of  the  urachus  is  a  fibrous  cord  resulting  from  the 
obliteration  of  a  tubular  canal  (urachus)  existing  in  the  embryo. 

Fig.  140. 


THE  PELVIC  VISCERA  OP  THE  MALE  SEEN  ON  THE  LEFT  SIDE. — 1.  The  body 
of  the  left  pubes  sawed  through.  2.  Corpus  cavernosum  penis.  2'.  Corpus 
spongiosum.  3.  Prostate  glnnd,  with  a  portion  of  the  levator  ani  covering  its 
fore  part.  4.  Urinary  bladder.  5.  Intestinum  rectum.  6.  Deep  perineal 
fascia — its  two  layers.  7.  Cut  edge  of  the  pelvic  fascia,  extending  from  the 
pubes  to  the  back  part  of  the  prostate.  8.  Vas  deferens.  8'.  Vesiculn  seminalis. 
9.  Ureter.  The  cut  edge  of  the  peritoneum  is  seen  jagged  over  the  bladder  and 
the  rectum. 

39 


458  THE   DISSECTOR. 

It  proceeds  from  the  summit  of  the  bladder,  and  ascends  along 
the  linea  alba  to  the  umbilicus. 

The  posterior  false  ligaments  are  the  fold  of  peritoneum  formed 
on  each  side  of  the  pelvis  by  the  obliterated  hypogastric  artery ; 
this  fold  also  contains  the  ureter  and  the  vessels  and  nerves  of 
the  bladder. 

The  lateral  false  ligaments  are  formed  by  the  passage  of  the 
peritoneum,  from  the  side  of  the  pelvis  to  the  side  of  the  bladder. 
The  obliterated  hypogastric  artery  lies  along  the  line  of  reflection 
of  the  membrane. 

The  superior  or  suspensory  false  ligament  is  the  fold  of  peri- 
toneum caused  by  the  prominence  of  the  cord  of  the  urachus  and 
the  cords  of  the  obliterated  hypogastric  arteries. 

The  bladder  is  composed  of  four  coats — serous,  muscular,  cel- 
lular, and  mucous. 

The  serous  coat  is  partial  and  derived  from  the  peritoneum,  which 
invests  the  posterior  surface  and  sides  of  the  bladder  from  about  oppo- 
site the  point  of  termination  of  the  ureters  to  its  summit,  whence  it  is 
guided  to  the  anterior  wall  of  the  abdomen  by  the  hypogastric  cords  and 
urachus. 

The  muscular  coat  consists  of  two  layers :  an  external  layer  composed 
of  longitudinal  fibres,  the  detrusor  urinae  ;  and  an  internal  layer  of  ob- 
lique and  circular  fibres  irregularly  distributed.  The  longitudinal  fibres 
arise  from  the  anterior  ligaments  of  the  bladder  (tendons  of  the  detrusor 
urinse),  the  neck  of  that  organ,  and  the  base  of  the  prostate  gland,  and 
spread  out  as  they  ascend  to  the  fundus ;  here  a  small  fasciculus  follows 
the  course  of  the  urachus,  but  the  greater  number  converge  upon  the 
posterior  surface  of  the  organ  and  descend  to  its  neck,  where  they  are 
inserted  into  the  isthmus  of  the  prostate  gland,  and  into  a  ring  of  mus- 
cular tissue,  which  surrounds  the  commencement  of  the  prostatic  portion 
of  the  urethra.  In  the  female  they  are  inserted  into  the  vagina.  The 
lateral  fibres  commence  at  the  prostate  gland  and  muscular  ring  of  the 
urethra  on  one  side,  and  spread  out  as  they  ascend  upon  the  side  of  the 
bladder,  to  descend  upon  the  opposite  side,  and  be  inserted  into  the  pros- 
tate and  opposite  segment  of  the  same  ring.  Two  bands  of  oblique 
fibres  are  described  by  Sir  Charles  Bell,  as  originating  at  the  termina- 
tions of  the  ureters,  and  converging  to  the  neck  of  the  bladder ;  the  ex- 
istence of  these  muscles  is  not  well  established.  The  fibres  corresponding 
with  the  trigonum  vesicae  are  transverse. 

Mr.  Guthrie1  observes  that  there  are  no  fibres  at  the  neck  of  the  blad- 
der capable  of  forming  a  sphincter  vesicae ;  but  Mr.  Lane2  has  described 
a  fasciculus  of  muscular  fibres  which  surround  the  commencement  of  the 
urethra,  and  perform  such  an  office.  These  fibres  form  a  narrow  bundle 
above  the  urethra,  but  spread  out  below,  behind  the  prostate  gland :  they 
are  brought  into  view  by  dissecting  off  the  mucous  membrane  from 
around  the  orifice  of  the  urethra. 

Sir  Astley  Cooper  has  described  around  the  urethra,  within  the  pros- 


1  "  On  the  Anatomy  and  Diseases  of  the  Neck  of  the  Bladder  and  of 
the  Urethra." 
*  Lancet,  vol.  i.,  1842-3,  p.  670. 


URINARY  BLADDER.  459 

tate  gland,  a  ring  of  elastic  tissue,  or,  rather,  according  to  Mr.  Lane,  of 
muscular  fibres,  which  has  for  its  object  the  closure  of  the  urethra  against 
the  involuntary  passage  of  the  urine.  It  is  into  this  ring  that  the  longi- 
tudinal fibres  of  the  detrusor  urinae  are  inserted,  so  that  the  muscle, 
taking  a  fixed  point  at  the  pubes,  will  not  only  compress  the  bladder, 
and  thereby  tend  to  force  its  contents  along  the  urethra,  but  will  at 
the  same  time,  by  means  of  its  attachment  to  the  ring,  dilate  the  en- 
trance of  the  urethra,  and  afford  a  free  egress  to  the  contents  of  the 
bladder. 

The  cellular,  or  submucous  coat,  is  the  thick  layer  of  cellular  tissue, 
which  is  interposed  between  the  mucous  and  muscular  coat,  and  forms 
the  bond  of  union  between  them. 

The  mucous  coat  is  thin  and  smooth,  of  a  pale  rose  color,  and  exactly 
moulded  on  the  muscular  coat,  to  which  it  is  connected  by  the  cellular 
coat ;  its  papillae  are  very  minute,  and  there  are  a  number  of  mucous 
follicles,  especially  near  the  neck  of  the  organ.  This  mucous  membrane 
is  continuous,  through  the  ureters,  with  the  lining  membrane  of  the  uri- 
niferous  ducts,  and  through  the  urethra,  with  that  of  the  prostatic  ducts, 
tubuli  seminiferi,  and  Cowper's  glands.  The  cells  of  the  epithelium  are 
of  the  spheroidal  kind. 

Upon  the  internal  surface  of  the  base  of  the  bladder  is  a  tri- 
angular smooth  plane,  of  a  paler  color  than  the  rest  of  the 
mucous  membrane,  the  trigonnm  vesic®,  or  trigone  vesicate. 
This  is  the  most  sensitive  part  of  the  bladder,  and  the  pressure 
of  calculi  upon  it  gives  rise  to  great  suffering.  It  is  bounded  on 
each  side  by  the  raised  ridge,  corresponding  with  the  muscles  of 
the  ureters,  at  each  posterior  angle  by  the  openings  of  the  ureters, 
and  in  front  by  a  slight  elevation  of  the  mucous  membrane  at  the 
entrance  of  the  urethra,  called  uvula  vesicce. 

The  external  surface  of  the  base  of  the  bladder  corresponding 
with  the  trigonura,  is  also  triangular,  and  is  separated  from  the 
rectum  by  a  thin  layer  of  fibrous  membrane,  derived  from  the 
recto-vesical  fascia.  It  is  bounded  behind  by  the  recto-vesical 
fold  of  peritoneum;  and  on  each  side  by  the  vas  deferens  and 
vesicula  seminalis,  which  converge  almost  to  a  point  at  the  base 
of  the  prostate  gland.  It  is  through  this  space  that  the  open- 
ing is  made  in  the  recto-vesical  operation  for  puncture  of  the 
bladder. 

The  arteries  of  the  urinary  bladder  are  the  superior  vesical,  three  or 
four  small  branches  which  proceed  from  the  commencement  of  the  hypo- 
gastric  artery,  previously  to  its  complete  obliteration  ;  and  the  inferior 
vesical,  from  the  internal  iliac.  The  latter  is  distributed  to  the  base  of 
the  bladder,  vesiculae  seminales,  and  prostate  gland.  The  veins  are 
numerous  and  of  large  size,  and  form  a  plexus  around  the  neck  and  at 
the  base  of  the  bladder;  the  plexus  communicates  with  the  prostatic 
plexus  and  with  the  hemorrhoidal  veins.  The  nerves  of  the  bladder  are 
derived  from  the  inferior  hypogastric  plexuses  and  their  communications 
with  the  third  and  fourth  sacral  nerves. 


460  THE   DISSECTOR. 


PROSTATE  GLAND. 

The  prostate  gland  (rtpoietwt,  pneponere)  is  situated  in  front 
of  the  neck  of  the  bladder,  behind  the  triangular  ligament  and 
pelvic  fascia,  and  upon  the  rectum,  through  which  latter  it  may 
be  felt  with  the  finger.  It  surrounds  the  commencement  of  the 
urethra  for  somewhat  more  than  an  inch  of  its  extent,  and 
resembles  a  Spanish  chestnut  both  in  size  and  form ;  the  base 
being  directed  backwards  towards  the  neck  of  the  bladder,  the 
apex  forwards,  and  the  convex  side  towards  the  rectum.  It  is 
retained  firmly  in  position  by  the  anterior  and  lateral  ligaments 
of  the  bladder,  and  by  a  process  of  the  recto-vesical  fascia,  which 
forms  a  sheath  around  it.  It  consists  of  three  lobes,  two  lateral 
and  a  middle  lobe  or  isthmus ;  the  lateral  lobes  are  distinguished 
by  an  indentation  on  the  base  of  the  gland,  and  a  slight  furrow 
on  its  upper  and  lower  surface.  The  third  lobe,  or  isthmus,  is  a 
small  transverse  band  which  passes  between  the  two  lateral  lobes 
at  the  base  of  the  organ. 

In  structure,  the  prostate  gland  is  composed  of  ramified  ducts,  termi- 
nating in  lobules  of  follicular  pouches,  which  are  so  closely  compressed 
as  to  give  to  a  thin  section  of  the  gland  a  cellular  appearance.  It  is 
pale  in  color  and  hard  in  texture,  splits  easily  in  the  course  of  its  ducts, 
and  is  surrounded  by  a  proper  fibrous  covering,  and  by  a  plexus  of  veins 
which  are  inclosed  by  the  sheath  derived  from  the  recto-vesical  fascia. 
Its  secretion  is  poured  into  the  prostatic  portion  of  the  urethra  by  fifteen 
or  twenty  excretory  ducts.  The  ducts  of  the  lateral  lobes  open  into  the 
urethra  on  each  side  of  the  veru  montanum ;  those  of  the  third  lobe  open 
upon  and  behind  the  veru.  The  urethra,  in  passing  through  the  prostate, 
lies  one-third  nearer  its  upper,  than  its  lower  surface. 

The  arteries  of  the  prostate  gland  are  small,  and  derived  from  the  infe- 
rior vesical  and  middle  hemorrhoidal.  The  veins  form  a  plexus  around 
the  gland,  which  receives  from  the  front  the  veins  of  the  penis,  and  termi- 
nates in  the  vesical  plexus. 

VESICTIL^E    SEMINALES. 

On  the  under  surface  of  the  base  of  the  bladder,  and  converging 
towards  the  base  of  the  prostate  gland,  are  two  tabulated  and 
somewhat  pyriform  bodies,  about  two  inches  in  length,  the  vesi- 
culse  seminales.  Their  upper  surface  is  in  contact  with  the  base 
of  the  bladder ;  the  under  side  rests  on  the  rectum,  separated 
only  by  a  process  derived  from  the  recto-vesical  fascia  ;  the  larger 
extremities  are  directed  backwards  and  outwards,  and  the  smaller 
ends  almost  meet  at  the  base  of  the  prostate.  They  inclose 
between  them  a  triangular  space,  which  is  bounded  posteriorly  by 
the  recto-vesical  fold  of  peritoneum,  and  corresponds  with  the 
trigonum  vesicae  on  the  interior  of  the  bladder.  Each  vesicula  is 
formed  by  the  convolutions  of  a  single  tube,  which  gives  off  seve- 
ral irregular  csecal  branches.  It  is  inclosed  in  a  fibrous  mem- 


INTERNAL  ILIAC   ARTERY.  461 

brane,  derived  from  the  recto-vesical  fascia,  and  is  constricted 
beneath  the  isthmus  of  the  prostate  gland  into  a  small  excretory 
duct.  The  vas  deferens,  somewhat  enlarged  and  sacculated,  lies 
along  the  inner  border  of  each  vesicula,  and  is  included  in  its 
fibrous  investment.  It  communicates  with  the  duct  of  the  vesi- 
cula, beneath  the  isthmus  of  the  prostate,  and  forms  the  ejacula- 
tory  duct. 

The  ejaculatory  duct  is  about  three-quarters  of  an  inch  in 
length,  and  running  forwards,  first  between  the  base  of  the  pros- 
tate and  the  isthmus,  and  then  through  the  tissue  of  the  veru 
montanum,  opens  on  the  mucous  membrane  of  the  urethra,  by  the 
side  of,  or  within  the  aperture  of  the  sinus  pocularis. 

In  structure,  the  vesiculae  seminales  are  composed  of  three  coats  :  exter- 
nal, which  is  cellular ;  middle,  fibrous  and  contractile ;  and  internal  or 
mucous,  a  thin  mucous  membrane,  presenting  a  delicate  reticular  mark- 
ing, like  that  of  the  gall-bladder,  and  invested  by  a  squamous  epithe- 
lium. 

The  bladder  and  rectum  may  now  be  turned  down,  and  the  peritoneum 
removed  from  the  right  wall  of  the  pelvis.  This  will  bring  into  view  the 
pelvic  fascia  and  its  recto-vesical  layer,  which  may  be  examined  from  the 
inside.  In  the  next  place  the  internal  iliac  artery  should  be  sought  for 
in  the  posterior  false  ligament  of  the  bladder,  and  the  cellular  tissue  and 
fat  which  conceal  it  and  its  branches  removed. 

The  ARTERIES  of  the  pelvis  are  the  internal  iliac  and  its  branches ; 
the  superior  hemorrhoidal,  from  the  inferior  mesenteric  ;  and  the 
arteria  sacra  media,  from  the  aorta. 

The  INTERNAL  ILIAC  ARTERY  is  a  short  trunk  between  one  and 
two  inches  in  length.  It  proceeds  from  the  common  iliac  artery, 
opposite  the  sacro-iliac  symphysis,  and  passes  obliquely  down- 
wards and  forwards,  to  a  level  with  the  upper  border  of  the 
sacro-ischiatic  foramen,  where  it  separates  into  an  anterior  and 
posterior  division.  From  the  extremity  of  the  artery,  a  fibrous 
cord  is  continued  onwards  by  the  side  of  the  bladder  to  near  its 
summit,  and  thence  onwards  by  the  side  of  the  linea  alba  to  the 
umbilicus :  this  is  the  remains  of  the  hypogastric  artery  of  the 
foetus. 

In  the  foetus  the  internal  iliac  artery,  under  the  name  of  hypo- 
gastric,  takes  the  course  just  indicated,  and  becomes  the  umbilical 
artery.  After  birth,  the  artery  ceases  to  be  pervious  beyond  the 
side  of  the  bladder,  where  it  gives  off  the  superior  vesical  arteries. 

The  internal  iliac  artery  is  in  relation  in  front  with  the  ureter ; 
behind,  with  the  internal  iliac  vein  ;  and  towards  the  wall  of  the 
pelvis,  with  the  sacral  plexus  and  pyriformis. 

The  branches  of  the  internal  iliac  are,  from  the  apterior  trunk, 
the— 


462 


THE   DISSECTOR. 


Superior  vesical,  Yaginal, 

Inferior  vesical,  Obturator, 

Middle  hemorrhoidal,  Ischiatic, 

Uterine,  Internal  pudic ; 

from  the  posterior  trunk,  the — 

Ilio-lumbar,  Lateral  sacral, 

Gluteal. 

The  superior  vesical  arteries  are  three  or  four  small  branches, 
which  proceed  from  the  pervious  portion  of  the  hypogastric  cord. 
They  are  distributed  to  the  upper  and  middle  part  of  the  bladder. 
From  one  of  these  there  passes  off  a  small  artery,  the  deferential, 
which  accompanies  the  vas  deferens  along  the  spermatic  cord. 

The  inferior  vesical,  somewhat  larger  than  the  preceding,  passes 
down  upon  the  side  of  the  bladder  to  its  base,  and  is  distributed 
to  that  region,  the  vesiculse  seminales,  and  prostate  gland. 


Fig.  141, 


LONGITUDINAL  SECTION  OF  THE 
PELVIS,  SHOWING  ITS  CAVITY  AND 
THE  INTERNAL  ILIAC  ARTERY. — 
a.  The  iliacus  interims  muscle, 
crossed  by  the  external  cutaneous 
nerve,  b.  The  psoas  muscle,  and 
genito-crural  nerve,  c.  The  in- 
ferior vena  cava.  d.  The  aorta. 
e.  The  right  common  iliac  artery. 
/.  The  left  common  iliac  artery 
and  vein.  g.  The  external  iliac 
artery  and  vein.  h.  The  circum- 
flexa  ilii  artery  inosculating  with 
i,  the  ilio-lumbar  artery,  k.  The 
epigastric  artery.  I.  The  obtura- 
tor internus  muscle,  in.  The  le- 
vator  ani.  n.  Part  of  the  prostate 
gland  supported  by  the  levatorani. 
o.  The  membranous  part  of  the 
urethra,  p.  The  bulb.  q.  The 
corpus  cavernosum  penis,  r,  r. 
The  sphincter  ani.  s.  The  lower 
extremity  of  the  rectum,  t.  The 
coccygeus  muscle.  v,  v.  The 
pyriformis  muscle,  crossed  by  the 
sacral  nerves.  w.  The  arteria 
sacra  media,  x.  The  internal  iliac 
artery,  y.  Its  anterior  trunk  ;  the 
artery  above  the  letter  is  the  un- 
obliterated  portion  of  the  hypo- 
gastric  artery,  which  gives  off  the 
superior  vesical  arteries,  and  be* 
comes  converted  into  a  fibrous  cord,  z.  The  artery  below  y,  is  the  obturator, 
and  the  nerve  above  it  the  obturator  nerve.  A  little  further  on  the  nerve  and 
artery  are  seen  passing  through  the  obturator  foramen.  1.  The  inferior  vesical 
artery,  giving  off  the  middle  hemorrhoidal.  2.  The  anterior  trunk,  dividing 
into  internal  pudic  and  ischiatic.  3.  The  ilio-lumbar  artery.  4.  The  lateral 
sacral  artery,  sending  branches  into  the  anterior  sacral  foramina.  5.  The  glu- 
teal  artery.  6,  6.  The  sacrum.  7.  The  coccyx.  8.  The  symphysis  pubis.  9, 
The  suspensory  ligament  of  the  penia. 


INTERNAL   PUDIC   ARTERY.  463 

The  middle  hemorrhoidal  artery,  frequently  a  branch  of  the 
preceding,  passes  downwards  to  the  rectum,  to  which  it  is  distri- 
buted, inosculating  with  the  superior  and  inferior  hemorrhoidal 
arteries.  In  the  female,  it  distributes  branches  to  the  vagina. 

The  uterine  artery  passes  downwards  between  the  layers  of  the 
broad  ligament,  to  the  neck  of  the  uterus,  and  then  ascends  in  a 
tortuous  course  along  its  lateral  border,  between  the  layers  of  the 
broad  ligament.  It  gives  off  branches  to  the  vagina,  the  lower 
part  of  the  bladder,  the  Fallopian  tube,  and  round  ligament,  and 
inosculates  with  the  spermatic  or  ovarian  artery. 

The  vaginal  artery  corresponds  in  position  with  the  inferior 
vesical,  and  is  distributed  to  the  vagina  and  neighboring  parts  of 
the  bladder  and  rectum. 

The  OBTURATOR  ARTERY,  sometimes  a  branch  of  the  posterior 
division,  passes  forwards  below  the  brim  of  the  pelvis  to  the  upper 
part  of  the  obturator  foramen,  through  which  it  escapes  into  the 
thigh. 

Its  branches  within  the  pelvis  are  :  an  iliac  branch,  which  sup- 
plies the  bone  of  the  iliac  fossa,  and  inosculates  with  the  ilio- 
lumbar  artery ;  and  a  pubic  branch  which  is  given  off  close  to  the 
obturator  foramen,  and  inosculates  with  its  fellow  of  the  opposite 
side,  behind  the  pubes,  and  with  the  pubic  branch  of  the  epigas- 
tric artery. 

The  ISCHIATIC  ARTERY  is  the  larger  of  the  two  terminal  branches 
of  the  anterior  division  of  the  internal  iliac.  It  passes  down- 
wards in  front  of  the  pyriformis  and  sacral  plexus  of  nerves,  and 
internally  to  the  pudic  artery,  to  the  lower  part  of  the  great 
ischiatic  foramen,  where  it  escapes  from  the  pelvis  between  the 
lower  border  of  the  pyriformis  and  the  coccygeus,  to  both  of  which 
it  distributes  branches. 

The  INTERNAL  PUDIC  ARTERY,  the  other  terminal  branch  of  the 
anterior  division  of  the  internal  iliac,  descends  externally  to  the 
ischiatic  artery  to  the  lower  part  of  the  great  ischiatic  foramen, 
and  passes  through  the  foramen  between  the  lower  border  of  the 
pyriformis  and  coccygeus.  It  then  crosses  the  spine  of  the 
ischium,  and  re-enters  the  pelvis  through  the  lesser  ischiatic 
foramen.  In  the  next  place  it  passes  forward  upon  the  obturator 
fascia,  and  above  the  tuberosity  of  the  ischium,  to  the  perineum, 
to  which  it  is  distributed. 

The  branches  of  the  internal  pndic  artery  within  the  pelvis  are 
several  small  twigs  to  the  levator  ani  and  sacral  nerves,  and  occa- 
sionally a  branch  which  takes  the  place  of  the  inferior  vesical  or 
middle  hemorrhoidal  artery. 

POSTERIOR  DIVISION. — The  ILIO-LUMBAR  ARTERY  ascends  be- 
neath the  external  iliac  vessels  and  psoas  muscle,  to  the  posterior 
part  of  the  crest  of  the  ilium,  where  it  divides  into  two  branches: 


464 


THE   DISSECTOR. 


a  lumbar  branch,  which  supplies  the  psoas  and  quadratns  lumbo- 
rum  muscles,  and  sends  a  ramuscule  through  the  fifth  interverte- 


142. 


THE  DISTRIBUTION  AND  BRANCHES  OF  THE  ILIAC  ARTERIES. — 1.  The  aorta. 
2.  The  left  common  iliac  artery.  3.  The  external  iliac.  4.  The  epigastric 
artery.  5.  The  circumflexa  ilii.  6.  The  internal  iliac  artery.  7.  Its  anterior 
trunk.  8.  Its  posterior  trunk.  9.  The  umbilical  artery  giving  off  (10)  the 
superior  vesical  artery.  After  the  origin  of  this  branch,  the  umbilical  artery 
becomes  converted  into  a  fibrous  cord — the  umbilical  ligament.  11.  The  inter- 
nal pudic  artery  passing  behind  the  spine  of  the  ischium  (12)  and  lesser  sacro- 
ischiatic  ligament.  13.  The  middle  hemorrhoidal  artery.  14.  The  ischiatic 
artery,  also  passing  behind  the  anterior  sacro-ischiatic  ligament  to  escape  from 
the  pelvis.  15.  Its  inferior  vesical  branch.  16.  The  ilio-lumbar,  the  first 
branch  of  the  posterior  trunk  (8)  ascending  to  inosculate  with  the  circumflexa 
ilii  artery  (5)  and  form  an  arch  along  the  crest  of  the  ilium.  17.  The  obturator 
artery.  18.  The  lateral  sacral.  19.  The  gluteal  artery  escaping  from  the  pelvis 
through  the  upper  part  of  the  great  sacro-ischiatic  foramen.  20.  The  sacra- 
media.  21.  The  right  common  iliac  artery  cut  short.  22.  The  femoral  artery. 

bral  foramen  to  the  spinal  cord  and  its  membranes  ;  and  an  iliac 
branch,  which  passes  across  the  iliac  fossa  to  the  crest  of  the 
ilium,  where  it  inosculates  with  the  lumbar  and  circumflexa  ilii 
arteries.  In  its  course  it  distributes  branches  to  the  iliacus  and 
abdominal  muscles. 

The  LATERAL  SACRAL  ARTERIES  are  generally  two  in  number 
on  each  side,  superior  and  inferior.  The  superior  passes  inwards 
to  the  first  sacral  foramen,  and  is  distributed  to  the  contents  of 
the  spinal  canal,  from  which  it  escapes  by  the  posterior  sacral 
foramen,  and  supplies  the  integument  on  the  dorsum  of  the 
sacrum.  The  inferior  passes  down  by  the  side  of  the  anterior 
sacral  foramina  to  the  coccyx ;  it  first  pierces  and  then  rests  upon 
the  origin  of  the  pyriformis,  and  sends  branches  into  the  sacral 
canal,  to  supply  the  sacral  nerves.  Both  arteries  inosculate  with 
each  other  and  with  the  sacra  media. 


INTERNAL  ILIAC   VEIN.  465 

The  GLUTEAL  ARTERY  is  the  continuation  of  the  posterior  trunk 
of  the  internal  iliac :  it  passes  backwards  between  the  lumbo- 
sacral  and  first  sacral  nerve  through  the  upper  part  of  the  great 
sacro-ischiatic  foramen  and  above  the  pyriformis  muscle.  While 
within  the  pelvis  it  gives  off  some  muscular  twigs  to  the  iliacus 
and  pyriformis  muscle  ;  and  at  its  escape  from  the  pelvis,  a  nutri- 
tious artery  to  the  ilium. 

The  superior  hemorrhoidal  artery  is  the  continuation  of  the 
inferior  mesenteric  artery  into  the  pelvis ;  it  divides  in  the  meso- 
rectum  into  two  branches,  which  are  distributed  on  each  side  of 
the  rectum  as  far  as  its  lower  part,  and  inosculates  with  the 
middle  and  inferior  hemorrhoidal  arteries. 

The  arteria  sacra  media  descends  along  the  middle  of  the 
sacrum  from  the  bifurcation  of  the  aorta.  It  gives  off  lateral 
b ranches,  which  inosculate  with  the  lateral  sacral  arteries,  and 
terminates  on  the  coccyx. 

The  VEINS  of  the  pelvis  unite  to  form  the  internal  iliac  vein. 

The  INTERNAL  ILIAC  VEIN  receives  the  returning  blood  by  the 
gluteal,  ischiatic,  internal  pudic,  and  obturator  veins  from  the 
exterior  of  the  pelvis,  and  by  the  vesical  and  uterine  plexuses 
from  within.  It  lies  at  first  to  the  inner  side  and  then  behind 
the  internal  iliac  artery,  and  terminates  by  uniting  with  the  ex- 
ternal iliac  vein,  to  form  the  common  iliac  vein. 

The  vesical  and  prostatic  plexus  surrounds  the  neck  and  base 
of  the  bladder,  the  prostate  gland,  and  membranous  portion  of 
the  urethra.  It  receives  the  veins  from  the  external  organs  of 
generation,  the  dorsal  vein  of  the  penis,  after  piercing  the  trian- 
gular ligament,  dividing  into  two  branches  before  joining  it.  The 
plexus  is  surrounded  by  the  sheath  of  pelvic  fascia  which  incloses 
the  prostate  gland,  and  spreads  over  the  base  of  the  bladder. 

The  internal  pudic  vein,  besides  the  branches  which  accompany 
the  internal  pudic  artery,  receives  a  hemorrhoidal  vein  from  a 
plexus  which  surrounds  the  lower  part  of  the  rectum,  the  hemor- 
rlioiilal  plexus. 

The  uterine  and  vaginal  plexus  is  situated  around  the  vagina 
and  upon  the  sides  of  the  uterus ;  above,  it  is  in  communication 
with  the  ovarian  plexus. 

The  ilio-lumbar  and  lateral  sacral  veins  terminate  in  the  com- 
mon iliac  vein ;  and  the  middle  sacral  vein,  in  the  left  common 
iliac  vein. 

The  LYMPHATIC  VESSELS  of  the  pelvis  are  those  proceeding  from 
the  deeper  structures  of  the  external  organs  of  generation,  the 
walls  and  viscera  of  the  pelvis.  They  terminate  in  a  chain  of 
alands,  situated  in  the  course  of  the  iliac  vessels^  and  the  efferent 
ducts  of  the  latter  unite  with  the  lumbar  glands. 

The  NERVES  of  the  pelvis  are  the  five  sacral  and  coccygeal  nerve 


466  THE  DISSECTOR. 

derived  from  the  spinal  cord,  the  hypogastric  plexus,  and  the 
trunk  of  the  sympathetic. 

The  SACRAL  NERVES  are  five  in  number  on  each  side  ;  the  an- 
terior divisions  of  the  four  upper  nerves  issue  from  the  sacrum 
through  the  anterior  sacral  foramina,  the  fifth  escapes  between 
the  sacrum  and  coccyx,  and  pierces  the  coccygeus  muscle.  The 
two  upper  nerves  are  of  large  size  ;  the  third  is  scarcely  one-fourth 
as  large  as  the  second  ;  the  fourth  is  much  smaller  than  the  third ; 
and  the  fifth  than  the  fourth.  The  first  three  nerves,  with  a  part 
of  the  fourth  and  the  lumbo-sacral  nerve,  unite  to  form  the  sacral 
plexus. 

The  fourth  sacral  nerve  divides  into  two  branches,  one  of  which 
assists  in  forming  the  sacral  plexus,  the  other  separates  into  three 
branches  :  a  communicating  branch,  to  unite  with  the  fifth  sacral 
nerve ;  a  visceral  branch,  to  join  with  the  hypogastric  plexus  and 
supply  the  bladder  and  prostate  gland,  and  in  the  female,  the 
vagina ;  and  a  muscular  branch  which  sends  filaments  to  the  le- 
vator  ani  and  coccygeus  and  an  hemorrhoidal  branch  to  the 
sphincter  ani  and  integument  behind  the  anus. 

The  fifth  sacral  nerve,  issuing  from  between  the  sacrum  and 
coccyx,  pierces  the  coccygeus  muscle,  and  receives  the  communi- 
cating branch  from  the  fourth ;  it  then  communicates  with  the 
coccygeal  nerve,  and  piercing  the  coccygeus  a  second  time,  is 
distributed  to  the  integument  over  the  dorsal  surface  of  the  coccyx. 

The  coccygeal  nerve  pierces  the  coccygeus  muscle,  and  unites 
with  the  fifth  sacral  nerve,  in  which  it  is  lost. 

Each  of  the  anterior  divisions  of  the  sacral  nerves  receives  a 
filament  from  the  sympathetic  at  its  point  of  escape  from  the  sacral 
canal. 

SACRAL  PLEXUS. — The  sacral  plexus  is  formed  by  the  union 
of  the  lumbo-sacral,  the  three  upper  sacral  nerves,  and  one  half 
the  fourth.  It  is  triangular  in  form,  its  base  corresponding  with 
the  whole  length  of  the  sacrum,  and  its  apex  with  the  lower  part 
of  the  great  sacro-ischiatic  foramen.  It  rests  on  the  pyriformis 
muscle,  and  is  crossed  by  the  branches  of  the  internal  iliac  vessels. 

The  branches  of  the  sacral  plexus  are  chiefly  destined  for  the 
supply  of  the  lower  limb,  and  are  given  off  externally  to  the  pel- 
vis ;  those  which  proceed  from  the  plexus  within  the  pelvis,  are 
some  muscular  branches  to  the  pyriformis,  and  obturator  internus, 
the  superior  gluteal  nerve,  and  pudic. 

The  branches  to  the  pyriformis  muscle  are  commonly  two  in 
number ;  the  branch  to  the  obturator  internus  passes  out  of  the 
pelvis  through  the  great  sacro-ischiatic  foramen,  with  the  internal 
pudic  vessels  an$  nerve  crosses  the  spine  of  the  ischium,  and  re- 
enters  the  pelvis  through  the  lesser  sacro-ischiatic  foramen,  to  be 
distributed  to  the  muscle. 


HYPOGASTRIO  PLEXUS.  46f 

The  SUPERIOR  GLUTEAL  NERVE  arises  from  the  lumbo-sacral 
nerve,  near  its  junction  with  the  first  sacral  nerve,  and  passes  out 
of  the  pelvis  through  the  upper  part  of  the  great  sacro-rschiatic 
foramen,  above  the  pyriformis  muscle.  It  is  distributed  to  the 
gluteal  muscles. 

The  PUDIC  NERVE  arises  from  the  lower  part  of  the  sacral 
plexus,  and  passes  out  of  the  pelvis  through  the  great  sacro- 
ischiatic  foramen,  below  the  pyriformis  muscle.  It  crosses  the 
spine  of  the  ischium,  and  re-entering  the  pelvis  through  the  lesser 
sacro-ischiatic  foramen,  accompanies  the  internal  pudic  artery 
along  the  outer  wall  of  the  ischio-rectal  fossa  to  the  perineum. 
In  its  course  along  the  ischio-rectal  fossa,  it  lies  below  the  artery, 
and  divides  into  two  branches,  perineal  and  dorsal  artery  of  the 
penis. 

Near  its  origin  the  pudic  nerve  gives  off  the  inferior  hemor- 
rhoidal  nerve,  which  passes  through  the  lesser  sacro-ischiatic 
foramen,  and  crosses  the  ischio-rectal  fossa  with  one  of  the  infe- 
rior hemorrhoidal  arteries,  to  be  distributed  to  the  sphincter  ani- 
and  integument  around  the  anus.  This  nerve  sometimes  proceeds 
directly  from  the  sacral  plexus. 

SYMPATHETIC  NERVE. —  The  sympathetic  nerve  within  the 
pelvis  consists  of  the  trunk  of  the  nerve,  and  the  pre-vertebral 
portion. 

The  trunk  of  the  nerve  presents  four  or  five  small  fusiform 
ganglia,  situated  on  the  sacrum  close  to  the  anterior  sacral  fora- 
mina; the  uppermost  ganglion  communicates  with  the  last  of  the 
lumbar  ganglia;  the  lowest  ganglion  of  each  side  communicates 
with  a  small  ganglion  situated  on  the  first  bone  of  the  coccyx,  the 
ganglion  impar,  or  azygos,  which  thus  becomes  the  bond  of  union 
between  the  extremities  of  the  two  sympathetic  nerves. 

The  branches  of  the  sacral  ganglia  are — branches  of  communi- 
cation, and  branches  of  distribution. 

The  branches  of  communication  are  two  from  each  ganglion, 
which  pass  outwards,  to  communicate  with  the  anterior  sacral 
nerves,  and  with  the  coccygeal  nerve. 

The  branches  of  distribution  pass  inwards  upon  the  front  of 
the  sacrum,  and  follow  the  course  of  the  branches  of  the  arteria 
sacra  media.  Other  branches,  proceeding  from  the  first  and 
second  ganglia,  join  the  hypogastric  plexus  ;  and  a  third  set, 
issuing  from  the  ganglion  impar  and  its  communicating  cords,  is 
distributed  to  the  coccyx. 

HYPOGASTRIC  PLEXUS. — The  pre-vertebral  portion  of  the 
sympathetic  system,  within  the  pelvis,  consists  of  the  hypo- 
gastric  plexus  and  its  lateral  divisions,  the  inferior  hypogastric 
plexuses. 

The  hypogastric  plexus  is  the  prolongation  of  the  aortic  plexus 


468  THE  DISSECTOR. 

into  the  pelvis.  It  is  situated  over  the  front  of  the  sacrum  at  its 
upper  part,  and  divides  into  two  lateral  portions,  the  inferior 
hyp ogastric  plexuses,  which  descend  to  the  sides  of  the  base  of  the 
bladder,  vagina,  and  rectum. 

Each  inferior  hypogastric  plexus  receives  branches  from  the 
third  and  fourth  sacral  nerves,  and  gives  off  plexuses,  which  ac- 
company the  branches  of  the  internal  iliac  artery,  and  take  the 
names  of  the  respective  arteries.  The  inferior  hypogastric  plexus 
supplies  the  bladder,  prostate  gland,  vesiculse  seminales,  corpus 
cavernosum,  penis,  rectum;  and,  in  the  female,  the  vagina,  uterus 
with  its  appendages,  and  ovaries. 

MALE   ORGANS   OF   GENERATION. 

The  organs  of  generation  in  the  male  are — the  penis  and  testes, 
with  their  appendages. 

PENIS. 

The  penis  is  divisible  into  a  body,  root,  and  extremity. 

The  body  is  surrounded  by  a  thin  integument,  which  is  remark- 
able for  the  looseness  of  its  cellular  connection  with  the  deeper 
parts  of  the  organ,  and  for  containing  no  adipose  tissue.  The 
root  is  broad,  and  firmly  adherent  to  the  rami  of  the  pubes  and 
ischium  by  means  of  two  strong  processes,  the  crura,  and  is  con- 
nected to  the  symphysis  pubis  by  a  fibrous  membrane,  the  liga- 
mentum  suspensorium. 

The  extremity,  or  glans  penis,  resembles  an  obtuse  cone,  some- 
what compressed  from  above  downwards,  and  of  a  deeper  red 
color  than  the  surrounding  skin.  At  its  apex  is  a  small  vertical 
slit,  the  meatus  urinarius,  which  is  bounded  by  two,  more  or  less 
protuberant  labia ;  and,  extending  backwards  from  the  meatus, 
is  a  depressed  raphe,  to  which  is  attached  a  loose  fold  of  mucous 
membrane,  the  fraenum  praputii.  The  base  of  the  glans  is 
marked  by  a  projecting  collar,  the  corona  glandis,  upon  which 
are  seen  a  number  of  small  papillary  elevations,  the  glandulae 
Tysoni  (odoriferae). 

Behind  the  corona  is  a  deep  fossa  (fossa  glandis,  cervix), 
bounded  by  a  circular  fold  of  integument,  the  pfceputium,  which, 
in  the  quiescent  state  of  the  organ,  may  be  drawn  over  the  glans, 
but,  in  its  distended  state,  is  obliterated,  and  serves  to  facilitate 
its  enlargement.  The  internal  surface  of  the  prepuce  is  lined  by 
mucous  membrane,  covered  by  a  thin  epithelium  ;  this  membrane 
is  reflected  over  the  glans  penis,  and,  at  the  meatus  urinarius,  is 
continuous  with  the  mucous  lining  of  the  urethra. 

In  dissecting  the  penis,  an  incision  should  be  made  along  the  middle 
of  the  dorsuin  of  the  organ,  and  the  integument  turned  aside.  Then  the 


PENIS.  469 

superficial  fascia  may  be  dissected  back  and  the  ligamentum  suspenso- 
rium  and  dorsal  vessels  and  nerves  brought  into  view. 

The  superficial  fascia  is  thin,  and  its  cellular  structure  free 
from  fat ;  it  is  continuous  with  the  superficial  fascia  of  the  abdo- 
men above,  and  with  the  dartos  and  superficial  fascia  of  the  peri- 
neum below. 

The  ligamentum  suspensorium  penis  is  a  strong  fibrous  mem- 
brane of  triangular  form,  attached  by  its  apex  to  the  symphysis 
pubis  ;  and  by  its  base,  to  the  body  of  the  penis.  Near  its  attach- 
ment it  separates  into  two  layers,  between  which  the  dorsal  ves- 
sels and  nerves  take  their  course. 

The  penis  is  composed  of  the  corpus  cavernosum  and  corpus 
spongiosum,  and  contains  in  its  interior  the  longest  portion  of 
the  urethra. 

The  corpus  cavernosum  is  distinguished  into  two  lateral  por- 
tions (corpora  cavernosa)  by  an  imperfect  septum,  and  by  a  supe- 
rior and  inferior  groove,  and  is  divided  posteriorly  into  two 
crura.  It  is  firmly  adherent,  by  means  of  its  crura,  to  the  rami 
of  the  pubes  and  ischium  ;  and  each  crus,  previously  to  its  junction 
with  its  fellow,  presents  a  slight  enlargement,  which  has  been 
named  by  Kobelt  the  bulb.  The  corpus  cavernosum  forms,  ante- 
riorly, a  single  rounded  extremity,  which  is  received  into  a  fossa 
in  the  base  of  the  glans ;  the  superior  groove  lodges  the  dorsal 
vessels  of  the  organ,  and  the  inferior  receives  the  corpus  spon- 
giosum. Its  fibrous  tunic  is  thick,  elastic,  and  extremely  firm, 
and  sends  a  number  of  fibrous  bands  and  cords  (trabecula?)  in- 
wards from  its  inferior  groove,  which  cross  its  interior  in  a  radiat- 
ing direction,  and  are  inserted  into  the  inner  walls  of  the  tunic. 
These  trabeculas  are  most  abundant  on  the  middle  line,  where 
they  are  ranged  vertically,  side  by  side,  somewhat  like  the  teeth 
of  a  comb,  and  constitute  the  imperfect  partition  of  the  corpus 
cavernosum,  called  septum  pectiniforme.  The  septum  is  more 
complete  at  its  posterior  than  towards  its  anterior  part. 

The  tunic  of  the  corpus  cavernosum  consists  of  strong  longi- 
tudinal fibrous  fasciculi,  closely  interwoven  with  each  other.  Its 
internal  structure  is  composed  of  erectile  tissue. 

The  corpus  spongiosum  is  situated  along  the  under  surface  of 
the  corpus  cavernosum,  in  its  inferior  groove.  It  commences  by 
its  posterior  extremity  between  and  beneath  the  crura  penis, 
where  it  forms  a  considerable  enlargement,  the  bulb,  and  termi- 
nates anteriorly  by  another  expansion,  the  glans  penis.  Its  middle 
portion,  or  body,  is  nearly  cylindrical,  and  tapers  gradually  from 
its  posterior  towards  its  anterior  extremity.  The~bulb  is  adhe- 
rent to  the  iriangular  ligament  by  means  of  a  prolongation  of 
that  membrane ;  in  the  rest  of  its  extent  the  corpus  spongiosum 
40 


470  THE  DISSECTOR. 

is  attached  to  the  corpus  cavernosum  by  cellular  tissue,  and  by 
veins  which  wind  around  that  body  to  reach  the  dorsal  vein. 

It  is  composed  of  erectile  tissue,  inclosed  by  a  dense  fibrous 
layer,  much  thinner  than  that  of  the  corpus  cavernosum,  and 
contains  in  its  interior  the  spongy  portion  of  the  urethra,  which 
lies  nearer  its  upper  than  its  lower  wall.  The  bulb  exhibits  a 
tendency  to  division  into  two  lobes,  an  appearance  which  is  due 
to  the  existence  of  a  thin  longitudinal  septum  in  its  internal 
structure. 

Erectile  tissue  is  a  peculiar  cellulo-vascular  structure,  entering  in  con- 
siderable proportion  into  tlie  composition  of  the  organs  of  generation.  It 
consists  essentially  of  a  plexus  of  veins  so  closely  convoluted  and  inter- 
woven with  each  other,  as  to  give  rise  to  a  cellular  appearance  when 
examined  by  means  of  a  section.  The  veins  forming  this  plexus  are 
smaller  in  the  glans  penis,  corpus  spongiosum,  and  circumference  of  the 
corpus  cavernosum,  than  in  the  central  part  of  the  latter,  where  they  are 
large  and  dilated.  They  have  no  other  coat  than  the  internal  lining 
prolonged  from  the  neighboring  veins  ;  and  the  interstices  of  the  plexus 
are  occupied  by  a  peculiar  reddish  fibrous  tissue.  They  receive  their 
blood  from  the  capillaries  of  the  arteries  in  the  same  manner  as  veins  in 
general,  and  not  by  means  of  vessels  having  a  peculiar  form  and  distri- 
bution, as  described  by  Miiller.  The  helicine  arteries  of  that  physiolo- 
gist have  no  existence. 

Vessels  and  Nerves. — The  arteries  of  the  penis  are  derived  from  the 
internal  pudic ;  they  are,  the  arteries  of  the  bulb,  arteries  of  the  corpus 
cavernosum,  and  dorsales  penis.  Its  veins  are  superficial  and  deep.  The 
deep  veins  run  by  the  side  of  the  deep  arteries,  and  terminate  in  the 
internal  pudic  veins.  The  superficial  veins  escape  in  considerable  num- 
ber from  the  base  of  the  glans,  and  converge  on  the  dorsum  penis,  to 
form  a  large  dorsal  vein,  which  receives  other  veins  from  the  corpus 
cavernosum  and  spongiosum  in  its  course,  and  passes  backwards  between 
two  layers  of  the  ligamentum  suspensorium,  and  through  the  triangular 
ligament,  beneath  the  arch  of  the  pubes,  to  terminate  in  the  prostatic 
plexus.  Previously  to  its  termination  it  divides  into  two  trunks. 

The  lymphatics  terminate  in  the  inguinal  glands.  The  nerves  are 
derived  from  the  pudic  nerve,  sacral  plexus,  and  hypogastric  plexus. 

URETHRA. 

The  urethra  is  the  membranous  canal,  extending  from  the  neck 
of  the  bladder  to  the  meatus  urinarius.  It  is  curved  in  its  course, 
and  composed  of  two  layers,  a  mucous  coat  and  an  elastic  fibrous 
coat.  The  mucous  coat  is  thin  and  smooth;  it  is  continuous, 
internally,  with  the  mucous  membrane  of  the  bladder;  externally, 
with  the  investing  membrane  of  the  glans ;  and  at  certain  points 
of  its  extent,  with  the  lining  membrane  of  the  numerous  ducts 
which  open  into  the  urethra,  namely,  those  of  Cowper's  glands, 
the  prostate  gland,  vasa  deferentia,  and  vesiculae  seminales.  The 
elastic  fibrous  coat  varies  in  thickness  in  different  parts  of  the 
course  of  the  urethra :  it  is  thick  in  the  prostate  gland,  forms  a 
firm  investment  for  the  membranous  portion  of  the  canal,  and  is 


URETHRA.  4T1 

thin  in  the  spongy  portion,  where  it  serves  as  a  bond  of  connec- 
tion between  the  mucons  membrane  and  the  corpus  spongiosum. 
The  urethra  is  about  eight  inches  in  length,  and  is  divided  into  a 
prostatic,  membranous,  and  spongy  portion. 

The  prostatic  portion,  a  little  more  than  an  inch  in  length,  is 
situated  in  the  prostate  gland,  about  one-third  nearer  its  upper 
than  its  lower  surface,  and  extending  from  its  base  to  its  apex. 
Upon  its  lower  circumference  or  floor  is  a  longitudinal  ridge  or 
crest,  the  veru  montanum,  or  caput  gallinaginis;  and  on  each  side 
of  the  veru,  a  depressed  fossa,  the  prostatic  sinus,  in  which  are 
seen  the  numerous  openings  (fifteen  to  twenty)  of  the  prostatic 
ducts.  The  veru  montanum  is  most  prominent  in  the  centre  ;  and 
immediately  in  front  of  the  prominent  part,  is  the  opening  of  a 
small  caecal  sac,  the  sinus  pocularis,  or  utriculus  prostaticus.  This 
sac  is  the  analogue  of  the  uterus;  it  is  nearly  half  an  inch  in 
length,  and  extends  back  beneath  the  third  lobe  of  the  prostate. 
It  causes,  by  its  approach  to  the  surface,  the  prominence  of  the 
veru  raontanum,  and  is  composed  of  two  coats,  mucous  and 
fibrous.  The  fibrous  coat  is  thick,  and  contains  on  each  side  the 
ejaculatory  duct.  The  mucous  coat  is  provided  with  an  abund- 
ance of  muciparous  glands.  The  ejaculatory  ducts  terminate  on 
each  side  within  the  aperture  of  the  sinus  pocularis,  by  slit-like 
openings. 

When  the  sinus  pocularis  is  of  large  size,  it  is  capable  of  receiving  the 
point  of  a  small  catheter,  and  by  that  means  interfering  with  an  import- 
ant operation.  In  case  of  such  interruption,  the  point  of  the  instrument 
must  be  carried  along  the  upper  wall  of  the  urethra. 

The  prostatic  portion  of  the  urethra,  when  distended,  is  the 
most  dilated  part  of  the  canal ;  but,  excepting  during  the  pas- 
sage of  urine,  is  completely  closed,  by  means  of  a  ring  of  muscu- 
lar tissue,  which  encircles  the  urethra  as  far  as  the  anterior  extre- 
mity of  the  veru  montanum.  In  the  contracted  state  of  the 
urethra,  the  veru  montanum  acts  as  a  valve,  being  pressed  upwards 
against  the  roof  of  the  canal ;  but  during  the  action  of  the 
detrusor  muscle  of  the  bladder,  the  whole  ring  is  expanded  by  the 
longitudinal  muscular  fibres  which  are  inserted  into  it ;  and  the 
veru  is  especially  drawn  downwards  by  two  delicate  tendons, 
which  were  traced  by  Mr.  Tyrrell  from  the  posterior  fibres  of  the 
detrusor  into  the  tissue  of  this  process. 

The  membranous  portion,  the  narrowest  part  of  the  canal, 
measures  about  three  lines  in  diameter,  and  is  somewhat  less 
than  an  iqch  in  length.  It  extends  from  the  apex  of  the  prostate 
gland  to  the  bulb  of  the  corpus  spongiosum,  and  passes  through 
the  triangular  ligament.  Its  coats  are  the  mucous  membrane, 
elastic  fibrous  tissue,  and  compressor  urethra?  muscle.  The  sub- 
mucous  tissue  is  richly  supplied  with  vessels. 


472  THE   DISSECTOR. 

The  spongy  portion,  about  six  inches  in  length,  forms  the  rest 
of  the  extent  of  the  canal,  and  is  lodged  in  the  corpus  spongi- 
osum  from  its  commencement  at  the  triangular  ligament  to  the 
meatus  urinarius.  It  is  narrowest  in  the  body,  and  becomes 
dilated  at  each  extremity,  posteriorly  in  the  bulb,  where  it  is 
named  the  bulbous  portion,  and  anteriorly  in  the  glans  penis, 
where  it  forms  the  fossa  navicularis.  The  meatus  urinarius  is  the 
most  constricted  part  of  the  canal;  so  that  a  catheter,  which  will 
enter  that  opening,  may  be  passed  freely  through  the  whole  extent 
of  a  normal  urethra. 

Opening  into  the  bulbous  portion  are  two  small  excretory 
ducts  about  an  inch  in  length,  which  may  be  traced  backwards, 
between  the  coats  of  the  urethra  and  the  bulb,  to  the  under  part 
of  the  membranous  portion  behind  the  triangular  ligament,  where 
they  originate  in  two  small  lobulated  and  somewhat  compressed 
glands  of  about  the  size  of  peas.  These  are  Cowper's  glands : 
they  are  situated  immediately  beneath  the  membranous  portion 
of  the  urethra,  and  are  inclosed  by  the  lower  segment  of  the 
compressor  urethras  muscle,  so  as  to  be  subject  to  muscular  com- 
pression. Upon  the  whole  of  the  internal  surface  of  the  spongy 
portion  of  the  urethra,  and  especially  along  its  lower  surface, 
are  numerous  small  openings  or  lacunce,  which  are  the  apertures 
of  mucous  glands  situated  in  the  submucous  cellular  tissue. 
The  openings  of  these  lacuna?  are  directed  forwards,  and  are 
liable  occasionally  to  intercept  the  point  of  a  small  catheter  in 
its  passage  into  the  bladder.  At  about  an  inch  and  a  half  from 
the  opening  of  the  meatus,  in  the  upper  wall  of  the  urethra,  one 
of  these  lacuna?  is  generally  found  much  larger  than  the  rest,  and 
is  named  the  lacuna  magna.  In  a  preparation  of  this  lacuna, 
made  by  Sir  Astley  Cooper,  the  extremity  of  the  canal  presents 
several  large  primary  ramifications. 

TESTES. 

The  testes  are  two  small  glandular  organs,  suspended  from  the 
abdomen  by  the  spermatic  cords,  and  inclosed  in  an  external 
tegumentary  covering,  the  scrotum. 

The  SCROTUM  is  distinguished  into  two  lateral  halves  or  hemi- 
spheres by  a  raphe,  which  is  continued  anteriorly  along  the  under 
surface  of  the  penis,  and  posteriorly  along  the  middle  line  of  the 
perineum  to  the  anus.  Of  these  two  lateral  portions  the  left  is 
somewhat  longer  than  the  right,  and  corresponds  with  the  greater 
length  of  the  spermatic  cord  on  the  left  side. 

The  scrotum  is  composed  of  two  layers,  the  integument  and  a 
proper  covering,  the  dartos;  the  integument  is  extremely  thin, 
transparent,  and  abundant,  and  beset  by  a  number  of  hairs,  which 


TESTE8.  473 

issne  obliquely  from  the  skin,  and  have  prominent  roots.  The 
dartos  is  a  thin  layer  of  contractile  fibrous  tissue,  intermediate 
in  properties  between  muscular  fibre  and  elastic  tissue ;  it  forms 
the  proper  tunic  of  the  scrotum,  and  sends  inwards  a  septum 
(septum  scroti),  which  divides  it  into  two  cavities  for  the  two 
testes.  The  dartos  is  continuous  around  the  base  of  the  scrotum 
with  the  common  superficial  fascia  of  the  abdomen  and  perineum. 

The  SPERMATIC  CORD  is  the  medium  of  communication  between 
the  testes  and  the  interior  of  the  abdomen :  it  is  composed  of 
arteries,  veins,  lymphatics,  nerves,  the  excretory  duct  of  the  tes- 
ticle, and  investing  tunics.  It  commences  at  the  internal  abdomi- 
nal ring,  where  the  vessels  of  which  it  is  composed  converge,  and 
passes  obliquely  along  the  spermatic  canal ;  the  cord  then  escapes 
at  the  external  abdominal  ring,  and  descends  through  the  scrotum 
to  the  posterior  border  of  the  testicle.  The  left  cord  is  somewhat 
longer  than  the  right,  and  permits  the  left  testicle  to  reach  a 
lower  level  than  its  fellow. 

The  TESTIS  (testicle)  is  a  small,  oblong,  and  rounded  gland, 
about  an  inch  and  a  half  in  length,  somewhat  compressed  on  the 
sides  and  behind,  and  suspended  in  the  cavity  of  the  scrotum  by 
the  spermatic  cord. 

Its  position  in  the  scrotum  is  oblique;  so  that  the  upper  ex- 
tremity is  directed  upwards  and  forwards,  and  a  little  outwards; 
the  lower,  downwards  and  backwards,  and  a  little  inwards;  the 
convex  border  looks  forwards  and  downwards;  and  the  flattened 
border,  to  which  the  cord  is  attached,  backwards  and  upwards. 
Lying  against  its  outer  and  posterior  border  is  a  flattened  body, 
which  follows  the  course  of  the  testicle,  and  extends  from  its 
upper  to  its  lower  extremity;  this  body  is  named  from  its  relation 
to  the  testis  epididymis  (ixi,  upon,  8t'8v^o$,  the  testicle) ;  it  is 
divided  into  a  central  part  or  body,  an  upper  extremity  or  globus 
major,  and  a  lower  extremity,  globus  minor  (cauda)  epididymis. 
The  globus  major  is  situated  against  the  upper  end  of  the  testicle, 
to  which  it  is  closely  adherent;  the  globus  minor  is  placed  at  its 
lower  end,  is  attached  to  the  testis  by  cellular  tissue,  and  curves 
upwards  to  become  continuous  with  the  vas  deferens. 

The  testis  is  invested  by  three  tunics,  tunica  vaginalis,  tunica 
albuginea,  and  tunica  vasculosa;  and  is  connected  to  the  inner 
surface  of  the  dartos  by  a  large  quantity  of  extremely  loose  cellu- 
lar tissue,  in  which  fat  is  never  deposited,  but  which  is  very  sus- 
ceptible of  serous  infiltration. 

The  tunica  vaginalis  is  a  pouch  of  serous  membrane  derived 
from  the  peritoneum  in  the  descent  of  the  testis,  and  afterwards 
obliterated,  from  the  abdomen  to  within  a  short  distance  of  the 
gland.  Like  other  serous  coverings,  it  is  a  shut  sac,  investing 
the  organ,  and  thence  reflected  so  as  to  form  a  bag  around  its 

40* 


4H  THE   DISSECTOR. 

circumference;  hence  it  is  divided  into  the  tunica  vaginalis  pro- 
pria, and  tunica  vaginalis  reflexa.  The  tunica  vaginalis  propria 
covers  the  surface  of  the  tunica  albuginea,  and  surrounds  the  epi- 
didymis,  connecting  it  to  the  testis  by  means  of  a  distinct  dupli- 
cature.  The  tunica  vaginalis  reflexa  is  attached  by  its  external 
surface,  through  the  medium  of  a  quantity  of  loose  cellular  tissue, 
to  the  inner  surface  of  the  dartos.  Between  the  two  layers  is  the 
smooth  surface  of  the  shut  sac,  moistened  by  its  proper  secretion. 

The  tunica  albuginea  (dura  mater  testis)  is  a  thick  fibrous 
membrane  of  a  bluish  white  color,  and  the  proper  tunic  of  the 
testicle.  It  is  adherent  externally  to  the  tunica  vaginalis  propria, 
and,  from  the  union  of  a  serous  with  a  fibrous  membrane,  is  con- 
sidered to  be  a  fibro-serous  membrane,  like  the  dura  mater  and 
pericardium.  After  surrounding  the  testicle,  the  tunica  albuginea 
is  reflected  from  its  posterior  into  the  interior  of  the  gland,  and 
forms  a  projecting  longitudinal  ridge,  which  is  called  the  medias- 
tinum testis  (corpus  Highmorianum1),  from  which  numerous 
fibrous  cords  (trabeculas,  septula)  are  given  off  to  be  inserted  into 
the  inner  surface  of  the  tunic.  The  mediastinum  serves  to  con- 
tain the  vessels  and  ducts  of  the  testicle  in  their  passage  into  the 
substance  of  the  organ ;  and  the  fibrous  cords  are  admirably  fitted, 
as  has  been  shown  by  Sir  Astley  Cooper,  to  prevent  compression 
of  the  gland.  If  a  transverse  section  be  made  of  the  testis,  and 
the  surface  of  the  mediastinum  examined,  it  will  be  observed  that 
the  bloodvessels  of  the  substance  of  the  organ  are  situated  near 
the  posterior  border  of  the  mediastinum,  while  the  divided  ducts 
of  the  rete  testis  occupy  a  place  nearer  the  free  margin. 

The  tunica  vasculosa  (pia  mater  testis)  is  the  nutrient  mem- 
brane of  the  testis.  It  is  situated  immediately  within  the  tunica 
albuginea,  and  incloses  the  substance  of  the  gland,  sending  pro- 
cesses inwards  between  the  lobules,  in  the  same  manner  that  the 
pia  mater  is  reflected  between  the  convolutions  of  the  brain. 

The  substance  of  the  testis  consists  of  numerous  conical  flattened 
lobules  (lobuli  testis),  the  bases  being  directed  towards  the  surface  of  the 
organ,  and  the  apices  towards  the  mediastinum.  Krause  found  between 
four  and  five  hundred  of  these  lobules  in  a  single  testis.  Each  lobule  is 
invested  by  a  distinct  sheath  formed  of  two  layers,  one  being  derived  from 
the  tunica  vasculosa,  the  other  from  the  tunica  albuginea.  The  lobule 
is  composed  of  one  or  several  minute  tubuli,  tubuli  seminiferi,2  exceedingly 
convoluted,  anastomosing  frequently  with  each  other  near  their  extremi- 


1  Nathaniel  Highmore,  a  physician  of  Oxford,  in  his  "  Corporis  Human! 
Disquisitio  Anatomica,"  published  in  1651,  considers  the  corpus  Highmo- 
rianum as  a  duct  formed  by  the  convergence  of  the  fibrous  cords,  which 
he  mistakes  for  smaller  ducts. 

2  Lauth  estimates  the  whole  number  of  tubuli  seminiferi  in  each  testis 
at  840,  and  their  average  length  at  2  feet  3  inches.     According  to  this 
calculation,  the  whole  length  of  the  tubuli  seminiferi  would  be  1890  feet. 


TESTE8. 


475 


ties,  terminating  in  loops  or  in  free  caecal  ends,  and  of  the  same  diameter 
(ylfl  of  an  inch,  Lauth)  throughout.  The  tubuli  seminiferi  are  of  a  bright 
yellow  color ;  they  become  less  convoluted  in  the  apices  of  the  lobules, 
and  terminate  by  forming  between  twenty  and  thirty  small  straight  ducts 
of  about  twice  the  diameter  of  the  tubuli  seminiferi,  the  vasa  recta.  The 
vasa  recta  enter  the  substance  of  the  mediastinum,  and  terminate  in  from 
seven  to  thirteen  ducts,  smaller  in  diameter  than  the  vasa  recta.  These 
ducts  pursue  a  waving  course  from  below  upwards  through  the  fibrous 
tissue  of  the  mediastinum ;  they  communicate  freely  with  each  other,  and 
constitute  the  rete  testes.  At  the  upper  extremity  of  the  mediastinum,  the 
ducts  of  the  rete  testes  terminate  in  from  nine  to  thirty  small  ducts,  the 
vasa  efferentia, '  which  form  by  their  convolutions  a  series  of  conical  masses, 
the  coni  vasculosi;  from  the  bases  of  these  cones  tubes  of  larger  size  proceed, 
which  constitute,  by  their  complex  convolutions,  the  body  of  the  epidi- 
dymis.  The  tubes  become  gradually  larger  towards  the  lower  end  of  the 
epididymis,  and  terminate  in  a  single  large  and  convoluted  duct,  the  vas 
deferens. 


Fig.  142. 


THE  ANATOMY  OP  THE  TESTICLE. — 

I.  The   tunica  albuginea.      2.   The 
mediastinum  testis,  or  corpus  High- 
raorianum.    3.  A  fibrous  cord  passing 
between  two  of  the  lobules  from  the 
mediastinum  to  the  inner  surface  of 
the  tunica  albuginea.     Similar  cords 
are  observed  between  the  other  lo- 
bules.     4.    The  tunica  vasculosa  or 
pia  mater  testis.     5.  Two  of  the  lo- 
bules of  which  the  substance  of  the 
testicle  is  composed.     They  are  seen 
to  consist  of  the  convolutions  of  mi- 
nute tubes,  tubuli  seminiferi.    6.  The 
small    straight    tubes   by   which   the 
tubuli  seminiferi  terminate,  vasa  rec- 
ta.    7.  The  rete  testis,  an  aggregation 
of  tubuli  situated  in  the  anterior  half 
of  the  mediastinum       The  posterior 
half  (8)   is  occupied  by  the  arteries 
and  veins.     9,9.  The  vasa  efferentia. 
10.  The  conical  convolutions  of  tubuli 
called  coni  vasculosi.    This  portion  of 
the  organ  being  of  large  size,   and 
situated  externally  to  the  testicle,  is 
the  globus  major  of  the  epididymis. 

I 1 .  The  body  of  the  epididymis.     12. 
The  globus  minor  of  the  epididyrais. 
13.    The  vas  deferens,  ascending  to 
the  external  abdominal   ring.      The 
arrows  mark  the  course  of  the  secre- 
tion along  the  tubes. 


The  epididymis  is  formed  by  the  convolutions  of  the  excretory  seminal 
ducts,  externally  to  the  testis,  and  previously  to  their  termination  in  the 


1  Each  vas  efferens  with  its  cone  measures,  according  to  Lauth,  about 
8  inches.  The  entire  length  of  the  tubes  composing  the  epididymis,  ac- 
cording to  the  same  authority,  is  about  21  feet. 


476  THE   DISSECTOR. 

vas  deferens.  The  more  numerous  convolutions,  and  the  aggregation  of 
the  coni  vasculosi  at  the  upper  end  of  the  organ,  constitute  the  globus 
major ;  the  continuation  of  the  convolutions  downwards  is  the  body,  and 
the  smaller  number  of  convolutions  of  the  single  tube  at  the  lower  ex- 
tremity, the  globus  minor.  The  tubuli  are  connected  together  by  a  very 
delicate  cellular  tissue,  and  are  inclosed  by  the  tunica  vaginalis. 

A  small  convoluted  duct,  of  variable  length,  is  generally  connected 
with  the  duct  of  the  epididymis  immediately  before  the  commencement 
of  the  vas  deferens.  This  is  the  vasculum  aberrans  of  Haller  ;  it  is  attached 
to  the  epididymis  by  the  cellular  tissue  in  which  that  body  is  enveloped. 
Sometimes  it  becomes  dilated  towards  its  extremity,  but  more  frequently 
retains  the  same  diameter  throughout. 

The  vas  deferens  may  be  traced  upwards  from  the  globus  minor 
of  the  epididymis,  along  the  posterior  part  of  the  spermatic  cord, 
and  along  the  spermatic  canal  to  the  internal  abdominal  ring. 
From  the  ring  it  is  reflected  inwards  to  the  side  of  the  fundus  of 
the  bladder,  and  descends  along  its  posterior  surface,  crossing 
the  direction  of  the  ureter,  to  the  inner  border  of  the  vesicula 
seminalis.  In  this  situation  it  becomes  somewhat  larger  in  size, 
and  sacculated,  and  terminates  at  the  base  of  the  prostate  gland 
by  uniting  with  the  duct  of  the  vesicula  seminalis  and  constituting 
the  ejaculatory  duct.  The  ejaculatory  duct,  which  is  thus  formed 
by  the  junction  of  the  duct  of  the  vesicula  seminalis  with  the  vas 
deferens,  passes  forwards  in  the  outer  wall  of  the  sinus  pocularis, 
and  terminates  by  a  slit-like  opening,  close  to  or  just  within  the 
aperture  of  the  sinus. 

FEMALE   PELVIS. 

The  boundaries  of  the  pelvis  in  the  female  are  the  same  as 
those  of  the  male.  The  contents  are — the  bladder,  vagina, 
uterus  with  its  appendages,  and  the  rectum.  Some  portion  of  the 
small  intestine  also  occupies  the  upper  part  of  its  cavity. 

The  bladder  is  in  relation  with  the  ossa  pubis  in  front,  with 
the  uterus  behind  (from  which  it  is  usually  separated  by  a  convo- 
lution of  small  intestine),  and  with  the  neck  of  the  uterus  and 
vagina  beneath.  The  form  of  the  female  bladder  corresponds 
with  that  of  the  pelvis,  being  broad  from  side  to  side,  and  often 
bulging  more  on  one  side  than  on  the  other.  This  is  particu- 
larly evident  after  frequent  parturition.  The  coats  of  the  bladder 
are  the  same  as  those  of  the  male. 

The  urethra,  about  an  inch  and  a  half  in  length,  is  lodged  in 
the  upper  and  anterior  wall  of  the  vagina,  in  its  course  down- 
wards and  forwards,  beneath  the  arch  of  the  pnbes,  to  the  meatus 
urinarius.  It  is  lined  by  mucous  membrane  disposed  in  longi- 
tudinal folds,  and  is  continuous,  internally  with  that  of  the  blad- 
der, and  externally  with  that  of  the  vulva.  The  mucous  mem- 
brane is  surrounded  by  a  proper  coat  of  elastic  tissue  (to  which 


FEMALE  PELVIS.  47T 

the  muscular  fibres  of  the  detrusor  urinae  are  attached),  by  a 
plexus  of  bloodvessels,  and  by  the  fibres  of  the  compressor 
urethras.  It  is  to  the  elastic  tissue  that  is  due  the  remarkable 

Fig.  144. 


A  SIDE  VIEW  OP  THE  VISCERA  OP  THE  FEMALE  PELVIS. — 1.  The  sym- 
physis  pubis ;  to  the  upper  part  of  which  the  tendon  of  the  rectus  muscle  is 
attached.  2.  The  abdominal  parietes.  3.  The  collection  of  x'at,  forming  the 
projection  of  the  mons  Veneris.  4.  The  urinary  bladder.  5.  The  entrance  of 
the  left  ureter.  6.  The  canal  of  the  urethra,  converted  into  a  mere  fissure  by 
the  contraction  of  its  walls.  7.  The  meatus  urinarius.  8.  The  clitoris,  with 
its  praeputium,  divided  through  the  middle.  9.  The  left  nympha.  10.  The 
left  labium  majus.  11.  The  meatus  of  the  vagina,  narrowed  by  the  contraction 
of  its  sphincter.  12.  The  canal  of  the  vagina,  upon  which  the  transverse  rugae 
are  apparent.  13.  The  thick  wall  of  separation  between  the  base  of  the  bladder 
and  the  vagina.  14.  The  wall  of  separation  between  the  vagina  and  rectum. 
15.  The  perineum.  16.  The  os  uteri.  17.  Its  cervix.  18.  The  fund  us  uteri. 
The  cavitaa  uteri  is  seen  along  the  centre  of  the  organ.  19.  The  rectum, 
showing  the  disposition  of  its  mucous  membrane.  20.  The  anus.  21.  The 
upper  part  of  the  rectum,  invested  by  the  peritoneum.  22.  The  recto-uterine 
fold  of  the  peritoneum.  23.  The  utero  vesical  fold.  24.  The  reflection  of  the 
peritoneum,  from  the  apex  of  the  bladder,  upon  the  urachus  to  the  internal  sur- 
face of  the  abdominal  parietes.  25.  The  last  lumbar  vertebra.  26.  The  sacrum. 
27.  The  coccyx. 

dilatability  of  the  female  urethra,  and  its  speedy  return  to  its 
original  diameter.  The  meatus  is  encircled  by  a  ring  of  fibrous 
tissue,  which  prevents  it  from  distending  with  the  same  facility 
as  the  rest  of  the  canal ;  hence  it  is  sometimes  advantageous,  in 


478  THE   DISSECTOR. 

performing  this  operation,  to  divide  the  margin  of  the  meatus 
with  the  knife. 

VAGINA. 

The  vagina  is  a  membranous  eanal  leading  from  the  vulva  to 
the  uterus,  and  corresponding  in  direction  with  the  axis  of  the 
outlet  of  the  pelvis.  It  is  constricted  at  its  commencement,  but 
near  the  uterus  becomes  dilated,  and  is  closed  by  the  contact  of 
the  anterior  with  the  posterior  wall.  Its  length  is  variable  ;  but 
it  is  always  longer  upon  the  posterior  than  upon  the  anterior 
wall,  the  former  being  usually  about  five  or  six  inches  in  length, 
and  the  latter  four  or  five.  It  is  attached  to  the  cervix  of  the 
uterus,  which  latter  projects  into  the  upper  extremity  of  the 
canal. 

In  structure  the  vagina  is  composed  of  a  mucous  lining,  a  layer  of 
erectile  tissue,  and  an  external  tunic  of  contractile  fibrous  tissue,  resem- 
bling the  dartos  of  the  scrotum.  The  upper  fourth  of  the  posterior  wall 
of  the  vagina  is  covered,  on  its  pelvic  surface,  by  the  peritoneum ;  while 
in  front  the  peritoneum  is  reflected  from  the  upper  part  of  the  cervix  of 
the  uterus  to  the  posterior  surface  of  the  bladder.  On  each  side  it  gives 
attachment,  superiorly,  to  the  broad  ligaments  of  the  uterus ;  and  infe- 
riorly,  to  the  pelvic  fascia  and  levatores  ani. 

The  mucous  membrane  presents  a  number  of  transverse  papillce  or  rugce, 
upon  the  upper  and  lower  surface  of  the  canal,  the  rugae  extending  out- 
wards on  each  side  from  a  middle  raphe.  The  transverse  papillae  and 
raphe  are  more  apparent  upon  the  upper  than  upon  the  lower  surface, 
and  the  two  raphe  are  called  the  columns  of  the  vagina.  The  mucous 
membrane  is  covered  by  thin  cuticular  epithelium,  which  is  continued 
from  the  labia,  and  terminates  by  a  fringed  border  at  about  the  middle 
of  the  cervix  uteri. 

The  middle,  or  erectile  layer,  consists  of  erectile  tissue  inclosed  be- 
tween two  layers  of  fibrous  membrane  ;  this  layer  is  thickest  near  the 
commencement  of  the  vagina,  and  becomes  gradually  thinner  as  it  ap- 
proaches the  uterus. 

The  external,  or  dartoid  layer  of  the  vagina  serves  to  connect  it  to  sur- 
rounding viscera.  Thus  it  is  very  closely  adherent  to  the  under  surface 
of  the  bladder,  and  drags  that  organ  down  with  it,  in  prolapsus  uteri. 
To  the  rectum  it  is  less  closely  united,  and  that  intestine  is  therefore  less 
frequently  affected  in  prolapsus. 

UTERUS. 

The  uterus  is  a  flattened  organ  of  a  pyriform  shape,  having  the 
base  directed  upwards  and  forwards,  and  the  apex  downwards 
and  backwards  in  the  line  of  axis  of  the  inlet  of  the  pelvis,  and 
forming  a  considerable  angle  with  the  course  of  the  vagina.  It 
is  convex  on  its  posterior  surface,  and  somewhat  flattened  on  its 
anterior  aspect.  In  the  unimpregnated  state  it  is  about  three 
inches  in  length,  two  in  breadth  across  its  broadest  part,  and  one 
in  thickness ;  and  is  divisible  into  fundus,  body,  cervix,  and  os 


UTERUS.  479 

uteri.  At  the  period  of  puberty  the  uterus  weighs  about  one 
ounce  and  a  half;  after  parturition,  from  two  to  three  ounces; 
and  at  the  ninth  month  of  utero-gestation,  from  two  to  four 
pounds. 

Fig.  145. 


THE  FEMALE  INTERNAL  ORGANS  OF  GENERATION. — I.  The  upper  part  of  the 
vagina.  2.  The  os  uteri,  projecting  into  the  vagina ;  the  posterior  lip  is  seen 
to  be  longer  and  larger  than  the  anterior.  3.  The  cervix  uteri.  4.  The  body 
of  the  uterus.  5.  Its  fundus.  6.  The  broad  ligament  of  the  left  side,  having 
inclosed  between  its  layers  (7),  the  Fallopian  tube,  and  (8),  the  round  ligament. 
On  the  right  side  the  broad  ligament  is  removed,  so  as  to  bring  more  clearly 
into  view  the  structures  which  it  contains.  9.  The  Fallopian  tube.  10.  Its 
fimbriated  extremity.  11.  One  of  its  fimbriae  attached  to  the  ovary.  12.  The 
ovary  attached  by  its  ligament  to  the  upper  angle  of  the  uterus.  13.  The  round 
ligament. 

The  fundtis  and  body  are  inclosed  in  a  duplicature  of  perito- 
neum, which  is  connected  with  the  sides  of  the  pelvis,  and  forms 
a  transverse  septum  between  the  bladder  and  rectum.  The  folds 
formed  by  this  duplicatnre  of  peritoneum  on  each  side  of  the 
organ  are  the  broad  ligaments  of  the  uterus. 

The  cervix  is  the  lower  portion  of  the  organ.  It  is  distin- 
guished from  the  body  by  a  well-marked  constriction ;  around 
its  circumference  is  attached  the  upper  end  of  the  vagina  ;  and 
at  its  extremity  is  an  opening  which  is  nearly  round  in  the  virgin, 
and  transverse  after  parturition,  the  os  uteri  (os  tincae),  bounded 
before  and  behind  by  two  labia,  the  anterior  labium  being  the 
most  thick,  and  the  posterior  somewhat  the  longer.  The  opening 
of  the  os  uteri  is  of  considerable  size,  and  is  named  the  orificium 
uteri  externum;  the  canal  then  becomes  narrowed,  and  at  the 
upper  end  of  the  cervix  is  constricted  into  a  smaller  opening, 
the  orificinm  internum.1  At  this  point  the  canal  of  the  cervix 

1  The  orifioium  internum  is  not  unfrequently  obliterated  in  old  persons. 
Indeed,  this  obliteration  is  so  common,  as  to  have  induced  Mayer  to  re- 
gard it  as  normal. 


480  THE  DISSECTOE. 

expands  into  the  shallow  triangular  cavity  of  the  uterus,  the  in- 
ferior angle  corresponding  with  the  orificium  internum,  and  the 
two  superior  angles  (which  are  funnel-shaped  and  represent  the 
original  bicornute  condition  of  the  organ),  with  the  commence- 
ment of  the  Fallopian  tubes.  In  the  canal  of  the  cervix  uteri 
are  two  longitudinal  folds,  anterior  and  posterior  to  which  nu- 
merous oblique  folds  converge  so  as  to  give  the  idea  of  branches 
from  the  stem  of  a  tree ;  hence  this  appearance  has  been  deno- 
minated the  arbor  vitce  uterina.  Between  these  folds  and  around 
the  os  uteri  are  numerous  mucous  follicles.  It  is  the  closure  of 
the  mouth  of  one  of  these  follicles,  and  the  subsequent  disten- 
sion of  the  follicle  with  its  proper  secretion,  that  occasions  those 
vesicular  appearances  so  often  noticed  within  the  mouth  and 
cervix  of  the  uterus,  called  the  ovula  of  Naboth. 

Structure. — The  uterus  is  composed  of  three  tunics :  of  an  external  or 
serous  coat,  derived  from  the  peritoneum,  which  constitutes  the  duplica- 
tures  on  each  side  of  the  organ,  called  the  broad  ligaments  ;  of  a  middle 
or  muscular  coat,  which  gives  thickness  and  bulk  to  the  uterus  ;  and  of 
an  internal  or  mucous  membrane,  which  lines  its  interior,  and  is  continuous 
on  the  one  hand  with  the  mucous  lining  of  the  Fallopian  tubes,  and  on 
the  other  with  that  of  the  vagina. 

In  the  unimpregnated  state  the  muscular  coat  is  exceedingly  condensed 
in  texture,  offers  resistance  to  section  with  the  scalpel,  and  appears  to  be 
composed  of  whitish  fibres  inextricably  interlaced  and  mingled  with 
bloodvessels.  In  the  impregnated  uterus  the  fibres  are  of  large  size, 
distinct,  and  disposed  in  two  layers — superficial  and  deep.  The  superfi- 
cial layer  consists  of  fibres  which  pursue  a  vertical  direction,  some  being 
longitudinal,  and  others  oblique.  The  longitudinal  fibres  are  found 
principally  on  the  middle  line,  forming  a  thin  plane  upon  the  anterior 
and  posterior  face  and  fundus  of  the  organ.  The  oblique  fibres  occupy 
chiefly  the  sides  and  the  fundus.  At  the  angles  of  the  uterus  the  fibres 
of  the  superficial  layer  are  continued  outwards  upon  the  Fallopian  tubes, 
and  into  the  round  ligaments  and  ligaments  of  the  ovaries.  The  deep 
layer  consists  of  two  hollow  cones  of  circular  fibres,  having  their  apex  at 
the  openings  of  the  Fallopian  tubes,  and  intermingling  with  each  other 
by  their  bases  on  the  body  of  the  organ.  These  fibres  are  continuous 
with  the  deep  muscular  layer  of  the  Fallopian  tubes,  and  indicate  the 
primitive  formation  of  the  uterus  by  the  blending  of  these  two  canals. 
Around  the  cervix  uteri  the  muscular  fibres  assume  a  circular  form,  in- 
terlacing with  and  crossing  each  other  at  acute  angles. 

The  mucous  membrane  presents  on  its  surface  numerous  minute  aper- 
tures corresponding  with  mucous  glands,  and  is  provided  with  a  columnar 
ciliated  epithelium,  which  extends  from  the  middle  of  the  cervix  uteri 
to  the  extremities  of  the  Fallopian  tubes. 

Vessels  and  Nerves. — The  arteries  of  the  uterus  are  the  uterine  from  the 
internal  iliac,  and  the  ovarian  from  the  aorta.  The  veins  are  large  and 
remarkable  ;  in  the  impregnated  uterus  they  are  called  sinuses,  and 
consist  of  canals  channelled  through  the  substance  of  the  organ,  being 
merely  lined  by  the  internal  membrane  of  the  veins.  They  terminate 
on  each  side  of  the  uterus  in  the  uterine  plexuses.  The  lymphatics  ter- 
minate in  the  lumbar  glands. 

The  nerves  of  the  uterus  are  derived  from  the  hypogastric  and  sperma- 


FALLOPIAN   TUBES.  481 

tic  plexuses,  and  from  the  sacral  plexus.  They  have  been  made  the 
subject  of  special  investigation  by  Dr.  Robert  Lee,  who  has  successfully 
repaired  the  omission  made  by  Dr.  William  Hunter,  in  this  part  of  the 
anatomy  of  the  organ.  In  his  numerous  dissections  of  the  uterus,  both 
in  the  unimpregnated  and  gravid  state,  Dr.  Lee  has  made  the  discovery 
of  several  large  nervous  ganglia  and  plexuses.  The  principal  of  these, 
situated  on  each  side  of  the  cervix  uteri  immediately  behind  the  ureter, 
he  terms  the  hypogastric  ganglion ;  it  receives  the  greater  number  of  the 
nerves  from  the  hypogastric  and  sacral  plexus,  and  distributes  branches 
to  the  uterus,  vagina,  bladder,  and  rectum.  Of  the  branches  to  the 
uterus,  a  large  fasciculus  proceeds  upwards  by  the  side  of  the  organ 
towards  its  angle,  where  they  communicate  with  branches  of  the  sperma- 
tic plexus,  and  form  another  large  ganglion,  which  he  designates  the 
spermatic  ganglion,  and  which  supplies  the  fundus  uteri.  Besides  these, 
Dr.  Lee  describes  vesical  and  vaginal  ganglia,  and  anterior  and  posterior 
subperitoneal  ganglia  and  plexuses,  which  communicate  with  the  preceding, 
and  constitute  an  extensive  nervous  network  over  the  entire  uterus.  Dr. 
Lee  concludes  his  observations  by  remarking :  "  These  dissections  prove 
that  the  human  uterus  possesses  a  great  system  of  nerves,  which  en- 
larges with  the  coats,  bloodvessels,  and  absorbents  during  pregnancy, 
and  which  returns  after  parturition  to  its  original  condition  before  con- 
ception takes  place.  It  is  chiefly  by  the  influence  of  these  nerves  that 
the  uterus  performs  the  varied  functions  of  menstruation,  conception,  and 
parturition,  and  it  is  solely  by  their  means  that  the  whole  fabric  of  the 
nervous  system  sympathizes  with  the  different  morbid  affections  of  the 
uterus.  If  these  nerves  of  the  uterus  could  not  be  demonstrated,  its 
physiology  and  pathology  would  be  completely  inexplicable."1 

APPENDAGES  OF  THE  UTERUS. 

The  appendages  of  the  uterus  are  inclosed  by  the  lateral  dupli- 
catures  of  peritoneum,  called  the  broad  ligaments.  They  are 
the  Fallopian  tubes  and  ovaries'. 

The  FALLOPIAN  TUBES  or  oviducts,  the  uterine  trumpets  of  the 
French  writers,  are  situated  in  the  upper  border  of  the  broad 
ligaments,  and  are  connected  with  the  superior  angles  of  the 
uterus.  They  are  somewhat  trumpet-shaped,  being  smaller  at 
the  uterine  than  at  the  free  extremity,  and  narrower  in  the  middle 
than  at  either  end.  Each  tube  is  about  four  or  five  inches  in 
length,  and  more  or  less  flexous  in  its  course.  The  canal  of  the 
Fallopian  tube  is  exceedingly  minute ;  its  inner  extremity  opens 
by  means  of  the  o'stium  uterinum  into  the  upper  angle  of  the 
cavity  of  the  uterus,  and  the  opposite  end  into  the  cavity  of  the 
peritoneum.  The  free  or  expanded  extremity  of  the  Fallopian 
tube  presents  a  double  and  sometimes  a  triple  series  of  small 
processes  or  fringes,  which  surround  the  margin  of  the  trumpet  or 
funnel-shaped  opening,  the  ostium  abdominale.  This  fringe-like 
appendage  to  the  end  of  the  tube  has  gained  for  it  the  appella- 
tion of  the  fimbriated  extremity ;  and  the  remarkable  manner  in 

1  Philosophical  Transactions  for  1842. 
41 


482  THE   DISSECTOR. 

which  this  circular  fringe  applies  itself  to  the  surface  of  the  ovary 
during  sexual  excitement,  the  additional  title  of  morsus  diaboli. 
A  short  ligamentous  cord  proceeds  from  the  fimbriated  extremity, 
to  be  attached  to  the  distal  end  of  the  ovary,  and  serves  to  guide 
the  tube  in  its  seizure  of  that  organ. 

The  Fallopian  tube  is  composed  of  three  tunics  :  an  external  and  loose 
investment  derived  from  the  peritoneum ;  a  middle  or  muscular  coat,  con- 
sisting of  circular  [internal]  and  longitudinal  [external]  fibres,  continuous 
with  those  of  the  uterus  ;  and  an  internal  or  lining  mucous  membrane, 
which  is  continuous  on  the  one  hand  with  the  mucous  membrane  of  the 
uterus,  and  at  the  opposite  extremity  with  the  peritoneum.  In  the  minute 
canal  of  the  tube  the  mucous  membrane  is  thrown  into  longitudinal 
folds  or  rugae,  which  indicate  the  adaptation  of  the  tube  for  dilatation. 

The  OVARIES  (testes  muliebres)  are  two  oblong  flattened  and 
oval  bodies  of  a  whitish  color,  and  uneven  surface,  situated  in 
the  posterior  layer  of  peritoneum  of  the  broad  ligaments.  They 
are  connected  to  the  upper  angles  of  the  uterus  at  each  side  by 
means  of  a  rounded  cord,  consisting  of  fibrous  tissue  and  a  few 
muscular  fibres  derived  from  the  uterus — the  ligament  of  the 
ovary.  By  the  opposite  extremity  they  are  connected  by  another 
and  a  shorter  ligament  to  the  fimbriated  aperture  of  the  Fallo- 
pian tube. 

In  structure  the  ovary  is  composed  of  a  cellulo-nbrous  parenchyma  or 
stroma,  traversed  by  bloodvessels,  and  inclosed  in  a  capsule  consisting 
of  three  layers  :  a  vascular  layer,  which  is  situated  most  internally,  and 
sends  processes  inwards  to  the  interior  of  the  organ ;  a  middle  or  fibrous 
layer  (tunica  albuginea)  of  considerable  density ;  and  an  external  invest- 
ment of  peritoneum. 

In  the  cells  of  the  stroma  of  the  ovary  the  small  vesicles  or  ovisacs  of 
the  future  ova,  the  Graafian  vesicles,  are  developed.  There  are  usually 
about  fifteen  fully  formed  Graafian  vesicles  in  each  ovary  ;  and  Dr.  Martin 
Barry  has  shown  that  countless  numbers  of  microscopic  ovisacs  exist  in 
the  parenchyma  of  the  organ,  but  that  very  few  are  perfected  so  as  to 
produce  ova. 

After  conception,  a  yellow  spot,  the  corpus  luteum,  is  found  in  one  or 
both  ovaries.  The  corpus  luteum  is  a  globular  mass  of  yellow  spongy 
tissue,  traversed  by  white  areolar  bands,  and  containing  in  its  centre  a 
small  cavity,  more  or  less  obliterated,  which  was  originally  occupied  by 
the  ovum.  The  interior  of  the  cavity  is  lined  by  a  puckered  membrane, 
the  remains  of  the  ovisac.  In  recent  corpora  lutea,the  opening  by  which 
the  ovum  escaped  from  the  ovisac  through  the  capsule  of  the  ovary  is 
distinctly  visible ;  when  closed,  a  small  cicatrix  may  be  seen  on  the 
surface  of  the  ovary,  in  the  situation  of  the  opening.  A  similar  appear- 
ance to  the  preceding,  but  of  smaller  size,  and  without  a  central  cavity, 
is  sometimes  met  with  in  the  ovaries  of  the  virgin ;  this  is  &  false  corpus 
luteum. 

Vessels  and  Nerves. — The  arteries  of  the  ovaries  are  the  spermatic  or 
ovarian  ;  the  veins  form  an  ovarian  plexus,  which  terminates  in  the  uterine 
plexus.  The  nerves  are  derived  from  the  spermatic  plexus. 

The  ROUND  LIGAMENTS  are  two  muscular  and  fibrous  cords 
between  four  and  five  inches  long,  situated  within  the  layers  of 


EXTERNAL  ORGANS  OF  GENERATION.        483 

the  broad  ligaments,  and  extending  from  the  upper  angles  of  the 
uterus,  and  along  the  spermatic  canals,  to  the  labia  majora,  in 
which  they  are  lost.  They  are  accompanied  by  a  small  artery, 
by  several  filaments  of  the  spermatic  plexus  of  nerves,  by  a  plexus 
of  veins,  and  by  a  process  of  the  peritoneum,  which  represents 
the  serous  membrane  investing  the  spermatic  cord  in  the  male. 
In  the  young  subject,  this  process  extends  for  a  short  distance 
along  the  spermatic  canal,  and  is  denominated  the  canal  of  NucJc; 
it  is  occasionally  pervious  in  the  adult.  The  plexus  of  veins  oc- 
casionally becomes  varicose,  and  forms  a  small  tumor  at  the 
external  abdominal  ring,  which  has  been  mistaken  for  inguinal 
hernia.  The  round  ligaments  serve  to  retain  the  uterus  in  its 
proper  position  in  the  pelvis,  and  during  utero-gestation,  to  draw 
the  anterior  surface  of  the  organ  against  the  abdominal  parietes. 

EXTERNAL  ORGANS  OF  GENERATION. 

The  female  organs  of  generation  are  divisible  into  the  internal 
and  external ;  the  internal  are  contained  within  the  pelvis,  and 
have  been  already  described  ;  they  are  the  vagina,  uterus,  ovaries, 
and  Fallopian  tubes.  The  external  organs  are  the  mons  Veneris, 
labia  majora,  labia  minora,  clitoris,  meatus  urinarius,  and  the 
opening  of  the  vagina. 

The  mons  Veneris  is  the  eminence  of  integument,  situated  upon 
the  front  of  the  ossa  pubis.  Its  cellular  tissue  is  loaded  with 
adipose  substance,  and  the  surface  covered  with  hairs. 

The  labia  majora  are  two  large  longitudinal  folds  of  integument, 
containing  cellular  tissue,  fat,  and  a  tissue  resembling  the  dartos. 
They  inclose  an  elliptical  fissure,  the  common  urino-sexual  open- 
ing or  vulva.  The  vulva  receives  the  inferior  opening  of  the 
urethra  and  vagina,  and  is  bounded,  anteriorly,  by  the  commis- 
sura  superior,  and  posteriorly,  by  the  commissura  inferior. 
Stretching  across  the  posterior  commissure  is  a  small  transverse 
fold,  the  frcennlum  labiorum  or  fourchette,  which  is  ruptured 
during  parturition  ;  and  immediately  within  this  fold  is  a  small 
cavity,  the  fossa  navicularis.  The  length  of  ^ic  perineum  is 
measured  from  the  posterior  commissure  to  the  margin  of  the 
anus,  and  is  usually  not  more  than  an  inch.  The  external  surface 
of  the  labia  is  covered  with  hairs ;  the  inner  surface  is  smooth, 
and  lined  by  mucous  membrane,  which  contains  a  number  of  se- 
baceous follicles,  and  is  covered  by  a  thin  cuticular  epithelium. 
The  use  of  the  labia  majora  is  to  favor  the  extension  of  the  vulva 
during  parturition ;  for,  in  the  passage  of  the  head  of  the  foetus, 
the  labia  are  unfolded  and  completely  effaced. 

The  labia  minora,  or  nympha,  are  two  smaller  folds,  situated 
within  the  labia  raajora.  Superiorly,  they  are  divided  into  two 


484  THE   DISSECTOR. 

processes,  which  surround  the  glans  clitoridis,  the  superior  fold 
forming  the  prseputium  clitoridis,  the  inferior  its  fraenulura.  In- 
feriorly,  they  diminish  gradually  in  size,  and  are  lost  on  the  sides 
of  the  opening  of  the  vagina.  The  nymphae  consist  of  mucous 
membrane,  covered  by  a  thin  cuticular  epithelium.  They  are 
provided  with  a  number  of  mucous  follicles,  and  contain,  in  their 
interior,  a  plexus  of  bloodvessels. 

The  clitoris  is  a  small  elongated  organ,  situated  in  front  of  the 
ossa  pubis,  and  supported  by  a  suspensory  ligament.  It  is 
formed  by  a  small  body,  which  is  analogous  to  the  corpus  caver- 
nosum  of  the  penis,  and  like  it  arises  from  the  ramus  of  the  os 
pubis  and  ischium  on  each  side,  by  two  crura.  At  the  extremity 
of  the  clitoris  is  a  small  accumulation  of  erectile  tissue,  which  is 
highly  sensitive,  and  is  termed  the  glans.  The  corpus  caverno- 
sum  clitoridis,  like  that  of  the  penis,  is  composed  of  erectile  tissue, 
inclosed  in  a  dense  layer  of  fibrous  membrane,  and  is  susceptible 
of  erection.  Like  the  penis,  also,  it  is  provided  with  two  small 
muscles,  the  erectores  clitoridis. 

At  about  an  inch  behind  the  clitoris  is  the  entrance  of  the  vagina, 
an  elliptical  opening,  marked  by  a  prominent  margin.  The  en- 
trance to  the  vagina  is  closed,  in  the  virgin,  by  a  membrane  of  a 
semilunarform,  which  is  stretched  across  the  opening;  this  is  the 
hymen.  Sometimes  the  membrane  forms  a  complete  septum, 
and  gives  rise  to  great  inconvenience  by  preventing  the  escape  of 
the  menstrual  effusion.  It  is  then  called  an  imperf orate  hymen. 
The  hymen  must  not  be  considered  a  necessary  accompaniment  of 
virginity,  for  its  existence  is  very  uncertain.  When  present,  it 
assumes  a  varity  of  appearances  :  it  may  be  a  membranous  fringe, 
with  a  round  opening  in  the  centre  ;  or  a  semilunar  fold;  leaving 
an  opening  in  front ;  or  a  transverse  septum,  having  an  opening 
both  in  front  and  behind ;  or  a  vertical  band  with  an  opening  at 
each  side. 

The  rupture  of  the  hymen,  or  its  rudimentary  existence,  gives 
rise  to  the  appearance  of  a  fringe  of  papillae  around  the  opening 
of  the  vagina;  these  are  the  caruncula  myrtiformes. 

The  triangular  smooth  surface  between  the  clitoris  and  the  en- 
trance of  the  vagina,  which  is  bounded  on  each  side  by  the  upper 
portions  of  the  nymphaB,  is  the  vestibule. 

At  the  posterior  part  of  the  vestibule,  and  near  the  margin  of 
the  vagina,  is  the  opening  of  the  urethra — the  meatus  urinarius  ; 
and  around  the  meatus  an  elevation  of  the  mucous  membrane, 
formed  by  the  aggregation  of  numerous  mucous  glands.  This 
prominence  serves  as  a  guide  to  finding  the  meatus,  in  the  opera- 
tion of  introducing  the  female  catheter. 

Beneath  the  vestibule  on  each  side,  and  extending  from  the 
clitoris  to  the  side  of  the  vagina,  are  two  oblong  or  pyriform 


REGION   OP  THE  BACK.  485 

bodies,  consisting  of  erectile  tissue  inclosed  in  a  thin  layer  of 
fibrous  membrane.  These  bodies  are  narrow  above  (pars  inter- 
media), broad  and  rounded  below,  aud  are  termed  by  Kobelt,  who 
considers  them  analogous  to  the  bulb  of  the  male  urethra,  the 
bulbi  vestibuli. 

Behind  these  bodies,  and  lying  against  the  outer  wall  of  the 
vagina,  are  two  small  glands  analogous  to  Cowper's  glands  in  the 
male  subject ;  these  are  the  glands  of  Bartholine.  Each  gland 
opens,  by  means  of  a  long  duct,  upon  the  inner  side  of  the  corre- 
sponding nympha. 


CHAPTER   X. 

REGION  OF  THE  BACK. 

IT  is  customary  in  most  dissecting-rooms  to  turn  the  body  upon 
its  face  after  the  lapse  of  a  few  days,  that  the  student  may  have 
an  opportunity  of  studying  the  muscles  of  the  back  and  the  pos- 
terior parts  of  the  limbs.  The  student  must  therefore  endeavor 
to  accommodate  his  dissection  to  these  rules.  The  most  appro- 
priate time  for  making  this  dissection  is  when  the  examination  of 
the  front  of  the  shoulder  and  contents  of  the  thorax  has  been 
completed. 

The  region  of  the  back  is,  from  its  extent,  common  to  the  neck, 
the  upper  extremities,  and  the  abdomen.  The  muscles  of  which 
it  is  composed  are  numerous,  and  may  be  arranged  into  six 
layers. 

First  Layer.  Fourth  Layer. 

Trapezius,  (Dorsal  Group.) 

Latissimus  dorsi,  Sacro-lumbahs, 

Longissimus  dorsi, 

Second  Layer.  Spinajis  dorsi. 

Levator  anguli  scapulffi,  (Cervical  Group.) 

Rhomboideus  minor,  Cervicalis  ascendens, 

Rhomboideus  major.  Transversalis  colli, 

Trachelo-mastoideus, 
TJtird  Layer.  Complexus. 

Serratus  posticus  superior,  Btyb  Layer. 

Serratus  posticus  inferior,  (Dorsal  Group.) 

Splenius  capitis,  Semi  spinalis  dorsi, 

Splenius  colli.  Semi  spinalis  colli. 

41* 


486  THE   DISSECTOR. 

(Cervical  Group.)  Sixth  Layer. 

Rectus  anticus  major,  Multifidus  spin*,  ' 

Rectus  anticus  minor,  Inter-spinales, 

Rectus  laterahs,  Inter-transversales. 

Obhquus  inferior,  Levatores  costarum. 
Ubhquus  superior. 

For  the  dissection  of  the  back,  an  incision  should  be  made  along  the 
middle  of  the  spine,  from  the  tubercle  on  the  occipital  bone  to  the  sacrum. 
From  the  upper  extremity  of  this  incision,  carry  a  second  transversely 
outwards  to  the  back  of  the  ear ;  and  from  its  lower  end  a  third,  along 
the  crest  of  the  ilium  to  about  its  middle.  As  the  flap  included  by  these 
incisions  is  too  large  to  be  conveniently  manageable,  a  fourth  incision 
should  be  made  from  the  middle  of  the  back,  transversely  outwards  to 
the  tip  of  the  acromion.  The  two  flaps  should  then  be  dissected  care- 
fully oft  from  the  whole  of  this  surface,  when  the  superficial  fascia  will 
be  exposed. 

The  student  should  now  seek  for  the  superficial  cutaneous  vessels  and 
nerves  of  the  back.  The  former  are  small,  and,  taking  their  course 
usually  in  company  with  the  nerves,  are  useful  as  guides  to  the  situa- 
tion of  the  latter.  The  superficial  cutaneous  nerves  of  the  neck  and 
upper  half  of  the  back  pierce  the  trapezius  close  to  the  spine,  and  pass 
outwards  in  their  distribution  to  the  integument.  Those  of  the  lower 
half  of  the  back  issue  from  the  latissimus  dorsi,  at  a  point  corresponding 
with  the  angle  of  the  ribs  ;  and  those  proceeding  from  the  lumbar  nerves 
reach  the  surface  in  the  situation  of  the  outer  border  of  the  sacro-lum- 
balis. 

The  cutaneous  nerves  of  the  back  are  derived  from  the  posterior 
divisions  of  the  spinal  nerves.  Each  posterior  division  of  a  spinal 
nerve  divides  into  an  internal  and  external  branch.  The  internal 
branch  is  directed  inwards  towards  the  middle  of  the  spine,  and 
becoming  cutaneous  near  the  spinous  processes  of  the  vertebra, 
is  then  reflected  outwards  to  supply  the  integument. 

The  internal  branch  of  the  posterior  division  of  i\\v  first  cervi- 
cal, or  suboccipital  nerve  is  distributed,  when  it  exists,  to  the 
integument  of  the  back  of  the  head. 

The  internal  branch  of  the  posterior  division  of  the  second 
cervical  is  the  occipitalis  major  nerve,  which  pierces  the  origin  of 
the  trapezius  muscle  in  its  course  to  the  back  of  the  head  to  join 
the  occipital  artery. 

The  internal  branch  of  the  third  cervical  nerve,  when  it  arrives 
at  the  surface,  gives  off  a  small  cutaneous  branch  to  the  integu- 
ment of  the  head,  before  it  takes  its  reflected  course  on  the  back 
of  the  neck. 

The  cutaneous  branches  in  the  cervical  region  are  derived  from 
the  third,  fourth,  and  fifth  cervical  nerves  ;  the  internal  branches 
of  the  three  remaining  nerves  being  intended  for  the  supply  of 
the  muscles. 

The  cutaneous  nerves  in  the  thoracic  region  are  derived  :  the 


MUSCLES  OF  THE  BACK.  48f 

st.r  »pper  from  the  internal  branches  of  the  posterior  division  ; 
the  six  lower  from  the  external  branches  of  the  posterior  division. 
The  former  pierce  the  trapezius  near  the  spinous  processes,  and 
are  directed  outwards.  The  latter  pierce  the  latissimus  dorsi 
over  the  angles  of  the  ribs,  and  are  directed  downwards  over  the 
side  of  the  trunk. 

The  cutaneous  nerves,  in  the  lumbar  region,  are  derived  from 
the  external  branches  of  the  posterior  division  of  the  three  upper 
lumbar  nerves ;  they  reach  the  surface  in  a  line  with  the  outer 
border  of  the  sacro-lumbalis,  and  descend  over  the  crest  of  the 
ilium  to  the  integument  of  the  gluteal  region. 

The  cutaneous  nerves  in  the  sacral  region,  derived  from  the 
external  branches  of  the  three  upper  sacral  nerves,  are  distributed 
to  the  integument  of  the  sacral  and  posterior  part  of  the  gluteal 
region  ;  and  those  of  the  last  two  sacral  nerves  to  the  integument 
over  the  coccyx. 

When,  the  cutaneous  nerves  have  been  studied,  the  superficial  fascia 
should  be  removed  from  the  muscles  in  the  direction  of  their  fibres,  and 
the  muscles  of  the  superficial  layer  brought  into  view;  they  are  the 
trapezius  and  latissimus  dorsi. 

FIRST  LAYER. 

The  TRAPEZIUS  muscle  (trapezium,  a  quadrangle  "with  unequal 
sides)  arises  from  the  superior  curved  line  of  the  occipital  bone, 
ligamentum  nucha3,  and  supraspinons  ligament  and  spinous  pro- 
cesses of  the  last  cervical  and  all  the  dorsal  vertebra.  The  fibres 
converge  from  these  various  points,  and  are  inserted  into  the 
scapular  third  of  the  clavicle,  acromion,  and  the  whole  length  of 
the  upper  border  of  the  spine  of  the  scapula.  The  inferior  fibres 
become  tendinous  near  the  scapula,  and  glide  over  the  triangular 
surface  at  the  posterior  extremity  of  its  spine,  upon  a  bursa  mu- 
cosa.  When  the  trapezius  is  dissected  on  both  sides,  the  two 
muscles  resemble  a  trapezium,  or  diamond-shaped  quadrangle,  on 
the  posterior  part  of  the  shoulders :  hence  the  muscle  was  for- 
merly named  cucularis  (cucullus,  a  monk's  oowl).  The  cervical 
and  upper  part  of  the  dorsal  portion  of  the  muscle  is  tendinous 
at  its  origin,  and  forms,  with  the,  muscle  of  the  opposite  side,  a 
Jdnd  of  tendinous  ellipse. 

The  anterior  border  of  the  cervical  portion  of  the  trapezius  forms 
the  posterior  boundary  of  the  posterior  triangle  of  the  neck.  The 
njnn.'il  accessory  nerve,  which  crosses  this  triangle,  passes  beneath 
the  border  of  the  trapezius,  and  is  distributed  to  the  under-sur- 
face  of  the  muscle  as  far  as  its  lower  portion.  There  is  also  con- 
nected with  the  anterior  border  of  the  muscle  in  the  neck  a  small 
artery,  the  superficialis  cervicis,  a  branch  of  the  transversalis  colli. 


488 


THE   DISSECTOR, 
Fig.  146. 


THE  FIRST  AND  SECOND  AND  PART  OF  THE  THIRD  LAYER  OF  MUSCLES  OF 
THE  BACK  ;  THE  FIRST  LAYER  BEING  SHOWN  UPON  THE  RIGHT,  AND  THE 
SECOND  ON  THE  LEFT  SIDE. — 1.  The  trapezius  muscle.  2.  The  tendinous  por- 
tion which,  with  a  corresponding  portion  in  the  opposite  muscle,  forms  the  ten- 
dinous ellipse  on  the  back  of  the  neck.  3.  The  acromion  process  and  spine  of 
the  scapula.  4.  The  latissimus  dorsi  muscle.  5.  The  deltoid.  6.  The  muscles 
of  the  dorsum  of  the  scapula,  infra-spinatus,  teres  minor,  and  teres  major.  7. 
The  external  oblique  muscle.  8.  The  gluteus  medius.  9.  The  glutei  maximi. 
10.  The  levator  anguli  scapulae.  11.  The  rhomboideus  minor.  12.  The  rhom- 
boideus  major.  13.  The  splenius  capitis;  the  muscle  immediately  above,  and 
overlaid  by  the  splenius,  is  the  complexus.  14.  The  splenius  colli,  only  par- 
tially seen  ;  the  common  origin  of  the  splenius  is  seen  attached  to  the  spinous 
processes  below  the  lower  border  of  the  rhomboideus  major.  15.  The  vertebral 
aponeurosis.  16.  The  serratus  posticus  inferior.  17.  The  supra-spinatus  muscle. 
18.  The  infra-spinatus.  19.  The  teres  minor  muscle.  20.  The  teres  major.  21. 
The  long  head  of  the  triceps,  passing  between  the  teres  minor  and  major  to  the 
upper  arm.  22.  The  serratus  magnus,  proceeding  forwards  from  its  origin  at 
the  base  of  the  scapula.  23.  The  internal  oblique  muscle. 


MUSCLES  OF  THE  BACK.  489 

The  trapezius  muscle  should  be  divided  by  a  longitudinal  incision 
directed  along  the  middle  of  the  back,  and  the  two  portions  turned  aside. 
By  turning  the  muscle  back  from  its  cervical  origin,  the  ligamentum 
nuchae  will  be  brought  into  view  ;  and  lower  down,  the  removal  of  the 
muscle  will  enable  the  student  to  see  the  upper  portion  of  the  latissimus 
dorsi. 

The  ligamentum  nuchce  is  a  thin  fibrous  band  extended  from 
the  tubercle  and  spine  of  the  occipital  bone  to  the  spinous  pro- 
cess of  the  seventh  cervical  vertebra,  where  it  is  continuous  with 
the  supraspinous  ligament.  It  is  connected  with  the  spinous  pro- 
cesses of  all  the  cervical  vertebrae,  excepting  the  atlas,  by  means 
of  a  series  of  small  fibrous  slips.  It  is  the  analogue  of  an  im- 
portant elastic  ligament  in  animals. 

The  LATISSIMUS  DORSI  muscle  covers  the  whole  of  the  lower 
part  of  the  back  and  loins.  It  arises  from  the  spinous  processes 
of  the  six  inferior  dorsal  vertebras,  from  all  the  lumbar  and  sacral 
spinous  processes,  from  the  posterior  third  of  the  crest  of  the 
ilium,  and  from  the  three  lower  ribs ;  the  latter  origin  takes  place 
by  muscular  slips,  which  indigitate  with  the  external  oblique 
muscle  of  the  abdomen.  The  fibres  from  this  extensive  origin 
converge  as  they  ascend,  and  cross  the  inferior  angle  of  the 
scapula ;  they  then  curve  around  the  inferior  border  of  the  teres 
major  muscle,  and  terminate  in  a  short  quadrilateral  tendon  which 
lies  in  front  of  the  tendon  of  the  teres  and  is  inserted  into  the 
bicipital  groove.  A  synovial  bnrsa  is  interposed  between  the 
muscle  and  the  lower  angle  of  the  scapula,  and  another  between 
its  tendon  and  that  of  the  teres  major.  The  muscle  frequently 
receives  a  small  fasciculus  from  the  scapula  as  it  crosses  its  inferior 
angle. 

The  latissimus  dorsi  maybe  divided  by  a  longitudinal  incision  directed 
across  the  lower  ribs  to  the  posterior  part  of  the  crest  of  the  ilium,  and 
the  two  portions  of  the  muscle  turned  aside.  In  making  this  dissection, 
care  must  be  taken  to  avoid  injuring  a  small  muscle  which  lies  beneath 
the  serratus  posticus  inferior. 

SECOND  LAYER. 

The  second  layer  of  muscles  consists  of  the  levator  anguli  sca- 
pulae, rhomboideus  minor  and  rhomboideus  major. 

The  LEVATOR  ANGULI  SCAPULAE  arises  by  tendinous  slips,  from 
the  posterior  tubercles  of  the  transverse  processes  of  the  four 
upper  cervical  vertebras,  and  is  inserted  into  the  upper  angle  and 
posterior  border  of  the  scapula,  as  far  as  the  triangular  smooth 
surface  at  the  root  of  its  spine. 

The  RHOMBOIDEUS  MINOR  (rhombus,  a  parallelogram  with  four 
equal  sides)  is  a  narrow  slip  of  muscle,  detached  from  the  rhom- 
boideus major  by  a  slight  cellular  interspace.  It  arises  from  the 
spinous  process  of  the  last  cervical  vertebra  and  ligamentum 


490  THE  DISSECTOR. 

nuchae,  and  is  inserted  into  the  edge  of  the  triangular  surface,  on 
the  posterior  border  of  the  scapula. 

The  RHOMBOIDEUS  MAJOR  arises  from  the  spinous  processes  of 
the  four  upper  dorsal  vertebrae  and  from  the  interspinous  liga- 
ments ;  it  is  inserted  into  the  posterior  border  of  the  scapula  as 
far  as  its  inferior  angle.  The  upper  and  middle  portion  of  the 
insertion  is  effected  by  means  of  a  tendinous  band,  which  is  at- 
tached in  a  longitudinal  direction  to  the  posterior  border  of  the 
scapula. 

The  transversdlis  colli  artery,  a  branch  of  the  thyroid  axis  of 
the  subclavian,  will  be  seen,  at  this  stage  of  the  dissection,  cross- 
ing the  posterior  triangle  of  the  neck,  a  short  distance  above  the 
clavicle,  to  the  levator  anguli  scapulae,  where  it  divides  into  two 
branches,  the  superficialis  cervicis,  which  has  been  already  ex- 
amined in  connection  with  the  anterior  border  of  the  trapezius, 
and  the  posterior  scapular  artery.  The  latter,  which  is  the  proper 
continuation  of  the  transversalis  colli,  passes  beneath  the  levator 
anguli  scapulae  ;  it  then  turns  down  and  runs  along  the  base  of 
the  scapula,  under  cover  of  the  rhomboid  muscles,  to  its  inferior 
angle,  where  it  inosculates  with  the  subscapular  artery.  When 
the  rhomboid  muscles  are  divided  and  turned  aside,  the  artery 
will  be  seen  accompanied  by  a  nerve  (the  rhomboid)  which  dis- 
tributes branches  to  the  levator  anguli  scapulae  and  rhomboidi 
muscles. 

THIRD  LAYER. 

The  third  layer  of  muscles  is  brought  into  view  when  the 
rhomboidei  and  levator  anguli  scapulae  are  divided  through  the 
middle  and  turned  aside.  To  make  them  more  clear,  the  spinous 
attachment  of  the  rhomboid  muscles  may  be  removed  altogether. 
The  third  layer  consists  of  the  serratus  posticus  superior,  serratus 
posticus  inferior,  and  splenius. 

The  SERRATUS  POSTICUS  SUPERIOR  is  situated  at  the  upper  part 
of  the  thorax  ;  it  arises  from  the  ligamentum  nuchae,  the  spinous 
process  of  the  last  cervical  and  those  of  the  two  upper  dorsal 
vertebrae.  The  muscle  passes  obliquely  downwards  and  outwards, 
and  is  inserted  by  four  serrations  into  the  upper  border  of  the 
second,  third,  fourth,  and  fifth  ribs. 

The  SERRATUS  POSTICUS  INFERIOR  arises  from  the  spinous  pro- 
cesses and  interspinous  ligaments  of  the  last  two  dorsal  and  two 
upper  lumbar  vertebrae,  and  passing  obliquely  upwards,  is  inserted 
by  four  serrations  into  the  lower- border  of  the  four  lower  ribs. 
Both  muscles  are  constituted  by  a  thin  aponeurosis  for  about  half 
their  extent. 

The  upper  border  of  the  serratus  posticus  inferior  is  continuous 
with  a  thin  tendinous  layer,  the  vertebral  aponeurosis.  This 


MUSCLES  OF  THE  BACK.  491 

aponeurosis  is  a  thin  membranous  expansion  composed  of  longi- 
tudinal and  transverse  fibres,  and  extending  the  whole  length  of 
the  thoracic  region.  It  is  attached  mesially  to  the  spinous  pro- 
cesses of  the  dorsal  vertebras,  and  externally  to  the  angles  of  the 
ribs ;  superiorly  it  is  continued  upwards  beneath  the  serratus 
posticus  superior,  with  the  lower  border  of  which  it  is  sometimes 
connected.  It  serves  to  bind  down  the  erector  spinae,  and  sepa- 
rate it  from  the  superficial  muscles. 

The  serratus  posticus  superior  must  be  removed  from  its  origin  and 
turned  outwards,  to  bring  into  view  the  whole  extent  of  the  splenius 
muscle. 

The  SPLENIUS  MUSCLE  is  single  at  its  origin,  but  divides  soon 
after  into  two  portions,  which  are  destined  to  distinct  insertions. 
It  arises  from  the  lower  half  of  the  ligamentum  nucha3,  the  spinous 
process  of  the  last  cervical,  and  the  spinous  processes  and  inter- 
spinous  ligaments  of  the  six  upper  dorsal  vertebrae ;  it  divides 
as  it  ascends  the  neck  into  the  splenius  capitis  and  colli.  The 
splenius  capitis  is  inserted  into  the  rough  surface  of  the  occipital 
bone  between  the  two  curved  lines,  and  into  the  raastoid  portion 
of  the  temporal  bone.  The  splenius  colli  is  inserted  into  the  pos- 
terior tubercles  of  the  transverse  processes  of  the  three  or  four 
upper  cervical  vertebrae. 

Returning  to  the  serratus  posticus  inferior,  its  thin  tendon  of 
origin  will  be  found  inseparably  united  with  that  of  the  latissi- 
mus  dorsi,  and  both  are  connected  by  their  under  surface  with 
another  aponeurotic  expansion,  the  fascia  lumborum.  The 
fascia  lumborum  is  the  posterior  aponeurosis  of  the  transversalis 
abdominis  muscle,  and  occupies  the  space  between  the  crest  of 
the  ilium  and '  last  rib  ;  it  also  gives  attachment  to  the  in- 
ternal oblique  muscle  of  the  abdomen,  and  binds  down  the 
lumbar  portion  of  the  large  muscles  of  the  next  layer,  the  erector 
spinae. 

FOURTH  LAYER. 

The  fourth  layer  is  to  be  brought  into  view  by  removing  from 
its  origin  the  splenius  muscle,  and  dividing  and  turning  aside 
the  vertebral  aponeurosis  and  fascia  lumborum.  This  layer  con- 
sists of  the  sacro-lumbalis,  longissimus  dorsi  and  spinalis  dorsi 
in  the  lumbar  and  dorsal  region,  and  the  cervicalis  ascendens, 
transversalis  colli,  trachelo-mastoideus  and  complexus  in  the 
cervical  region. 

The  SACRO-LUMBALIS  and  LONGISSIMUS  DORSI  arise  by  a  com- 
mon origin  from  the  posterior  third  of  the  crest  of  the  ilium, 
from  the  posterior  surface  of  the  sacrum,  and  from  the  lumbar 
vertebrae :  opposite  the  last  rib  a  line  of  separation  begins  to  be 
perceptible  between  the  two  muscles.  The  sacro-lumbalis  is  in- 


492 


THE   DISSECTOR. 


Fig.  147. 


serted  by  separate  tendons  into  the  angles  of  the  six  lower  ribs. 
On  turning  the  muscle  a  little  outwards,  a  number  of  tendinous 
slips  will  be  seen  taking  their  origin  from  the  ribs,  and  termi- 
nating in  a  muscular  fasciculus,  by  which  the  sacro-lumbalis  is 
prolonged  to  the  upper  part  of  the  thorax.  This  is  the  muscnlus 
accessorius  ad  sacro-lumbalem  ;  it  arises  from  the  angles  of  the 
six  lower  ribs,  and  is  inserted  by  separate  tendons  into  the  angles 
of  the  six  upper  ribs. 

The  longissimus  dorsi  is  inserted 
into  the  transverse  processes  of  all 
the  lumbar  and  dorsal  vertebrae,  and 
into  the  six  or  eight  lower  ribs,  be- 
tween their  tubercles  and  angles. 

The  SPINALIS  DORSI  arises  from 
the  spinous  processes  of  the  two 
upper  lumbar  and  two  lower  dorsal 
vertebrae,  and  is  inserted  into  the 
spinous  processes  of  all  the  upper 
dorsal  vertebras.  The  two  muscles 
form  an  ellipse,  which  appears  to 
inclose  the  spinous  processes  of  all 
the  dorsal  vertebrae. 

The  CERVICALIS  ASCENDENS  is  the 
continuation  of  the  sacro-lumbalis 
upwards  into  the  neck.  It  arises 
from  the  angles  of  the  four  upper 
ribs,  and  is  inserted  by  slender  ten- 
dons into  the  posterior  tubercles  of 
the  transverse  processes  of  the  four 
lower  cervical  vertebrae. 

The    TRANSVERSALIS    COLLI  WOllld 

appear  to  be  the  continuation  up- 
wards into  the  neck  of  the  longis- 
simus dorsi ;  it  arises  from  the  trans- 
verse processes  of  the  third,  fourth, 
fifth,  and  sixth  dorsal  vertebrae,  and 
is  inserted  into  the  posterior  tuber- 
cles of  the  transverse  processes  of  the 
four  or  five  inferior  cervical  vertebras. 

THE  FOURTH  AND  FIFTH,  AND  PART  OF  THE  SIXTH  LAYER  OF  THE  MUSCLES 
OF  THE  BACK. — 1.  The  common  origin  of  the  erector  spinae  muscle.  2.  The 
sacro-lumbalis.  3.  The  longissimus  dorsi.  4.  The  spinalis  dorsi.  5.  The 
cervicalis  ascendens.  6.  The  transversalis  colli.  7.  The  trachelo-mastoideus. 
8.  The  complexus.  9.  The  transversalis  colli,  showing  its  origin.  10.  The  semi- 
spinalis  dorsi.  11.  The  semi-spinalis  colli.  12.  The  rectus  posticus  minor. 
13.  The  rectus  posticus  major.  14.  The  obliquus  superior.  15.  The  obliquus 
inferior.  16.  The  multifidus  spinae.  17.  The  levatores  costarum.  18.  Inter- 
transversales.  19.  The  quadratus  lumborum. 


NEEVES   OP  THE   BACK.  493 

The  TRACHELO-MASTOID  is  likewise  a  continuation  upwards 
from  the  longissimus  dorsi.  It  is  a  slender  and  delicate  muscle, 
arising  from  the  transverse  processes  of  the  four  upper  dorsal 
and  four  lower  cervical  vertebrae,  and  inserted  into  the  mastoid 
process  to  the  inner  side  of  the  digastric  fossa. 

The  COMPLEXUS  is  a  large  muscle,  and  with  the  splenius  forms 
the  great  bulk  of  the  back  of  the  neck.  It  crosses  the  direction 
of  the  splenius,  arising  from  the  transverse  processes  of  the 
four  upper  dorsal,  and  from  the  transverse  and  articular  processes 
of  the  four  lower  cervical  vertebrae,  and  is  inserted  into  the  rough 
surface  on  the  occipital  bone  between  the  two  curved  lines,  near 
the  occipital  spine.  A  large  fasciculus  of  the  complexus  is  so 
distinct  from  the  principal  mass  of  the  muscle  as  to  have  led  to 
its  description  as  a  separate  muscle  under  the  name  of  biventer 
cervicis.  This  appellation  is  not  inappropriate,  for  the  muscle 
consists  of  a  central  tendon,  with  two  fleshy  bellies.  The  com- 
plexus is  marked  in  the  upper  part  of  the  neck  by  a  transverse 
tendinous  intersection. 

The  posterior  divisions  of  the  spinal  nerves  and  some  arteries  are 
brought  into  view  with  this  layer.  These  nerves  and  vessels  are  now  to 
be  examined ;  for  which  purpose  the  complexus  should  be  cut  across  its 
middle,  and  its  ends  turned  aside ;  or  so  much  of  the  muscles  removed 
as  may  be  necessary  to  bring  the  next  layer  fully  into  view. 

CERVICAL  NERVES. — The  posterior  divisions  of  the  cervical 
nerves  issue  from  between  the  transverse  processes,  and  divide 
into  an  internal  and  external  branch.  The  internal  branch  is 
directed  inwards  to  the  spinous  processes  of  the  vertebrae,  and 
after  supplying  the  muscles  of  the  inner  portion  of  the  vertebral 
groove  becomes  cutaneous,  and  is  distributed  to  the  infegument 
of  the  neck  (page  486).  The  external  branch  is  smaller  than 
the  internal,  and  is  distributed  to  the  muscles  of  the  outer  portion 
of  the  vertebral  groove. 

There  are  certain  exceptions  to  this  general  idea  of  the  distri- 
bution of  the  posterior  divisions  of  the  cervical  nerves  which 
may  now  be  mentioned. 

The  first,  or  suboccipital  nerve  has  no  external  branch  ;  it 
appears  in  the  space  between  the  recti  and  obliqui  muscles,  and 
is  distributed  to  those  muscles  and  the  complexus.  It  also  sends 
a  branch  downwards  to  communicate  with  the  internal  branch  of 
the  second  cervical  nerve. 

The  internal  branch  of  the  second  cervical  nerve  is  the  occipi- 
talis  major  nerve ;  it  pierces  the  complexus  and  trapezius,  and 
is  distributed  to  the  integumeat  of  the  scalp,  taking  the  direction 
of  the  occipital  artery. 

The  internal  branches  of  the  second,  third,  fourth,  and  fifth 
nerves  lie  upon  the  semispinalis  colli  muscle,  and  are  closely  con- 
42 


494 


THE   DISSECTOR. 
Fig.  148. 


VESSELS  AND  NERVES  OF  THE  BACK  OF  THE  NECK  AND  THORAX. — a. 
The  complexus  muscle,  b,  b.  The  splenius  capitis.  c.  The  splenius  colli.  d. 
The  serratus  posticus  superior,  e.  The  levator  anguli  scapulae.  /.  The  spinalis 
dorsi.  g.  The  longissimus  dorsi.  h.  The  sacro-lumbalis.  i.  The  transversalis 
colli.  k.  The  cervicalis  ascendens.  /.  The  trachelo-mastoideus.  m.  The  rectus 
posticus  minor,  n.  Rectus  posticus  major,  o.  The  transverse  process  of  the 
atlas,  with  the  obliquus  capitis  superior  and  inferior  muscles.  p,  p.  The 
multifidus  spinse  muscle,  q,  q.  The  levatores  costarum.  r,  r.  The  tendons 
of  insertion  of  the  longissimus  dorsi  muscles  into  the  transverse  processes  of 
the  dorsal  vertebrae,  s,  s.  Its  tendons  of  insertion  into  the  ribs,  t,  t.  The 
two  upper  insertions  of  the  sacro-lumbalis  into  the  angles  of  the  ribs,  v, 
v.  The  insertions  of  the  musculus  accessorius  ad  sacro-lumbalem.  iv,  w.  The 
external  intercostal  muscles,  x.  The  spine  of  the  scapula,  y.  The  acromion 
process,  z.  The  mastoid  process.  1,  1.  The  occipital  artery  ;  on  the  left  side 
it  is  seen  giving  oflF  its  princeps  cervicis  branch,  which  descends  near  o  to  inos- 
culate with — 2.  The  profunda  cervicis  artery.  3.  The  vertebral  artery.  4. 
The  transversalis  colli  artery.  5.  Its  superficial  cervicis  branch.  6.  The  pos- 
terior scapular  artery.  7,  7,  8.  The  suprascapular  artery ;  the  upper  7  is  on  the 
clavicle;  the  middle  in  the  supraspinous  fossa;  the  lower  in  the  infraspinous 
fossa ;  below  the  latter  is  the  dorsalis  scapulae  branch  of  the  subscapular  artery. 
9.  The  posterior  auricular  branch  of  the  facial  nerve.  10,  10.  The  occipitalis 
minor  nerve.  11,  11.  The  occipitalis  major.  12.  The  occipital  branch  of  the 
third  cervical  nerve.  13.  The  posterior  division  of  the  first  cervical  nerve. 

14,  14.  The  posterior  divisions  of  the  third,  fourth,  and  fifth  cervical  nerves. 

15,  The   posterior  divisions  of  the  sixth,  seventh,  and  eighth  cervical  nerves. 

16,  16.  The  posterior  divisions  of  the  dorsal  nerves;  each  dividing  into  an  in- 


VESSELS  AND  NERVES  OP  THE  BACK.  495 

nected  with  a  fascia  which  separates  that  muscle  from  the  corn- 
plexus.  The  second  and  third,  with  a  branch  from  the  first, 
constitute  the  posterior  cervical  plexus  ;  and  all  the  branches  in 
their  course  to  the  surface  pierce  the  complexus  and  trapezius 
and  some  the  splenius. 

The  internal  branches  of  the  sixth,  seventh,  and  eighth  nerves 
pass  beneath  the  semispinalis  colli,  and  are  lost  in  the  muscles 
without  reaching  the  integument. 

DORSAL  NERVES. — The  posterior  divisions  of  the  twelve  dorsal 
nerves  appear  between  the  transverse  processes,  and,  like  the 
cervical,  divide  into  an  internal  and  external  branch.  The  in- 
ternal branches  diminish  in  size  from  the  first  to  the  last.  The 
six  upper  branches  pass  inwards  beneath  the  semispinalis  dorsi, 
between  that  muscle  and  the  raultifidus  spina3,  and,  piercing  the 
rhomboid,  trapezius,  and  latissimus  dorsi  muscles,  become  cuta- 
neous close  to  the  spinous  processes,  and  are  reflected  outwards 
to  supply  the  integument  (page  486).  The  six  lower  branches 
are  lost  in  the  muscles  of  the  spine. 

The  external  branches  increase  in  size  from  above  downwards, 
and  make  their  appearance  in  the  line  of  separation  between  the 
longissimus  dorsi  and  sacro-lumbalis.  The  six  upper  branches 
are  distributed  to  those  muscles  and  levatores  costarum.  The 
six  lower,  after  supplying  the  same  muscles,  pierce  the  serratus 
posticus  inferior  and  latissimus  dorsi  in  a  line  with  the  angles  of 
the  vertebra3  and  become  cutaneous  (page  487). 

LUMBAR  NERVES. — The  posterior  divisions  of  these  nerves, 
five  in  number,  also  appear  between  the  transverse  processes  19 
the  muscular  interspace  between  the  longissimus  dorsi  and  multi- 
fidus  spinaB.  Like  the  cervical  and  dorsal  nerves,  they  divide 
into  an  internal  and  external  branch. 

The  internal  branches  are  distributed  to  the  muscles  lying 
close  to  the  spinous  processes,  and  chiefly  to  the  multifidus 
spinas. 

The  external  branches  supply  the  muscles  lying  upon  the  trans- 
verse processes,  and  the  three  upper  pierce  the  aponeurosis  of 
the  latissiraus  dorsi,  and  become  cutaneous  (page  487). 

VESSELS  OF  THE  BACK. — The  arteries  brought  into  view  by  the 
dissection  of  the  deep  muscles  of  the  back,  are — the  princeps 
cervicis,  a  branch  of  the  occipital;  the  vertebral  artery;  the  pro- 
funda  cervicis  ;  and  the  dorsal  branches  of  the  intercostal  and 
lumbar  arteries. 


ternal  and  external  branch,  and  accompanied  by  corresponding  arteries.  17,17. 
The  posterior  cutaneous  branches  of  the  six  upper  dorsal  nerves.  18.  The  pos- 
terior cutaneous  branch  of  the  seventh  dorsal  nerve,  piercing  the  longissimus 
dorsi  muscle. 


496  THE   DISSECTOR. 

The  OCCIPITAL  ARTERY  is  seen  issuing  from  beneath  the  sterno- 
mastoid  and  splenius  muscle  ;  passing  over  the  origin  of  the 
complexus,  and  then  piercing  the  trapezius  in  its  course  to  the 
back  of  the  head. 

The  princeps  cervicis,  a  branch  of  the  occipital,  passes  down- 
wards between  the  complexus  and  semispinalis  colli  muscle,  sup- 
plies the  muscles  in  its  course,  and  inosculates  with  branches  of 
the  vertebral  and  with  the  profunda  cervicis. 

The  VERTEBRAL  ARTERY  is  seen  in  the  space  bounded  by  the 
recti  and  obliqui  muscles ;  where  it  is  making  its  curve  behind 
the  articular  process  of  the  atlas,  previously  to  passing  through 
the  opening  in  the  posterior  occipito-atloid  ligament.  The  sub- 
occipital  nerve  may  also  be  seen  issuing  from  beneath  the  artery. 
The  vertebral  artery  gives  off  a  few  muscular  twigs,  which  inos- 
culate with  the  princeps  cervicis  and  profunda  cervicis. 

The  PROFUNDA  CERVICIS  artery  is  a  branch  of  the  superior  in- 
tercostal of  the  subclavian  :  it  appears  on  the  back  of  the  neck, 
between  the  transverse  processes  of  the  last  cervical  and  first 
dorsal  vertebra,  and  takes  its  course  upwards  between  the  com- 
plexus and  semispinalis  colli.  It  supplies  the  muscles  in  its  way, 
and  inosculates  with  the  princeps  cervicis  and  branches  of  the 
vertebral. 

The  INTERCOSTAL  ARTERIES,  at  the  commencement  of  the  inter- 
costal spaces,  give  off  a  dorsal  branch,  which  passes  backwards, 
between  the  transverse  processes  and  between  the  body  of  the 
vertebra  and  the  anterior  costo-transverse  ligament,  to  the  pos- 
terior aspect  of  the  trunk.  Each  dorsal  branch  accompanies  the 
dorsal  branch  of  the  intercostal  nerve,  and,  like  it,  divides  into 
an  internal  and  extenal  branch,  which  take  a  similar  course  to 
the  branches  of  the  nerve.  The  internal  branch  is  distributed 
to  the  muscles  lying  near  the  spinous  processes,  one  twig  be- 
coming cutaneous  with  the  corresponding  branch  of  the  nerve. 
The  external  branch  supplies  the  longissimus  dorsi,  sacro- 
lumbalis,  and  levatores  costarum  ;  twigs  of  the  lower  dorsal 
branches  becoming  cutaneous  with  the  nerves  which  they  accom- 
pany. 

As  the  dorsal  branch  of  the  intercostal  artery  passes  near  the 
intervetebral  foramen,  it  gives  off  a  spinal  branch,  which  is 
distributed  to  the  membranes  of  the  spinal  cord  and  to  the  ver- 
tebraB. 

The  dorsal  branches  of  the  lumbar  arteries  have  a  similar  dis- 
tribution to  those  of  the  intercostals. 

The  veins  of  the  hack  correspond  with  the  arteries,  and  pass 
forwards,  between  the  transverse  processes  of  the  vertebrae,  to 
open  into  the  vertebral  veins  in  the  neck,  and  the  intercostal  and 
lumbar  veins  in  the  rest  of  the  trunk.  In  the  cervical  regions 


MUSCLES   OP  THE  BACK.  497 

the  veins  are  large  and  communicate  freely,  constituting  a  kind 
of  plexus. 

FIFTH   LAYER. 

The  fifth  layer  consists  of  the  semispinales,  situated  in  the  cer- 
vical and  dorsal  regions,  and  the  small  group  of  recti  and  obliqui 
at  the  upper  part  of  the  cervical  region. 

The  recti  and  obliqui  and  semispinalis  colli  are  already  exposed  by 
the  removal  of  the  muscles  of  the  preceding  layer ;  the  semispinalis  dorsi 
is  brought  into  view  by  the  removal  of  the  longissimus  dorsi  and  spinalis 
dorsi. 

The  SEMISPINALES  muscles  are  connected  with  the  transverse 
and  spinous  processes  of  the  vertebrae,  spanning  one-half  the 
vertebral  column;  hence  their  name  semispinales. 

The  semispinalis  dorsi  arises  from  the  transverse  processes  of 
the  dorsal  vertebras  from  the  sixth  to  the  tenth  ;  and  is  inserted 
into  the  spinous  processes  of  the  four  upper  dorsal  and  two  lower 
cervical  vertebrae. 

The  semispinalis  colli  arises  from  the  transverse  processes 
of  the  five  or  six  upper  dorsal  vertebrae,  and  is  inserted  into  the 
spinous  processes  of  the  cervical  vertebrae  from  the  second  to  the 
fifth. 

The  RECTUS  POSTICUS  MAJOR  arises  from  the  spinous  process 
of  the  axis,  and  is  inserted  into  the  inferior  curved  line  of  the 
occipital  bone. 

The  RECTUS  'POSTICUS  MINOR  arises  from  the  spinous  tubercle 
of  the  atlas,  and  is  inserted  into  the  rough  surface  on  the  occi- 
pital bone,  beneath  the  inferior  curved  line. 

The  RECTUS  LATERALIS  is  extended  between  the  transverse  pro- 
cess of  the  atlas  and  the  occipital  bone ;  it  arises  from  the 
transverse  process  of  the  atlas,  and  is  inserted  into  the  rough  sur- 
face of  the  occipital  bone,  externally  to  the  condyle. 

The  OIILIQUUS  INFERIOR  arises  from  the  spinous  process  of  the 
axis,  and  is  inserted  into  the  extremity  of  the  transverse  process 
of  the  atlas. 

The  OBLIQUUS  SUPERIOR  arises  from  the  extremity,  of  the  trans- 
verse process  of  the  atlas,  and  passes  obliquely  inwards,  to  be 
inserted  into  the  rough  surface  of  the  occipital  bone  between  the 
curved  lines. 

SIXTH  LAYER. 

The  sixth  layer  of  the  muscles  of  the  back  includes  a  muscle 
lying  beneath  the  semispinales,  multifidus  spinae,  the  small 
muscles  passing  between  the  spinous  processes,  others  passing 
between  the  transverse  processes,  and  some  small  muscles  ex- 

42* 


498  THE   DISSECTOR. 

tended  between  the  transverse  processes  and  the  ribs,  the  levatores 
costarum. 

No  other  dissection  is  required  for  the  demonstration  of  these  muscles, 
than  the  removal  of  the  semispinales  and  some  cellular  tissue. 

The  MULTIFIDUS  SPIN^E  consists  of  a  great  number  of  fleshy 
fasciculi  extending  between  the  transverse  and  spinous  processes 
of  the  vertebrae,  from  the  sacrum  to  the  axis.  Each  fasciculus 
arises  from  a  transverse  process,  and  is  inserted  into  the  spinous 
process  of  the  first  or  second  vertebra  above.  The  lowest  fibres 
of  origin  proceed  from  the  sacrum,  and  in  the  lumbar  and  cervi- 
cal regions  from  the  articular  processes.  Some  deep  fasciculi  of 
this  muscle  have  been  described  by  Theile  under  the  name  of 
rotatores  spince. 

The  INTERSPINALES  are  small  muscular  slips  arranged  in  pairs, 
and  situated  between  the  spinous  processes  of  the  vertebrae.  In 
the  cervical  region  there  are  six  pairs  of  these  muscles,  the  first 
being  placed  between  the  axis  and  third  vertebra,  and  the  sixth 
between  the  last  cervical  and  first  dorsal.  In  the  dorsal  region, 
rudiments  of  these  muscles  are  occasionally  met  with  between 
the  upper  and  lower  vertebrae,  but  are  absent  in  the  rest.  In 
the  lumbar  region  there  are  six  pairs  of  interspinales,  the  first 
pair  occupying  the  interspinous  space  between  the  last  dorsal 
and  first  lumbar  vertebra,  and  the  last  the  space  between  the 
fifth  lumbar  and  sacrum.  They  are  thin  and  imperfectly  deve- 
loped. Rudimentary  interspinales  are  occasionally  met  with  be- 
tween the  lower  part  of  the  sacrum  and  the  coccyx;  these  are  the 
analogues  of  the  caudal  muscles  of  brutes ;  in  man  they  have 
been  named  collectively,  the  extensor  coccygus  [sacro-coccygeus 
posticus]. 

The  INTERTRANSVERSALES  are  small  quadrilateral  muscles  situ- 
ated between  the  transverse  processes  of  the  vertebrae.  In  the 
cervical  region  they  are  arranged  in  pairs  corresponding  with  the 
double  conformation  of  the  transverse  processes,  the  vertebral 
artery  and  anterior  division  of  the  cervical  nerves  lying  between 
them.  The  rectus  anticus  minor  and  rectus  lateralis  represent 
the  intertransversales  between  the  atlas  and  cranium.  In  the 
dorsal  region  the  anterior  intertransversales  are  represented  by 
the  intercostal  muscles,  while  the  posterior  are  mere  tendinous 
bands,  muscular  only  between  the  first  and  last  vertebrae.  In 
the  lumbar  region,  the  anterior  intertransversales  are  thin,  and 
occupy  only  part  of  the  space  between  the  transverse  processes. 
Analogues  of  posterior  intertransversales  exist  in  the  form  of 
small  muscular  fasciculi  (interobliqui)  extended  between  the 
rudimentary  posterior  transverse  processes  of  the  lumbar  ver- 
tebrae. 


MUSCLES  OP  THE   BACK.  499 

The  LEVATORES  COSTARUM,  twelve  in  number  on  each  side, 
arise  from  the  tranverse  processes  of  the  dorsal  vertebrae,  and 
pass  obliquely  outwards  and  downwards  to  be  inserted  into  the 
rough  surface  between  the  tubercle  and  angle  of  the  rib  below 
them.  The  first  of  these  muscles  arises  from  the  transverse  pro- 
cess of  the  last  cervical  vertebra,  and  the  last  from  that  of  the 
eleventh  dorsal.  The  levatores  of  the  inferior  ribs,  besides  the 
distribution  here  described,  send  a  fasciculus  downwards  to  the 
second  rib  below  their  origin,  and  consequently  are  inserted  into 
two  ribs:  There  are  four  of  these  levatores  costarum  longi,  for 
the  four  inferior  ribs. 

With  regard  to  the  origin  and  insertion  of  the  muscles  of  the  back, 
the  student  should  be  informed  that  no  exact  regularity  attends  their 
attachments.  At  the  best,  a  knowledge  of  their  precise  connections, 
even  were  it  possible  to  retain  it,  would  be  but  a  barren  information,  if 
not  absolutely  injurions,  as  tending  to  exclude  more  valuable  learning. 
I  have  therefore  endeavoured  to  arrange  a  plan,  by  which  they  may  be 
more  easily  recollected,  by  placing  them  in  a  tabular  form  (p.  500), 
that  the  student  may  see,  at  a  glance,  the  origin  and  insertion  of  each, 
and  compare  the  natural  grouping  and  similarity  of  attachments  of  the 
various  layers.  In  this  manner,  also,  their  actions  will  be  better  com- 
prehended, and  learned  with  greater  facility. 


500 


THE   DISSECTOR. 


ORIGIN. 


Layers. 

Spinous  processes 

Transverse 
processes. 

Ribs. 

Additional. 

1st  Layer. 

Trapezius 

last  cervical,  12 
dorsal 

;. 

•• 

(  occipital  bone,  } 
<    and  ligamen-  > 
(    turn  nuchae     ) 

Latissimus  dorsi     < 

6  lower  dorsal,  5  ) 
lumbar             $ 

.. 

3  lower 

sacrum  and  ilium 

2d  Layer. 

Levator  anguli  sca- 
pulae 

4  upper  cervical 

.. 

.. 

Rhomboideus  min. 

lig.  nuchae,  and 
last  cervical 

.. 

.. 

Rhomboideus  major 

4  upper  dorsal 

.. 

3d  Layer. 

Serratus    posticus 
superior 

lig.  nuchae,   last 
cervical,  2  up- 
per dorsal 

., 

Serratus    posticus  ^ 

2  lower  dorsal,  2 

inferior                  \ 

upper  lumbar 

*  * 

Splenius  capitis 

lig.  iiuchae,  last 

cervical,  6  up- 

• k                       •  • 

*  * 

Splenius  colli 

per  dorsal 

.. 

> 

4th  Layer. 

Sacro  lumbalis 

.  . 

sacrum  and  ilium 

Sacro     accessorius 
ad  sacro-lumba- 
lem 

.. 

.. 

angles  of 
6  lower 

}  •• 

Longissimus  dorsi 

i. 

.. 

•'    1 

sacrum  and  lum-  ) 
bar  vertebrae     5 

Spinalis  dorsi 

2  lower  dorsal,  2 
upper  lumbar 

.. 

.. 

.. 

Cervicalis  ascendens 

.. 

.. 

angles  of 
4  upper 

Transversalis  colli 

.. 

3d,  4th,  5th,  and 
6th  dorsal 

.. 

.. 

Trachelo-mastoideus 

.. 

4  upper  dorsal,  4 
lower  cervical 

.. 

.. 

Complexus 

.. 

4  upper  dorsal,  4 
lower  cervical 

•• 

.. 

5th  Layer. 

Semi-spinalis  dorsi 

.. 

6th  to  10th  dor-  ) 
sal                       I 

•  • 

Semi-spinalis  colli 

.. 

5  or  6  upper  dor-  f 
sal                     j 

Rectus  posticus  maj  . 

axis 

.. 

.. 

Rectus  posticus  min. 

atlas 

Rectus  lateralis 

atlas  ' 

Obliquus  inferior 

axis 

Obliquus  superior 

.. 

axis 

•  • 

.. 

6th  Layer. 

Multifldus  spinse 

..  5 

from  sacrum  to  ) 
3d  cervical       j 

.. 

.. 

Interspinales 

<  cervical    and    \ 
(     lumbar           \ 

.. 

.. 

Intertransversalis 

.. 

cervical      and     \ 
lumbar              j 

.. 

Levatores  costarum 

.. 

last  cervical  and  1 
11  dorsal           j 

•• 

.. 

MUSCLES  OF  THE   BACK. 


501 


I 

NSERTION. 

Spinous  processes. 

Transverse 
processes. 

Ribs. 

Additional. 

.  •              .  • 

.  .        .  . 

.  .          .  .          .. 

f  clavicle  and  spine  of 
\     the  scapula. 

***«'   "        « 

••!.'    '  -V; 

„  ?V.  ->?*";'  '  ..;_ 

fbicipital  groove  of 
(     the  humerus. 

-'•• 

.. 



("angle  and  base  of  the 
\     scapula. 

'-  ..  '       :  '.. 

':'  •.;' 



base  of  the  scapula. 

f" 

.. 



base  of  the  scapula. 

y»  • 

.. 

2d,  3d,  4th,  and  5th. 



I  lower  ribs. 

'-4tt?n"i<-.  •%.. 

4  upper  cervical. 



f  occipital    and   tera- 
\     poral  bone. 

.  . 

.. 

angles  of  6  lower. 

"..  "     \. 

.. 

angles  of  6  upper. 

..     ,'".. 

f  all  the  lumbar 
I     and  dorsal 

(  6  or  8  lower  ribs  be- 
<     tween  tubercles  and 
(     angles. 

8  upper  dorsal. 

4  lower  cervical. 

.. 

4  lower  cervical. 

.. 

.. 

.. 

mastoid  process. 

.. 

.. 

{ 

occipital  bone  between 
the  curved  lines. 

!4  npper  dorsal,  2 
lower  cervical. 
2d   to   5th  cervi- 
cal. 

atlas.' 



occipital  bone, 
occipital  bone, 
occipital  botie. 

occipital  bone. 

{From  last  lumbar 
to  axis, 
cervical  and  lum- 
bar. 

/cervical  and 
\     lumbar. 

f  all  the  ribs  between  the 
|     tubercles  and  angles. 

502  THE   DISSECTOR. 

In  examining  the  foregoing  table,  the  student  will  observe  the  con- 
stant recurrence  of  the  number  four  in  the  origin  and  insertion  of  the 
muscles.  Sometimes  the/owr  occurs  at  the  top  or  bottojn  of  a  region  of 
the  spine,  and  frequently  includes  a  part  of  two  regions,  and  takes  two 
from  each,  as  in  the  case  of  the  serrati.  Again,  he  will  perceive  that  the 
muscles  of  the  upper  half  of  the  table  take  their  origin  from  spinous 
processes,  and  pass  outwards  to  transverse,  whereas  the  lower  half  arise 
mostly  from  transverse  processes.  To  the  student  we  commit  these 
reflections,  and  leave  it  to  the  peculiar  tenor  of  his  own  mind  to  make 
such  arrangements  as  will  be  best  retained  by  his  memory. 

ACTIONS. — The  upper  fibres  of  the  trapezius  draw  the  shoulder  up- 
wards and  backwards  :  the  middle  fibres,  directly  backwards ;  and  the 
lower,  downwards  and  backwards.  The  lower  fibres  also  act  by  produc- 
ing rotation  of  the  scapula  upon  the  chest.  If  the  shoulder  be  fixed,  the 
upper  fibres  will  flex  the  spine  towards  the  corresponding  side.  The 
latissimus  dorsi  is  a  muscle  of  the  arm,  drawing  it  backwards  and  down- 
wards, and  at  the  same  time  rotating  it  inwards ;  if  the  arm  be  fixed, 
the  latissimus  dorsi  will  draw  the  spine  to  that  side,  and,  raising  the 
lower  ribs,  be  an  inspiratory  muscle  ;  and  if  both  arms  be  fixed,  the  two 
muscles  will  draw  the  whole  trunk  forwards,  as  in  climbing  or  walking 
on  crutches.  The  levator  anguli  scapulae  lifts  the  upper  angle  of  the 
scapula,  and  with  it  the  entire  shoulder,  and  the  rhonaboidei  carry  the 
scapula  and  shoulder  upwards  and  backwards. 

The  serrati  are  respiratory  muscles  acting  in  opposition  to  each  other, 
the  serratus  posticus  superior  drawing  the  ribs  upwards,  and  thereby  ex- 
panding the  chest,  and  the  inferior  drawing  the  lower  ribs  downwards, 
and  diminishing  the  cavity  of  the  chest.  The  former  is  an  inspiratory, 
the  latter  an  expiratory  muscle.  The  splenii  muscles  of  one  side  draw 
the  vertebral  column  backwards  and  to  one  side,  and  rotate  the  head 
towards  the  corresponding  shoulder.  The  muscles  of  opposite  sides, 
acting  together,  will  draw  the  head  directly  backwards.  They  are  the 
natural  antagonists  of  the  sterno-mastoid  muscles. 

The  sacro-lumbalis  with  its  accessory  muscle,  the  longissimus  dorsi,  and 
the  spinalis  dorsi,  are  known  by  the  general  term  of  erectores  spince,  which 
sufficiently  expresses  their  action.  They  keep  the  spine  supported  in  the 
vertical  position  by  their  broad  origin  from  below,  and  by  means  of  their 
insertion,  by  distinct  tendons,  into  the  ribs  and  spinous  processes.  Be- 
ing made  up  of  a  number  of  distinct  fasciculi  which  alternate  in  their 
actions,  the  spine  is  kept  erect  without  fatigue,  even  when  they  have  to 
counterbalance  a  corpulent  abdominal  development.  The  continuations 
upwards  of  these  muscles  into  the  neck  preserve  the  steadiness  and 
uprightness  of  that  region.  When  the  muscles  of  one  side  act  alone, 
the  neck  is  rotated  upon  its  axis.  The  complexus,  by  being  attached  to 
the  occipital  bone,  draws  the  head  backwards,  and  counteracts  the  mus- 
cles on  the  anterior  part  of  the  neck.  It  assists  also  in  the  rotation  of 
the  head. 

The  semi-spin  ales  and  multifidus  spince  muscles  act  directly  on  the  ver- 
tebras, and  contribute  to  the  general  action  of  supporting  the  vertebral 
column  erect. 

The  four  little  muscles  situated  between  the  occiput  and  the  first  two 
vertebrae  effect  the  various  movements  between  these  bones,  the  recti 
producing  the  antero-posterior  actions,  and  the  obliqui  the  rotatory  mo- 
tions of  the  atlas  on  the  axis. 

The  actions  of  the  remaining  muscles  of  the  spina — the  interspinales 
and  intertransversales — are  expressed  in  their  names.  They  approximate 


PERINEUM.  503 

their  attachments,  and  assist  the  more  powerful  muscles  in  preserving 
the  erect  position  of  the  body. 

The  levatores  costarum  raise  the  posterior  parts  of  the  ribs,  and  are  pro- 
bably more  serviceable  in  preserving  the  articulation  of  the  ribs  from 
dislocation  than  in  raising  them  in  inspiration. 


CHAPTER    XL 

ANATOMY  OF  THE  PERINEUM. 

THE  perineum  is  the  inferior  part  of  the  trunk  of  the  body,  in 
which  are  situated  the  two  great  excretory  outlets,  the  urethra 
and  the  termination  of  the  alimentary  canal.  These  are  parts  of 
delicate  and  complicated  structure,  and  largely  supplied  with  ves- 
sels and  nerves.  They  are  also  peculiarly  liable,  from  the  nature 
of  their  functions,  to  causes  of  irritation  and  disease.  Indeed, 
disease  is  more  frequent  and  various  in  this  region  than  in  any 
other  of  the  body.  Nearly  the  whole  of  the  affections  admit  of 
relief  or  cure  from  operative  procedure.  Hence  the  perineum 
is  the  most  important  surgical  region  of  the  entire  system,  and 
incisions  are  made  through  it  to  a  great  depth  and  in  various 
directions.  A  good  knowledge  of  its  component  structures  and 
relations  is  therefore  highly  necessary  to  the  surgeon,  for  a  mis- 
directed incision,  by  wounding  important  parts,  would  involve 
the  most  serious  consequences,  and  probably  prove  fatal  to  the 
patient. 

The  anatomical  composition  of  the  perineum  is  the  same  as  that 
of  any  other  part  of  the  body,  consisting  of  integument,  super- 
ficial fascia,  muscles,  vessels,  and  nerves.  But  to  suit  the  pecu- 
liar functions  of  this  region,  they  are  somewhat  differently  distri- 
buted and  arranged. 

To  obtain  a  clear  and  precise  idea  of  the  nature  of  the  perineum, 
the  student  must  take  in  his  hand  a  pelvis  in  which  the  sacro- 
ischiatic  ligaments  have  been  left  in  their  proper  positions.  Let 
him  now  turn  to  the  outlet  of  the  pelvis,  and  he  will  be  enabled- 
to  trace  the  boundaries  of  the  perineum.  In  front  he  will  have  the 
arch  of  the  pubes,  on  each  side  the  ramus  and  tuberosity  of  the 
ischiura  and  great  sacro-ischiatic  ligaments,  and  behind  the  coccyx. 

If  he  draw  a  line  transversely  across  this  outlet  from  the  ante- 
rior extremity  of  one  tuberosity  of  the  ischium  to  the  same  point 
on  the  other,  he  will  divide  the  opening  into  two  parts  of  nearly 
equal  size.  The  anterior  space  belongs  to  the  organs  of  gene- 


504  THE  DISSECTOR. 

ration;  the  posterior,  to  the  termination  of  the  alimentary  canal. 
Let  us  first  examine  the  anterior  or  genital  space. 

A  thin  aponeurosis  is  stretched  across  this  anterior  space,  from 
the  ramus  of  the  pubes  and  ischium  on  one  side,  to  the  same  part 
on  the.  opposite  side.  This  is  the  triangular  ligament.  It  is  a 
septum  of  division  between  the  interior  and  exterior  of  the  pelvis, 
between  the  internal  organs  of  generation  and  the  external. 

Externally  to  the  triangular  ligament  is  the  penis,  whicn  is 
composed  of  two  lengthened  bodies — the  corpus  cavernosum 
above,  and  the  corpus  spongiosum  below.  The  corpus  cavern- 
'osum  is  firmly  attached  to  the  ramus  of  the  pubes  and  ischium 
on  each  side,  by  two  diverging  processes  called  crura  penis.  The 
corpus  spongiosum  is  the  medium  of  transmission  for  the  urethra, 
which  enters  that  body  immediately  on  its  escape  from  the  trian- 
gular ligament,  and  takes  its  course  through  its  interior  to  its 
termination  at  the  meatus  urinarius. 

The  extremity  of  the  corpus  spongiosum,  which  receives  the 
urethra,  is  enlarged,  and  is  called  the  bulb;  at  its  opposite  ex- 
tremity it  is  again  enlarged,  and  forms  the  glans  penis. 

The  penis  is  moved  by  three  pairs  of  muscles,  which  are  the 
muscles  of  the  perineum.  It  is  supplied  with  bloodvessels  and 
nerves  from  the  internal  pudic  artery  and  nerve.  The  muscles, 
vessels,  and  nerves  are  in  immediate  relation  with  the  commence- 
ment of  the  penis,  and  directly  external  to  the  triangular  ligament. 

Then  the  whole  of  these  parts  are  covered  in  and  held  firmly 
in  their  places  by  the  superficial  perineal  fascia,  which  is  con- 
tinuous with  the  triangular  ligament  posteriorly,  and  is  firmly 
attached  on  each  side  to  the  ramus  of  the  pubes  and  ischium, 
whilst,  anteriorly,  it  is  continuous  with  the  cellular  base  of  the 
common  superficial  fascia  of  the  scrotum  and  abdomen. 

So  that  the  genital  portion  of  the  perineum  consists  of  two 
layers  of  aponeurosis,  which  are  connected  posteriorly  and  at  the 
sides,  and  inclose  a  triangular  space,  in  which  are  contained  the 
root  of  the  penis,  with  its  muscles,  vessels,  and  nerves.  Exter- 
nally to  the  superficial  perineal  fascia,  is  the  integument. 

The  posterior  or  anal  portion  of  the  perineum,  instead  of  a  resist- 
ing membranous  partition,  like  the  triangular  ligament,  is  divided 
from  the  cavity  of  the  pelvis  by  a  convex  muscular  septum — the 
levator  ani  muscle,  which  arises  from  nearly  the  whole  circum- 
ference of  the  interior  of  the  pelvis,  and  is  inserted  around  the 
extremity  of  the  rectum.  A  broad  band  of  muscular  fibres  em- 
braces the  lower  end  of  the  intestine,  forming  the  internal  sphinc- 
ter ;  and  superficially  to  it  is  the  flat  ellipse  of  the  external  sphinc- 
ter, which  is  covered  by  the  superficial  fascia  and  integument. 
Externally  to  the  sphincter,  between  it  and  the  internal  wall  of 


PERINEUM.  505 

the  pelvis,  is  the  ischio-rectal  fossa,  which  contains  a  large  collec- 
tion of  fat. 

Dissection. — To  dissect  the  perineum,  the  subject  should  be 
fixed  in  the  position  for  lithotomy,  that  is,  the  hands  should  be 
bound  to  the  soles  of  the  feet,  and  the  knees  kept  apart.  An 
easier  plan  is  the  drawing  of  the  feet  upwards,  by  means  of  a  cord 
passed  through  a  hook  in  the  ceiling.  Both  of  these  means  of 
preparation  have  for  their  object  the  full  exposure  of  the  peri- 
neum. And  as  this  is  a  dissection  which  demands  some  degree 
of  delicacy  and  nice  manipulation,  a  strong  light  should  be  thrown 
upon  the  part.  Having  fixed  the  subject,  and  drawn  the  scrotum 
upwards  by  means  of  a  string  or  hook,  carry  an  incision  from  the 
base  of  the  scrotum  along  the  ramus  of  the  pubes  and  ischium  and 
tuberosity  of  the  ischium,  to  a  point  parallel  with  the  apex  of 
the  coccyx  ;  then  describe  a  curve  over  the  coccyx  to  the  same 
point  on  the  opposite  side,  and  continue  the  incision  onwards 
along  the  opposite  tuberosity  and  ramus  of  the  ischium,  and  ramus 
of  the  pubes,  to  the  opposite  side  of  the  scrotum,  where  the  two 
extremities  may  be  connected  by  a  transverse  incision.  The  in- 
cision will  completely  surround  the  perineum,  following  very 
nearly  the  outline  of  its  boundaries.  Now  let  the  student  dissect 
off  the  integument  carefully  from  the  whole  of  the  included  space, 
and  he  will  expose  the  fatty  cellular  structure  of  the  common 
superficial  fascia. 

The  superficial  fascia  of  the  perineum,  like  that  of  the_  groin, 
consists  of  two  layers,  of  which  the  external  is  cellular,  and 
contains  adipose  tissue  in  variable  proportion ;  and  the  internal 
is  membranous  and  divested  of  fat. 

In  the  superficial  layer  is  contained  a  cutaneous  muscle — the  sphinc- 
ter ani,  which  has  been  already  dissected,  in  the  removal  of  the  integu- 
ment. 

The  SPHINCTER  ANI  is  a  thin  and  elliptical  plane  of  muscle,  closely 
adherent  to  the  integument,  and  surrounding  the  opening  of  the 
anus.  It  arises,  posteriorly,  in  the  superficial  fascia  around  the 
coccyx,  and  by  a  fibrous  raphe  from  the  apex  of  that  bone  ;  and  is 
inserted,  anteriorly,  into  the  tendinous  centre  of  the  perineum,  and 
into  the  raphe  of  the  istegument,  nearly  as  far  forward  as  the 
commencement  of  the  scrotum. 

The  sphincter  ani  may  now  be  turned  back  from  its  anterior  part :  in 
raising  it  some  small  vessels  and  a  nerve  will  be  found  joining  it  from 
the  ischio-rectal  fossa ;  these  are  the  inferior  hemorrhoidal  vessels  and 
nerve.  In  the  next  place  the  student  should  dissect  off  the  superficial  layer 
of  the  superficial  fascia  from  the  deep  layer,  and  pick  out  with  care  all 
the  fat  from  the  ischio-rectal  fossa,  taking  care  to  avoid  injuring  the  deep 
layer  of  the  superficial  fascia,  and  especially  that  portion  of  it  which  turns 
back  to  unite  with  the  triangular  ligament. 

43 


506  THE  DISSECTOR. 

The  deep  or  membranous  layer  of  the  superficial  perineal  fascia 
is  a  strong  but  thin  fibrous  layer,  which  binds  down  the  root  of 
the  penis  and  muscles  of  the  genital  portion  of  the  perineum. 
It  is  firmly  attached  at  each  side  to  the  ramus  of  the  pubes  and 
ischium  nearly  as  far  back  as  the  tuberosities  of  that  bone. 
Across  the  middle  of  the  perineum  it  turns  backwards,  to  become 
continuous  with  the  triangular  ligament.  In  front,  it  is  conti- 
nuous with  the  dartos  of  the  scrotum,  the  superficial  fascia  of  the 
penis,  and  the  deep  layer  of  the  superficial  fascia  of  the  abdomen. 
Moreover,  it  is  connected  on  the  middle  line  with  the  raphe  of 
the  muscles  of  the  spongy  portion  of  the  urethra  and  septum 
scroti,  and  thus  divides  the  perineum  into  two  lateral  cavities, 
more  or  less  complete. 

It  follows,  from  this  arrangement,  that  if  urine  had  escaped 
from  the  urethra  at  the  point  where  that  tube  had  just  traversed 
the  triangular  ligament,  it  would  be  unable  to  follow  the  laws  of 
gravity,  and  pass  backwards  towards  the  anus,  on  account  of  the 
communication  between  the  superficial  perineal  fascia  and  the 
ligament.  It  could  not  pass  outwards  into  the  thighs,  on 
account  of  the  connection  of  the  superficial  perineal  fascia  to  the 
ramus  of  the  pubes  and  ischium.  It  would,  therefore,  burrow 
among  the  muscles  at  the  root  of  the  penis,  and  be  constrained  to 
follow  the  direction  of  the  penis  forwards  into  the  scrotum,  and 
thence  upwards  into  the  cellular  tissue  of  the  lower  part  of  the 
abdomen. 

An  abscess  in  this  situation  is  excessively  painful,  on  account 
of  the  tension  and  resistance  of  the  deep  layer  of  the  superficial 
perineal  fascia;  and,  unless  speedily  opened  by  the  surgeon,  might 
give  rise  to  consequences  dangerous  to  life. 

Behind  the  posterior  and  folded  border  of  the  superficial  fascia, 
is  situated,  at  each  side,  the  ischio-rectal  fossa.  This  fossa  in- 
terposed, as  its  name  implies,  between  the  lower  part  of  the 
rectum,  and  the  side  of  the  ischium,  is  bounded,  in  front,  by  the 
folded  border  of  the  superficial  perineal  fascia  and  triangular 
ligament ;  behind,  by  the  border  of  the  gluteus  maximus  and 
great  sacro-ischiatic  ligament;  internally,  by  the  levator  ani  and 
sphincter  ani ;  and  externally,  by  the  internal  obturator  muscle 
and  obturator  fascia.  In  this,  the  outer  wall  of  the  ischio-rectal 
fossa,  at  a  little  more  than  an  inch  from  the  surface,  and  inclosed 
in  a  special  sheath  of  fascia,  are  the  internal  pudic  vessels  and 
nerve,  and  crossing  the  fossa  to  the  anus,  the  inferior  hemor- 
rhoidal  vessels  and  nerve. 

The  width  of  the  ischio-rectal  fossa  is  about  an  inch,  and  its 
depth  two  inches. 

The  best  manner  of  dissecting  the  superficial  perineal  fascia  is 
to  make  an  incision  from  the  middle  point  of  the  upper  incision 


PERINEUM.  507 

to  the  tuberosity  of  the  ischium  on  each  side.  We  thus  form  a 
A  shaped  flap,  which,  on  being  turned  downwards  (Fig.  153,  -4), 
displays  very  distinctly  the  continuity  of  this  fascia  with  the 
triangular  ligament.  The  two  side  flaps  (5,  5),  are  then  to  be 
dissected  outwards,  and  the  firm  connection  between  this  fascia 
and  the.ramus  of  pubes  and  ischium  demonstrated. 

When  the  student  has  thus  satisfied  himself  of  the  connections 
of  the  superficial  perineal  fascia,  he  must  proceed  to  remove  the 
fat  and  cellular  tissue,  which  conceal  from  view  the  muscles  and 
superficial  vessels  of  the  perineum.  In  the  middle  line  is  the 
projection  of  the  corpus  spongiosum,  and  on  each  side  the  com- 
mencement of  the  corpus  cavernosum  (crus  penis).  Upon  these 
bodies  are  situated  two  pairs  of  muscles;  and,  between  them,  the 
superficial  perineal  vessels  and  nerves  To  see  the  muscles  clearly, 
the  vessels  and  nerves  on  one  side  had  better  be  dissected  away 
with  the  fat  and  cellular  tissue. 

Fig.  149. 


THE  MUSCLES  OP  THE  PERINEUM. — 1.  The  accelerators  urinae  muscles, 
the  figure  rests  upon  the  corpus  spongiosum  penis.  2.  The  corpus  cavernoeum 
of  one  side.  3.  The  erector  penis  of  one  side.  4.  The  transversus  perinei  of 
one  side.  5.  The  triangular  space  through  which  the  deep  perineal  fascia  is 
seen.  6.  The  sphincter  ani;  its  anterior  extremity  is  cut  off.  7.  The  levator 
ani  of  the  left  side  ;  the  deep  space  between  the  tuberosity  of  the  ischium  (8), 
and  the  anus,  is  the  ischio-rectal  fossa ;  the  same  fossa  is  seen  upon  the  opposite 
side.  9.  The  spine  of  the  ischium.  10.  The  left  coccygeus muscle.  The  boun- 
daries of  the  perineum  are  well  seen  in  this  engraving. 

The  MUSCLES  of  the  genital  portion  of  the  perineum,  are 
the— 

Acceleratores  urinse,  Erectores  penis, 

Transversus  perinei. 


508  THE   DISSECTOR. 

The  ACCELERATORES  TIRING;  (bulbo-cavernosi)  arise  from  a 
'tendinous  point  in  the  centre  of  the  perineum,  and  from  the 
fibrous  raphe  of  the  two  muscles.  From  this  origin  the  fibres 
diverge,  like  the  plumes  of  a  pen  ;  the  posterior  fibres,  to  be  in- 
serted into  the  triangular  ligament  and  ramus  of  the  pubes ;  the 
middle,  to  encircle  the  corpus  spongiosum,  and  meet  on  its  upper 
side;  and  the  anterior,  to  spread  out  upon  the  corpus  caver- 
nosum  at  each  side,  and  be  inserted,  partly  into  its  fibrous  struc- 
ture, and  partly  into  the  fascia  of  the  penis.  The  posterior  and 
middle  insertions  of  these  muscles  are  best  seen,  by  carefully 
raising  one  muscle  from  the  corpus  spongiosum  and  tracing  its 
fibres. 

The  ERECTOR  PENIS  (ischio-cavemosus)  arises  from  the  tube- 
rosity  of  the  ischium  and  ramus  of  the  pubes,  and  curves  around 
the  root  of  the  penis,  to  be  inserted  into  the  upper  surface  of 
the  corpus  cavernosum,  where  it  is  continuous  with  a  strong 
fascia  which  covers  the  dorsum  of  the  organ — the  fascia  penis. 

The  TRANSVERSUS  PERINEI  arises  from  the  ramus  of  the  ischium 
on  each  side,  and  is  inserted  into  the  central  tendinous  point  of 
the  perineum. 

A  small  slip  of  muscle  is  sometimes  found  in  front  of  the  transversus 
perinei ;  this  is  the  transversus  perinei  alter.  By  its  inner  end  it  is  con- 
tinuous with  the  accelerator. 

The  three  muscles  above  described  form  the  boundaries  of  a  triangular 
space,  of  which  the  floor  is  constituted,  by  the  triangular  ligament.  The 
space  is  bounded,  internally,  by  the  accelerator  urinse ;  externally,  by 
the  erector  penis ;  and  behind,  by  the  transversus  perinei.  Through 
this  space  the  incision  is  made  in  lithotomy,  and  the  transversus  perinei 
muscle  and  artery  are  cut  across.  The  superficial  perineal  vessels,  which 
occupy  this  space,  are  also  liable  to  be  divided. 

The  muscles  of  the  anal  portion  of  the  perineum,  are  the 
sphincter  ani  external  and  internal,  and  the  levator  ani. 

If  the  external  sphincter  ani  be  raised  at  the  side  as  far  as  its  attach- 
ment to  the  anus,  the  rounded  border  of  the  internal  sphincter  will  be 
brought  into  view. 

The  SPHINCTER  ANI  INTERNUS  is  a  muscular  band  embracing 
the  extremity  of  the  intestine,  and  formed  by  an  aggregation  of 
the  circular  muscular  fibres  of  the  rectum. 

Part  of  the  levator  ani  may  now  be  seen,  forming  the  floor  and  inner 
boundary  of  the  ischio-rectal  fossa.  Its  fibres  may  be  traced  to  their 
insertion  into  the  extremity  of  the  rectum,  and  the  muscle  will  be  seen 
to  be  covered  by  a  thin  fascia.  The  examination  of  the  muscle  in  its 
entire  extent  must  be  left  until  the  pelvis  is  examined  from  within.  It 
arises  within  the  pelvis,  and  is  inserted  into  the  coccyx,  the  raphe  be- 
tween the  coccyx  and  rectum,  the  side  of  the  rectum,  the  central  tendi- 
nous point  of  the  perineum,  and  into  its  fellow  of  the  opposite  side. 

Actions. — The  acceleratores  urinae  being  continuous  at  the  middle 
line,  and  attached  on  each  side  to  the  triangular  ligament  by  means  of 


PERINEUM. 


509 


their  posterior  fibres,  will  support  the  bulbous  portion  of  the  urethra,  and 
acting  suddenly,  will  propel  the  semen,  or  the  last  drops  of  urine  from 

Fig.  150. 


ANATOMY  OF  THE  PERINEUM. — a,  a.  The  testes,  covered  by  cellular  tissue, 
the  scrotum  being  drawn  up.  b.  The  corpus  spongiosum  penis,  e,  c.  The  cor- 
pus cavernosum.  d.  The  acceleratores  urinae  muscles,  e.  The  tendinous  cen- 
tre of  the  perineum.  f,f.  The  slip  of  the  accelerator  urinae,  which  surrounds 
the  corpus  cavernosum.  g,  g.  The  erector  penis  ;  the  letter  is  placed  on  the 
ramus  of  the  ischium.  h,  h.  The  transversus  perinei  muscle ;  the  letter  is 
placed  on  the  tuberosity  of  the  ischium.  *'.  The  sphincter  ani.  k,  k.  The  le- 
vntorani.  I.  The  coccyx,  m^m.  The  gluteus  maximus.  n.  The  origin  of  the 
adductor  lonpus.  o.  The  gracilis.  p.  The  adductor  magnus.  q.  The  con- 
joined head  of  the  biceps  and  semitendinosus.  r,  r.  The  internal  pudic  artery, 
on  the  left  side  accompanied  by  the  pudic  nerve  ;  the  letters  rest  on  the  tuber- 
osity of  the  ischium  ;  the  inferior  hemorrhoidal  arteries  are  seen  crossing  the 
right  ischio-rectal  fossa  (/-)  to  reach  the  surface.  *.  The  internal  pudio  artery 
giving  off  the  artery  of  the  bulb  :  the  small  artery  lying  superficially  to  the 
pudic  at  this  point,  and  then  running  along  the  penis  to  a,  is  the  superficial 
perineal ;  it  is  seen  giving  off  a  transversalis  perinei  branch,  which  crosses  the 
transversus  perinei  muscle  (h)  ;  on  the  left  side  the  nerves  of  the  perineum  are 
principally  shown,  t.  The  hemorrhoidal  branch  of  the  fourth  sacral  nerve,  v,  v. 
The  inferior  pudendal  nerve,  a  branch  of  the  lesser  sciatic,  w.  The  inferior 
hemorrhoidal  nerve  proceeding  from  the  pudic.  x.  The  superficial  perineal 
nerve,  posterior  branch  ;  the  anterior  branch  is  seen  issuing  from  beneath  the 
transversus  perinei  muscle,  and  running  forwards  by  the  side  of  the  posterior 
branch,  in  the  groove  of  the  penis,  to  the  scrotum  at  y. 

43* 


510  THE   DISSECTOR. 

the  canal.  The  posterior  and  middle  fibres,  according  to  Krause,1  con- 
tribute towards  the  erection  of  the  corpus  spongiosum,  by  producing 
compression  of  the  venous  structure  of  the  bulb  ;  and  the  anterior  fibres, 
according  to  Tyrrell,2  assist  in  the  erection  of  the  entire  organ,  by  com- 
pressing the  vena  dorsalis  by  means  of  their  insertion  into  the  fascia 
penis.  The  erector  penis  becomes  entitled  to  its  name  from  spreading 
out  upon  the  dorsum  of  the  organ  into  a  membranous  expansion  (fascia 
penis),  which,  according  to  Krause,  compresses  the  dorsal  vein  during 
the  action  of  the  muscle,  and  especially  after  the  erection  of  the  organ 
has  commenced.  The  transverse  muscles  serve  to  steady  the  tendinous 
centre,  that  the  muscles  attached  to  it  may  obtain  a  firm  point  of  sup- 
port. According  to  Cruveilhier,  they  draw  the  anus  backwards  during 
the  expulsion  of  the  feces,  and  antagonize  the  levatores  ani  which  carry 
the  anus  forwards.  The  external  sphincter,  being  a  cutaneous  muscle, 
contracts  the  integument  around  the  anus,  and  by  its  attachment  to  the 
tendinous  centre  and  to  the  point  of  the  coccyx  assists  the  levator  ani 
in  giving  support  to  the  opening  during  expulsive  efforts .  The  internal 
sphincter  contracts  the  extremity  of  the  cylinder  of  the  intestine. 

Now  that  the  muscles  of  the  perineum  have  been  examined,  the  stu- 
dent should  remove  at  one  side  the  accelerator  urinse,  transversus 
perinei  and  erector  penis,  and  detach  the  crus  penis  from  the  bone ;  he 
will  then  bring  into  view  a  smooth  shining  aponeurotic  layer  which 
forms,  as  it  were,  the  floor  of  the  genital  portion  of  the  perineum.  This  is 
the  external  surface  of  the  triangular  ligament.  By  means  of  the  handle 
of  the  scalpel  it  may  be  traced  to  its  attachment  into  the  ramus  of  the 
pubes  and  ischium  ;  on  the  middle  line  it  is  continuous  with  the  cover- 
ing of  the  penis  behind  the  bulb,  and  below  it  is  continuous  with  the 
folded  border  of  the  superficial  perineal  fascia.  It  is  the  internal 
boundary  of  the  pouch  of  the  genital  portion  of  the  perineum,  which 
contains  the  root  of  the  penis  together  with  its  muscles,  vessels  and 
nerves. 

The  triangular  ligament,  or  deep  perineal  fascia,  is  a  thin  layer 
of  aponeurosis  which  is  stretched  across  the  anterior  portion  of 
the  outlet  of  the  pelvis;  it  is  attached  on  each  side  to  the  pelvic 
border  of  the  ramus  of  the  pubes  and  ischium  as  far  back  as  the 
origin  of  the  erector  penis  muscle.  Anteriorly,  it  is  convex  and 
closely  connected  with  the  subpubic  ligament ;  while,  posteriorly, 
it  is  concave,  and  turns  forwards  around  the  posterior  border  of 
the  transversus  perinei  muscle,  to  become  continuous  with  the 
superficial  perineal  fascia.  At  its  middle,  it  is  about  an  inch  and 
a  half  in  depth ;  at  one  inch  below  the  pubic  arch,  it  is  pierced 
by  the  membranous  portion  of  the  urethra,  and  nearer  the  pubic 
arch,  by  the  dorsal  vein  of  tfye  penis  and  internal  pudic  arteries. 

Directly  behind  the  ligament  are  situated  the  deep  transversus 
perinei  and  compressor  urethra  muscle,  the  arteries  of  the  bulb, 
and  Cowper's  glands,  and  more  deeply  the  pelvic  fascia,  which 
has  been  sometimes  described  as  the  posterior  layer  of  the  trian- 
gular ligament. 

1  Miiller,  Archiv  fiir  Anatomie,  Physiplogie,  £c.,  1837. 
8  Lectures  in  the  College  of  Surgeons.     1839. 


VESSELS  OF  THE  PERINEUM. 


511 


VESSELS  AND  NERVES  OF  THE  PERINEUM. 

The  INTERNAL  PUBIC  ARTERY,  one  of  the  terminal  branches  of 
the  internal  iliac  artery,  in  pursuing  its  course  along  the  inner 
wall  of  the  pelvis,  crosses  the  spine  of  the  ischium.  Hence  it  is 
described  as  passing  out  of  the  pelvis  through  the  great  sacro- 
ischiatic  foramen,  and  re-entering  the  pelvis  through  the  lesser 
sacro-ischiatic  foramen.  It  then  passes  forwards  to  the  ramus  of 
the  ischium,  resting  against  the  obturator  fascia  and  inclosed  in 
a  special  sheath  ;  and  ascends  along  the  inner  border  of  the 

Fig.  151. 


A  DEEPER  DISSECTION  THAN  THAT  REPRESENTED  IN  FIGURE  149,  THE 
I'KIMXKAL  MUSCLES  BEING  REMOVED,  AND  ALSO  THE  FAT  IN  THE  ISCHIO- 
RECTAL  FOSSA. — a.  Superficial  fascia  b.  Accelerator  urinae.  c.  Crus  penis,  d. 
The  bulb.  e.  Triangular  ligament  of  urethra,  f.  Levator  ani.  g.  Sphincter. 
h.  Tuberosity  of  ischium.  k.  Glutneus  maximus.  *  Cowper's  gland  of  the  left 
side.  1.  Pudic  artery.  2.  Superficial  perineal  artery  and  nerve.  The  inferior 
hemorrhoidal  arteries  and  the  artery  of  the  bulb  are  likewise  shown. 

ramus  of  the  ischiura  and  pubes  to  near  .the  arch  of  the  pubes, 
where  it  perforates  the  triangular  ligament  and  divides  into  two 
terminal  branches — the  artery  of  the  corpus  cavernosum  and 
dorsalis  penis.  While  crossing  the  obturator  muscle,  the  artery 
is  situated  in  the  outer  wall  of  the  ischio-rectal  fossa,  at  some- 
what more  than  an  inch  from  the  surface  of  the  tuberosity. 


512 


THE   DISSECTOR. 


The  branches  of  the  internal  pudic  artery  in  the  perineum  are 
the— 

Inferior  heraorrhoidal,          Arteria  corporis  bulbosi, 
Superficialis  perinei,  Arteria  corporis  cavernosi, 

Transversalis  perinei,  Arteria  dorsalis  penis. 

The  inferior  hemorrhoidal  arteries  (external)  are  three  or  four 
small  branches,  given  off  by  the  internal  pudic  while  behind  the 


THE  ARTERIES  OF  THE  PERINEUM;  ON  THE  RIGHT  SIDE  THE  SUPERFICIAL 
ARTERIES  ARE  SEEN,  AND  ON  THE  LEFT  THE  DEEP. — 1.  The  penis,  consisting 
of  corpus  spongiosum  and  corpus  cavernosum.  The  cms  penis  on  the  left  side 
is  cut  through.  2.  The  acceleratores  urinae  muscles,  inclosing  the  bulbous  por- 
tion of  the  corpus  spongiosum.  3.  The  erector  penis,  spreads  out  upon  the 
crus  penis  of  the  right  side.  4.  The  anus  surrounded  by  the  sphincter  ani 
muscle.  5.  The  ram  us  of  the  ischium  and  os  pubis.  6.  The  tuberosity  of  the 
ischium.  7.  The  lessor  sacro-ischiatic  ligament,  attached  by  its  small  extremity 
to  the  spine  of  the  ischium.  8.  The  coccyx.  9.  The  internal  pudic  artery, 
crossing  the  spine  of  the  ischium,  and  entering  the  perineum.  10.  External 
hemorrhoidal  branches.  11.  The  superficialis  perinei  artery,  giving  off  a  small 
branch,  transversalis  perinei,  upon  the  transversus  perinei  muscle.  12.  The  same 
artery  on  the  left  side  cutoff.  13.  The  artery  of  the  bulb.  14.  The  two  ter- 
minal branches  of  the  internal  pudic  artery  ;  one  is  seen  entering  the  divided 
extremity  of  the  crus  penis,  the  artery  of  the  corpus  cavernosum  ;  the  other, 
the  dorsalis  penis,  ascends  upon  the  dorsum  of  the  organ. 

tuberosity  of  the  ischium.  They  cross  the  ischio-rectal  fossa, 
and  are  distributed  to  the  anus,  and  to  the  muscles  and  integu- 
ment of  the  anal  region  of  the  perineum. 

The  superficial  perineal  artery  is  given  off  near  the  attach- 
ment of  the  crus  penis  ;  it  pierces  the  connecting  layer  of  the 
superficial  fascia  and  triangular  ligament,  arid  runs  forward  across 
the  transversus  perinei  muscle,  and  along  the  groove  between  the 


NERVES   OP  THE   PERINEUM.  513 

accelerator  urinae  and  erector  penis  to  the  septum  scroti,  upon 
which  it  ramifies  under  the  name  of  arteria  septi.  It  distributes 
branches  to  the  scrotum  and  to  the  perineum  in  its  course  for- 
wards. One  of  the  latter,  larger  than  the  rest,  crosses  the  peri- 
neum, resting  on  the  transversus  perinei  muscle,  and  is  named 
the  transversalis  perinei.  There  are  often  two  superficial  peri- 
nea! arteries. 

The  artery  of  the  bulb  is  given  off  from  the  pudic,  nearly 
opposite  the  opening  for  the  transmission  of  the  urethra  ;  it 
passes  almost  transversely  inwards  behind  the  triangular  liga- 
ment, and  pierces  that  ligament,  to  enter  the  corpus  spongiosum 
at  its  bulbous  extremity.  It  is  distributed  to  the  corpus  spongio- 
sum. 

The  artery  of  the  corpus  cavernosum,  one  of  the  terminal 
branches  of  the  internal  pudic,  pierces  the  crus  penis,  and  runs 
forward  in  the  interior  of  the  corpus  cavernosum,  by  the  side  of 
the  septum  pectiniforme.  It  ramifies  in  the  parenchyma  of  the 
venous  structure  of  the  corpus  cavernosum. 

The  dorsal  artery  of  the  penis  ascends  between  the  two  crura 
and  symphysis  pubis  to  the  dorsum  penis,  and  runs  forward, 
through  the  suspensory  ligament,  in  the  groove  of  the  corpus 
cavernosum,  to  the  glands,  distributing  branches  in  its  course  to 
the  body  of  the  organ  and  integument. 

The  VEINS  of  the  perineum,  excepting  the  dorsal  vein  of  the 
penis,  unite  to  form  the  internal  pudic  vein,  which  follows  the 
course  of  the  artery,  and  terminates  in  the  internal  iliac  vein. 

The  dorsal  vein  of  the  penis,  after  piercing  the  triangular  liga- 
ment just  beneath  the  subpubic  ligament,  divides  into  two  trunks, 
and  terminates  in  the  prostatic  plexus. 

The  NERVES  of  the  perineum  are,  an  hemorrhoidal  branch  from 
the  fourth  sacral  nerve,  the  inferior  pudeudal  nerve  a  branch  of 
the  lesser  ischiatic  nerve,  and  the  pudic. 

The  hemorrhoidal  branch  of  the  fourth  sacral  nerve  issues  from 
between  the  coccygeus  muscle  and  levator  ani,  and  is  distributed 
to  the  muscles  and  integument  behind  the  anus. 

The  inferior  pudendal  nerve  pierces  the  fascia  lata  near  the 
rainus,  and  just  in  front  of  the  tuberosity  of  the  ischium,  and 
passes  forward  in  the  superficial  fascia  of  the  perineum  to  the 
scrotum,  to  which  and  to  the  root  of  the  penis  it  is  distributed. 
In  its  course  it  communicates  with  the  posterior  superficial  pe- 
rineal  nerve. 

The  PUDIC  NERVE  arises  from  the  lower  part  of  the  sacral  plexus, 
and  passes  out  of  the  pelvis  through  the  great  sacro-ischiatic  fora- 
men below  the  pyriformis  muscle.  It  then  follows  the  course  of 
the  internal  pudic  artery  along  the  wall  of  the  ischio-rectal  fossa, 
lying  inferiorly  to  the  artery  and  inclosed  in  the  same  sheath. 


514  THE  DISSECTOR. 


its  origin  it  gives  off  the  inferior  hemorrhoidal  nerve,  and 
in  the  ischio-rectal  fossa  divides  into  a  superior  and  an  inferior 
branch. 

The  inferior  hemorrhoidal  nerve,  often  a  branch  of  the  sacral 
plexus,  passes  through  the  lesser  sacro-ischiatic  foramen,  and 
descends  to  the  termination  of  the  rectum,  to  be  distributed  to 
the  sphincter  ani  and  integument. 

The  dorsalis  penis  nerve,  the  superior  division  of  the  internal 
pudic,  ascends  along  the  posterior  surface  of  the  ramus  of  the 
ischium,  pierces  the  triangular  ligament,  and  accompanies  the 
arteria  dorsalis  penis  to  the  glans,  to  which  it  is  distributed.  At 
the  root  of  the  penis  the  nerve  gives  off  a  cutaneous  branch  which 
runs  along  the  side  of  the  organ,  gives  filaments  to  the  corpus 
cavernosum,  and  with  its  fellow  of  the  opposite  side  supplies  the 
integument  of  the  upper  two-thirds  of  the  penis  and  prepuce. 

The  perineal  nerve,  or  inferior  terminal  branch,  larger  than 
the  preceding,  pursues  the  course  of  the  superficial  perineal  artery 
in  the  perineum,  and  divides  into  cutaneous  and  muscular 
branches.  The  cutaneous  branches  (superficial  perineal),  two 
in  number,  posterior  and  anterior,  enter  the  ischio-rectal  fossa,  and 
pass  forwards  with  the  superficial  perineal  artery,  to  be  distri- 
buted to  the  integument  of  the  perineum,  scrotum,  and  under 
part  of  the  penis.  The  posterior  superficial  perineal  nerve  also 
sends  a  few  filaments  to  the  integument  of  the  anus  and  sphinc- 
ter ani  ;  while  the  anterior  gives  off  one  or  two  twigs  to  the 
levator  ani. 

The  muscular  branches  proceed  from  a  single  trunk  which 
passes  inwards  behind  the  transversus  perinei  muscle  ;  they  are 
distributed  to  the  transversus  perinei,  accelerator  urinso,  and 
erector  penis.  The  perineal  nerve  also  sends  two  or  three  fila- 
ments to  the  corpus  spongiosum. 

The  student  should  now  bring  more  completely  into  view  the  surface 
of  the  triangular  ligament,  for  which  purpose  he  should  divide  the  cor- 
pus spongiosum  at  about  an  inch  in  front  of  the  bulb,  separate  it  from 
the  corpus  cavernosum,  and  turn  it  down.  One  crus  of  the  corpus  cav- 
ernosum has  been  already  cut  through,  so  that  the  penis  may  also  be 
drawn  aside.  When  the  surface  of  the  triangular  ligament  is  fully  ex- 
posed and  cleaned,  he  should  raise  the  triangular  ligament  carefully,  and 
remove  it,  in  order  to  bring  into  view  the  parts  which  lie  behind.  These 
are  a  pair  of  muscles,  the  deep  transversus  perinei  and  compressor 
urethrse,  Cowper's  glands,  the  membranous  portion  of  the  urethra,  and 
the  arteries  of  the  bulb. 

The  TRANSVERSUS  PERINEI  PROFUNDUS  (perinaeus  profundus) 
is  a  thin  muscle  which  arises  from  the  ramus  of  the  pubes  and 
ischium  by  tendinous  fibres,  and  passes  inwards  to  the  anterior 
extremity  of  the  membranous  portion  of  the  urethra,  where  it  is 


COMPRESSOR   URETHRA. 


515 


united,  by  means  of  a  raph£,  with  its  fellow  of  the  opposite  side, 
and  is  also  inserted  into  the  posterior  part  of  the  bulb. 

The  COMPRESSOR  URETHRA  (constrictor  urethra  membranaceae, 
constrictor  isthrai  urethrse)  arises  from  the  upper  and  lower  sur- 
face of  the  anterior  ligament  of  the  bladder,  and  passing  inwards 
towards  the  middle  line,  divides  into  two  fasciculi,  superior  and 
inferior,  which  embrace  the  membranous  portion  of  the  urethra. 
The  superior  fasciculus  is  continued  forwards  to  the  junction  of 
the  crura  penis,  with  which  it  is  connected,  and  backwards  to  the 
prostate  gland,  upon  the  upper  surface  of  which  it  is  spread  out. 
The  inferior  fasciculus  is  continued  directly  into  its  fellow  of  the 
opposite  side,  beneath  the  membranous  portion  of  the  urethra. 
A  third  fasciculus,  closely  united  with  the  two  preceding,  con- 
sists of  circular  fibres,  which  inclose  and  form  a  muscular  sheath 
for  the  membranous  part  of  the  urethra. 


Fig.  153. 


THE  STRUCTURES  CONTAINED  BETWEEN  THE  TWO  LAYERS  OP  THE  DEEP 
PERINEAL  FASCIA. — 1.  The  symphysis  pubis.  2,  2.  The  ramus  of  the  puhis 
and  ischium.  3,  3.  The  tuberosities  of  the  ischia.  4.  A  triangular  portion  of 
the  superficial  fascia  turned  down,  and  shown  to  be  continuous  with  the  deep 
fascia  (6).  5,  5.  Two  portions  of  the  superficial  perineal  fascia,  showing  its 
connection  to  the  minus  of  the  pubis  and  ischium.  6,  6.  The  posterior  layer 
of  the  deep  perineal  fascia,  the  anterior  layer  having  been  removed.  7.  The 
membranous  portion  of  the  urethra  cut  across.  8.  The  superior  fasciculus 
of  the  compressor  urethras  muscle  of  one  side.  9.  The  inferior  fasciculus  of  the 
compressor  urethra.  The  two  fasciculi  (8)  and  (9),  constitute  Guthrie's  muscle 
of  one  side.  10.  The  pubic  portions  of  the  compressor  urethras,  Wilson's 
muscles.  11.  Cowper's  glands,  partly  embraced  by  the  lower  fasciculus  of  the 
compressor  urethrae  muscle.  12.  The  internal  pudic  artery  passing  posteriorly 
to  the  crus  of  the  compressor  urethras.  13.  The  artery  of  the  bulb.  14.  The 
artery  of  the  corpus  cavernosuin.  15.  The  arteria  dorsalis  penis. 


516  THE   DISSECTOR. 

Under  the  name  of  Wilson's  muscles,  a  fourth  fasciculus  has  been 
described  as  descending  vertically  from  the  body  of  the  pubes,  near  the 
symphysis,  to  unite  with  the  superior  fasciculus  of  the  compressor  ure- 
thrae.  This  fasciculus  is  inconstant,  and  its  existence  is  doubtful. 

Actions. — The  transversus  perinei  profundus  draws  the  urethra  and 
the  bulb  backwards  ;  according  to  Santorinus,  it  also  assists  the  accele- 
rator urinae  in  its  action  of  compressing  the  bulb.  The  compressor 
urethras,  taking  its  fixed  point  from  the  ramus  of  the  pubes  and  ischium 
at  each  side,  can,  says  Mr.  Gruthrie,  "compress  the  urethra, so  as  to  close 
it,  I  conceive  completely,  after  the  manner  of  a  sphincter." 

COWPER'S  GLANDS  are  two  small  bodies  of  the  size  and  shape 
of  peas  somewhat  compressed,  situated  beneath  the  membranous 
portion  of  the  urethra,  immediately  behind  the  bulb  and  trian- 
gular ligament,  and  between  the  deep  transversus  perinei  muscle 
and  deep  segment  of  the  compressor  urethras.  The  gland  is 
lobulated  in  structure,  and  furnished  with  an  excretory  duct 
about  an  inch  in  length,  which  passes  forwards  by  the  side  of 
the  urethra,  between  it  and  the  substance  of  the  bulb,  and  ter- 
minates by  opening,  into  the  bulbous  portion  of  the  urethra. 
Each  gland  is  furnished  with  a  small  arterial  twig  from  the  artery 
of  the  bulb. 

The  OPERATION  OF  LITHOTOMY,  which  especially  gives  interest  to  the 
anatomy  of  the  perineum,  requires  the  division  of  the  different  struc- 
tures which  enter  into  its  composition.  An  incision  has  to  be  made 
through  the  perineum  to  the  neck  of  the  bladder.  Another  operation, 
the  puncture  of  the  bladder  through  the  perineum,  is  also  performed 
by  incising  in  the  same  direction  and  through  the  same  parts.  In  his 
second  dissection,  the  student  should  practise  the  former  operation, 
and  afterwards  examine  the  structures  through  which  his  incision 
has  passed,  and  the  liabilities  that  might  ensue  from  proceeding  igno- 
rantly. 

In  lithotomy  the  patient  is  fixed  by  binding  the  palms  of  the  hands 
against  the  soles  of  the  feet,  and  holding  apart  the  knees.  The  operator 
has  thus  the  whole  expanse  of  the  perineum  before  his  eyes  ;  he  observes 
the  elevated  line  (raphe),  which  runs  along  the  middle  of  the  perineum 
to  the  anus,  and  he  feels  for  the  tuberosity  of  the  ischium ;  he  then 
commences  an  incision  at  the  raphe,  about  an  inch  and  a  half,  more  or 
less,  in  front  of  the  anus.  The  exact  point  for  the  commencement  of  the 
incision  must  always  be  left  to  the  judgment  of  the  operator,  who  will 
proportion  the  length  of  his  incision  to  the  size  and  age  of  his  patient, 
his  fatness,  ot  emaciation  ;  an  inch  and  a  half  being  about  the  average 
distance  in  an  adult  of  ordinary  condition. 

The  incision  is  carried  obliquely  downwards  and  outwards,  to  a 
point  one-third  nearer  to  the  tuberosity  of  the  ischium  than  to  the 
anus,  and  should  terminate  opposite  the  middle  of  the  anus.  The  pro- 
portional distance  between  the  tuberosity  of  the  ischium  and  anus,  is 
the  Scylla  and  Charybdis  of  the  operation ;  for  approaching  nearer  the 
former  would  endanger  the  internal  pudic  artery ;  and  the  latter,  the 
rectum ;  particularly  if  the  surgeon  have  neglected  the  precaution  of 
emptying  that  bowel  previously  to  the  operation. 

The  first  step,  then,  of  the  operation  is  to  make  a  steady  incision  from 
the  raphe",  an  inch  and  a  half  in  front  of  the  anus,  obliquely  downwards 


OPERATION   OF   LITHOTOMY.  517 

and  outwards  to  a  point  one-third  nearer  the  tuberosity  of  the  ischium 
tli.-ui  the  anus,  and  opposite  the  middle  of  that  opening.  This  incision 
should  divide  the  integument,  the  superficial  perineal  fascia,  the  lower 
fibres  of  the  accelerator  urinse,  the  transversus  perinei  muscle  and  artery, 
and  some  branches  of  the  inferior  hemorrhoidal  arteries  and  nerve.  It 
may  also  divide  the  superficial  perineal  vessels  and  nerves. 

The  operator  now  inserts  his  finger  into  the  upper  part  of  the  incision, 
drawing  aside  the  bulb  of  the  urethra,  and  presses  his  nail  into  the 
groove  of  the  staff,  just  at  the  point  where  the  urethra  escapes  from  the 
triangular  ligament :  he  then  conveys  the  point  of  a  knife,  guided  by  his 
finger  nail,  into  the  groove  at  the  under  part  of  the  cylinder  of  the  ure- 
thra, and  carries  it  onwards,  along  the  groove  in  the  stalf,  into  the  bladder. 
In  withdrawing  the  knife  he  depresses  the  handle,  so  as  to  divide  but 
slit/htli/  the  neck  of  the  bladder,  prostate  gland,  and  triangular  ligament, 
and  more  extensively  any  of  the  other  textures  which  may  have  re- 
mained undivided  by  the  first  incision. 

The  form  in  the  opening  thus  made  must  evidently  be  triangular,  the 
lias.'  being  at  the  integument,  the  apex  at  the  neck  of  the  bladder.  The 
insertion  of  the  knife  into  the  under  part  of  the  cylinder,  of  the  urethra, 
is  a  precaution  for  avoiding  the  artery  of  the  bulb,1  which  might  other- 
wise be  divided,  and  give  rise  to  unpleasant  hemorrhage. 

The  third  step  of  the  operation  consists  in  introducing  the  finger  of  the 
left  hand  through  the  wound  into  the  bladder,  dilating  the  neck  of 
that  viscus,  and  breaking  the  prostate  gland  in  the  direction  of  the  inci- 
sion, for  the  purpose  of  securing  space  for  the  removal  of  the  calculus. 
Then  passing  the  forceps  along  the  finger,  the  calculus  is  seized  by  its 
short  diameter,  and  must  be  withdrawn  in  the  axis  of  the  pelvis. 

The  structures  cut  through  in  this  operation  in  their  order  of  division, 
are  the — 

Integument, 

Superficial  perineal  fascia, 

Bulbous  portion  of  the  accelerator  urinse  muscle, 

Transversus  perinei  muscle, 

Transversalis  perinei  artery, 

Triangular  ligament, 

Membranous  portion  of  the  urethra, 

Lower  segment  of  the  deep  transversus  perinei  muscle, 

Lower  segment  of  the  compressor  urethras, 

Some  fibres  of  the  levator  ani, 

l'r<  .state  gland, 

Neck  of  the  bladder. 

The  structures  in  the  female  perineum  are  the  same  as  in  the 
male,  but  somewhat  modified  to  suit  the  difference  of  form  in 
the  organs  of  generation.  The  integument  and  superficial  fascia 
are  thrown  into  folds,  called  labia,  to  prepare  for  the  enormous 
distension  to  which  this  part  is  submitted  in  parturition.  The 
entrance  of  the  vagina  is  encircled  by  a  sphincter,  which  is  not 
unlike  the  accelerator  urinoe  of  the  male.  The  clitoris  is  the 
penis  of  the  female,  composed  of  its  corpus  cavernosum,  and 

1  The  author  has  seen  two  or  three  instances  of  the  early  division  of 
this  artery,  in  which  no  precaution  on  the  part  of  the  surgeon  could  have 
availed,  and  the  artery  must  have  been  inevitably  divided. 
44 


518  THE   DISSECTOR. 

therefore  provided  with  erectores  clitoridis,  analogous  to  the  erec- 
tores  penis.  The  transversus  perinei,  sphincters,  and  levator 
ani,  are  precisely  the  same  as  in  the  male. 

The  dissection  of  the  female  perineum  should  be  the  same  as  that 
already  prescribed  for  the  male.  The  integument  having  been  turned 
aside,  the  superficial  fascia  and  superficial  vessels  should  be  examined 
and  removed.  The  labia  majora,  being  composed  of  integument  and 
cellular  tissue,  should  also  be  removed,  and  the  muscles  brought  into 
view,  and  carefully  cleaned. 

The  MUSCLES  of  the  female  perineum  are  the — 
Constrictor  vaginae, 

Transversus  perinei,  superficial  and  deep, 
Erector  clitoridis, 
Compresser  urethras, 
Sphincter  ani. 

The  CONSTRICTOR  VAGINJE  is  analogous  to  the  accelerator 
urinae  of  the  male  :  it  arises  from  the  tendinous  centre  of  the 
perineum,  where  it  is  continuous  with  the  sphincter  ani  and 
transversus  perinei ;  and  passes  forwards  on  each  side  of  the  en- 
trance of  the  vagina,  to  be  inserted  into  the  corpus  cavernosum 
clitoridis. 

The  TRANSVERSUS  PERINEI  is  a  small  muscle  arising  on  each 
side  from  the  ramus  of  the  ischium,  and  inserted  into  the  side  of 
the  constrictor  vaginae. 

The  TRANSVERSUS  PERINEI  PROFUNDUS  is  situated  above  the 
triangular  ligament :  as  in  the  male,  it  is  inserted  into  the  ure- 
thra. 

The  ERECTOR  CLITORIDIS  arises  from  the  ramus  of  the  ischium, 
and  is  inserted  on  each  side  into  the  crus  clitoridis. 

The  COMPRESSOR  URETHRA  has  the  same  origin  and  insertion, 
and  exercises  the  same  functions  in  the  female  as  in  the  male. 

The  SPHINCTER  ANI  surrounds  the  lower  extremity  of  the  rec- 
tum, as  in  the  male. 

The  LEVATOR  ANI  is  inserted  into  the  side  of  the  vagina  and 
rectum. 

The  TRIANGULAR  LIGAMENT  is  the  same  as  in  the  male,  but  of 
less  extent. 

The  VESSELS  and  NERVES  of  the  perineum  are  identical  with 
those  of  the  male,  with  the  exception  that  the  artery  of  the  bulb 
is  distributed  to  the  vagina.  The  nerve  of  the  bulb  has  a  similar 
distribution. 


FCETAL   CIRCULATION.  519 


CHAPTER    XII. 

ANATOMY  OF  THE  F<ETUS. 

THE  medium  weight  of  a  child  of  the  full  period,  at  birth  is 
seven  pounds,  and  its  length  seventeen  inches;  the  extremes  of 
weight  are  four  pounds  and  three-quarters,  and  ten  pounds;  and 
the  extremes  of  measurement,  fifteen  and  twenty  inches.  The 
head  is  of  large  size,  and  lengthened  from  before  backwards ;  the 
face  small.  The  upper  extremities  are  greatly  developed,  and 
the  thorax  expanded  and  full.  The  upper  part  of  the  abdomen 
is  large,  from  the  great  size  of  the  liver;  the  lower  part  is  small 
and  conical ;  and  the  lower  extremities  are  very  small  in  propor- 
tion to  the  rest  of  the  body.  The  external  genital  organs  are 
very  large  and  fully  developed;  and  the  attachment  of  the  umbi- 
licus is  one  inch  further  from  the  vortex  of  the  head  than  from 
the  soles  of  the  feet,  and  one  inch  further  from  the  ensiform  card- 
large  than  from  the  symphysis  pubis. 

OSSEOUS  SYSTEM. — The  development  of  the  osseous  system  is 
treated  of  in  works  on  special  anatomy.  The  ligamentous  system 
presents  no  peculiarity  deserving  of  remark. 

MUSCULAR  SYSTEM. — The  muscles  of  the  foetus  at  birth  are 
large  and  fully  formed.  They  are  of  lighter  color  than  those  of 
the  adult,  and  softer  texture.  The  transverse  striae  on  the  fibres 
of  animal  life,  are  not  distinguishable  until  the  sixth  month  of 
fatal  life. 

VASCULAR  SYSTEM. — The  circulating  system  presents  several 
peculiarities:  1st,  in  the  heart;  there  is  a  communication  between 
the  two  auricles  by  means  of  the  foramen  ovah.  2dly,  in  the 
arterial  system ;  there  is  a  communication  between  the  pulmonary 
artery  and  descending  aorta,  by  means  of  a  large  trunk — the  duc- 
tus  arteriosus.  3dly,  also  in  the  arterial  system ;  the  internal 
iliac  arteries,  under  the  name  of  hypogastric  and  umbilical,  are 
continued  from  the  foetus  to  the  placenta,  to  which  they  return 
the  blood  which  has  circulated  in  the  system  of  the  foetus.  4thly, 
in  the  venous  system;  there  is  a  communication  between  the  um- 
bilical vein  and  the  inferior  vena  cava,  called  the  ductus  venosus. 

F02TAL   CIRCULATION. 

The  pure  blood  is  brought  from  the  placenta  by  the  umbilical 
vein.  The  umbilical  vein  passes  through  the  umbilicus,  and 


520 


THE   DISSECTOR. 


enters  the  liver,  where  it  divides  into  several  branches,  which 
may  be  arranged  under  three  heads :  1st,  two  or  three,  which 
are  distributed  to  the  left  lobe.  2dly,  a  single  branch,  which 
communicates  with  the  portal  vein  in  the  transverse  fissure,  and 
supplies  the  right  lobe.  3dly,  a  large  branch,  the  ductus  veno- 

THE  FCETAL  CIRCULATION. — 1. 
The  umbilical  cord,  consisting  of 
the  umbilical  vein  and  two  umbili- 
cal arteries  ;  proceeding  from  the 
placenta  (2).  3.  The  umbilical 
vein  dividing  into  thre.e  branches  ; 
two  (4,  4),  to  be  distributed  to  the 
liver  ;  and  one  (5),  the  ductus  ve- 
nosus,  which  enters  the  inferior 
vena  cava  (6) .  7.  The  portal  vein, 
returning  the  blood  from  the  intes- 
tines, and  uniting  with  the  right 
hepatic  branch.  8.  The  right  au- 
ricle ;  the  course  of  the  blood  is 
denoted  by  the  arrow,  proceeding 
from  8,  to  9,  the  left  auricle.  10. 
The  left  ventricle ;  the  blood  fol- 
lowing the  arrow  to  the  arch  of  the 
aorta  (11) ,  to  be  distributed  through 
the  branches  given  off  by  the  arch 
to  the  head  and  upper  extremities. 
The  arrows  12  and  13,  represent 
the  return  of  the  blood  from  the 
head  and  upper  extremities  through 
the  jugular  and  subclavian  veins, 
to  the  superior  vena  cava  (14),  to 
the  right  auricle  (8),  and  in  the 
course  of  the  arrow  through  the 
right  ventricle  (15) ,  to  the  pulmo- 
nary artery  (16).  17.  The  ductus 
arteriosus,  which  appears  to  be  a 
proper  continuation  of  the  pulmo- 
nary artery ;  the  offsets  at  each 
side  are  the  right  and  left  pulmo- 
nary artery  cut  off;  these  are  of 
extremely  small  size  as  compared 
with  the  ductus  arteriosus.  The 
ductus  arteriosus  joins  the  descend- 
ing aorta  (18,  18),  which  divides 
into  the  common  iliacs,  and  these 
into  the  internal  iliacs,  which  be- 
come the  hypogastric  arteries  (19), 
and  return  the  blood  along  the 

umbilical  cord  to  the  placenta;  while  the  other  divisions,  the  external  iliacs 
(20),  are  continued  into  the  lower  extremities.  The  arrows  at  the  terminations 
of  these  vessels  mark  the  return  of  the  venous  blood  by  the  veins  to  the  infe- 
rior cava. 

sus,  which  passes  directly  backwards,  and  joins  the  inferior  cava. 
In  the  inferior  cava  the  pure  blood  becomes  mixed  with  that 
which  is  returning  from  the  lower  extremities  and  abdominal 


\J\J 


FCETAL   CIRCULATION.  '521 

viscera,  and  is  carried  through  the  right  auricle  (guided  by  the 
Eustachian  valve),  and  through  the  foramen  ovale,  into  the  left 
auricle.  From  the  left  auricle  it  passes  into  the  left  ventricle, 
and  from  the  left  ventricle  into  the  aorta,  whence  it  is  distri- 
buted, by  means  of  the  carotid  and  subclavian  arteries,  princi- 
pally to  the  head  and  upper  extremities.  From  the  head  and 
upper  extremities,  the  impure  blood  is  returned  by  the  superior 
vena  cava  to  the  right  auricle;  from  the  right  auricle  it  is  pro- 
pelled into  the  right  ventricle,  and  from  the  right  ventricle  into 
the  pulmonary  artery.  In  the  adult  the  blood  would  now  be 
circulated  through  the  lungs,  and  oxygenated  ;  but  in  the  foetus 
the  lungs  are  solid,  and  almost  impervious.  Only  a  small  quan- 
tity of  the  blood  passes  therefore  into  the  lungsj  the  greater 
part  rushes  through  the  ductus  arteriosus  into  the  commencement 
of  the  descending  aorta,  where  it  becomes  mingled  with  that  por- 
tion of  the  pure  blood  which  is  not  sent  through  the  carotid  and 
subclavian  arteries. 

Passing  along  the  aorta,  a  small  quantity  of  this  mixed  blood 
is  distributed  by  the  external  iliac  arteries  to  the  lower  extremi- 
ties; the  greater  portion  is  conveyed  by  the  internal  iliac,  hypo- 
gastric,  and  umbilical  arteries  to  the  placenta;  the  hypogastric 
arteries  proceeding  from  the  internal  iliacs,  and  passing  by  the 
side  of  the  fundus  of  the  bladder,  and  upwards  along  the  ante- 
rior wall  of  the  abdomen  to  the  umbilicus,  where  they  become 
the  umbilical  arteries. 

From  a  careful  consideration  of  this  circulation,  we  per- 
ceive : — 

1st.  That  the  pure  blood  from  the  placenta  is  distributed  in 
considerable  quantity  to  the  liver,  before  entering  the  general 
circulation.  Hence  arises  the  abundant  nutrition  of  that  organ, 
and  its  enormous  size  in  comparison  with  other  viscera. 

2dly.  That  the  right  auricle  is  the  scene  of  meeting  of  a  dou- 
ble current ;  the  one  coming  from  the  inferior  cava,  the  other 
from  the  superior,  and  that  they  must  cross  each  other  in  their 
respective  courses.  How  this  crossing  is  effected  the  theorist 
will  wonder ;  not  so  the  practical  anatomist ;  for  a  cursory  ex- 
amination of  the  fcetal  heart  will  show — 1.  That  the  direction  of 
entrance  of  the  two  vessels  is  so  opposite,  that  they  may  dis- 
charge their  currents  through  the  same  cavity  without  admixture. 
2.  That  the  inferior  cava  opens  almost  directly  into  the  left  au- 
ricle. 3.  That  by  the  aid  of  the  Eustachian  valve,  the  current 
in  the  inferior  cava  will  be  almost  entirely  excluded  from  the 
right  ventricle. 

3dly.  That  the  blood  which  circulates  through  the  arch  of  the 
aorta,  comes  directly  from  the  placenta;  and,  although  mixed 
with  the  impure  blood  of  the  inferior  cava,  yet  is  propelled  in  so 

44* 


522  THE   DISSECTOR. 

great  abundance  to  the  head  and  upper  extremities,  as  to  pro- 
vide for  the  increased  nutrition  of  those  important  parts,  and 
prepare  them,  by  their  greater  size  and  development,  for  the 
functions  which  they  are  required  to  perform  at  the  instant  of 
birth. 

4thly.  That  the  blood  circulating  in  the  descending  aorta  is 
very  impure,  being  obtained  principally  from  the  returning  cur- 
rent in  the  superior  cava ;  a  small  quantity  only  being  derived 
from  the  left  ventricle.  Yet  it  is  from  this  impure  blood  that 
the  nutrition  of  the  lower  extremities  is  provided.  Hence  we 
are  not  surprised  at  their  insignificant  development  at  birth  ; 
while  we  admire  the  providence  of  nature,  which  directs  the  nu- 
trient current  in  abundance,  to  the  organs  of  sense,  prehension, 
and  deglutition,  organs  so  necessary,  even  at  the  instant  of  birth, 
to  the  safety  and  welfare  of  the  creature. 

After  birth,  the  foramen  ovale  becomes  gradually  closed  by  a 
membranous  layer,  which  is  developed  from  the  margin  of  the 
opening  from  below  upwards,  and  completely  separates  the  two 
auricles.  The  situation  of  the  foramen  is  seen  in  the  adult 
heart,  upon  the  septum  auricularum,  and  is  called  the  fossa 
ovalis ;  the  prominent  margin  of  the  opening  is  the  annulus 


As  soon  as  the  lungs  have  become  inflated  by  the  first  act  of 
inspiration,  the  blood  of  the  pulmonary  artery  rushes  through 
its  right  and  left  branches  into  the  lungs,  to  be  returned  to  the 
left  auricle  by  the  pulmonary  veins.  Thus  the  pulmonary  circu- 
lation is  established.  Then  the  ductus  arteriosus  contracts  and 
degenerates  into  an  impervious  fibrous  cord,  serving  in  after  life 
simply  as  a  bond  of  union  between  the  left  pulmonary  artery  and 
the  concavity  of  the  arch  of  the  aorta. 

The  current  through  the  umbilical  cord  being  arrested,  the 
hypogastric  arteries  likewise  contract  and  become  impervious. 
The  umbilical  vein  and  ductus  venosus,  also  deprived  of  their  cir- 
culating current,  become  reduced  to  fibrous  cords,  the  former 
being  the  round  ligament  of  the  liver,  and  the  latter  a  fibrous 
band  which  may  be  traced  along  the  fissure  for  the  ductus  veno- 
sus to  the  inferior  vena  cava. 

NERVOUS  SYSTEM. — The  brain  is  very  soft,  almost  pulpy,  and 
has  a  reddish  tint  throughout ;  its  weight  at  birth,  relatively  to 
the  entire  body,  is  as  one  to  six,  and  the  difference  between  the 
white  and  gray  substance  is  imperfectly  marked.  The  nerves 
are  firm  and  well  developed. 

FOZTAL  ORGANS  OF  SENSE. 

Eye. — The  eyeballs  are  of  large  size  and  well  developed  at 
birth.  The  pupil  is  closed  by  a  vascular  membrane,  called  the 


FCETAL   THYMUS   GLAND.  523 

memlrana  pupillaris,  which  disappears  at  about  the  seventh 
month.  Sometimes  it  remains  permanently,  and  produces  blind- 
ness. It  consists  of  two  thin  membranous  layers,  between  which 
the  ciliary  arteries  are  prolonged  from  the  edge  of  the  itis,  and 
form  arches  and  loops  by  returning  to  it  again,  without  an- 
astomosing with  those  of  the  opposite  side. 

The  removal  of  the  membrane  takes  place  by  the  contraction 
of  these^  arches  and  loops,  towards  the  edge  of  the  pupil.  The 
capsule  of  the  lens  is  extremely  vascular. 

Ear — The  ear  is  remarkable  for  its  early  development ;  the 
labyrinth  and  ossicula  auditiis  are  ossified  at  an  early  period,  and 
the  latter  are  completely  formed  before  birth.  The  only  parts 
remaining  incomplete  are  the  mastoid  cells,  and  the  meatus  audi- 
torius.  The  membrana  tympani  in  the  f«tal  head  is  very  oblique, 
occupying  almost  the  basilar  surface  of  the  skull ;  hence  proba- 
bly arises  a  deficient  acuteness  in  the  perception  of  sound.  It  is 
also  extremely  vascular. 

Nose. — The  sense  of  smell  is  imperfect  in  the  infant,  as  may 
be  inferred  from  the  small  capacity  of  the  nasal  fossa?,  and  the 
non-development  of  the  ethmoid,  sphenoid,  frontal,  and  maxil- 
lary sinuses. 

FCETAL  THYROID  GLAND. 

The  thyroid  gland  is  of  large  size  in  the  foetus,  and  is  developed 
by  two  lateral  halves,  which  approach  and  become  connected  at 
the  middle  line,  so  as  to  constitute  a  single  gland.  It  is  doubt- 
ful whether  it  performs  any  special  function  in  foetal  life. 

FCETAL  THYMUS  GLAND. 

The  thymus  gland1  consists  "  of  a  thoracic  and  a  cervical  por- 
tion on  each  side.  The  former  is  situated  in  the  anterior  medi- 
astinum, and  the  latter  is  placed  in  the  neck  just  above  the  first 
bone  of  the  sternum,  and  behind  the  sterno-hyoidei  and  sterno- 
thyroidei  muscle."  It  extends  upwards  from  the  fourth  rib  as 
hi<rh  as  the  thyroid  gland,  resting  against  the  pericardium,  and 
separated  from  the  arch  of  the  aorta  and  great  vessels  by  the 
thoracic  fascia  in  the  chest,  and  lying  on  each  side  of  the  tra- 
chea in  the  neck. 

Although  described  usually  as  a  single  gland,  it  consists 
actually  of  two  lateral,  almost  symmetrical  glands,  connected 
with  each  other  by  cellular  tisue  only,  and  having  no  structural 

1  In  the  description  of  this  gland  I  have  adhered  closely  to  the  his- 
tory of  it,  given  by  Sir  Astley  Cooper,  in  his  monograph  "  On  the  Anatomy 
of  the  Thymus  ttland."  1832. 


524  THE   DISSECTOR. 

communication  ;  they  may  therefore  be  "  properly  called,  a  right 
and  left  thymus  gland." 

Between  the  second  and  third  months  of  embryonic  existence, 
the  thymus  is  so  small  as  to  be  only  "just  perceptible  ;"  and  con- 
tinues gradually  increasing  with  the  growth  of  the  foetus  until 
the  seventh.  At  the  eighth  month,  it  is  large;  but,  during  the 
ninth,  it  undergoes  a  sudden  change,  assumes  a  greatly  increased 
size,  and  at  birth  weighs  240  grains.  After  birth,  it  continues 
to  enlarge  until  the  expiration  of  the  first  year,  when  it  ceases  to 
grow,  and  gradually  diminishes,  until  at  puberty  it  has  almost 
disappeared. 

The  thymus  is  a  conglomerate  gland,  being  composed  of 
lobules  disposed  in  a  spiral  form  around  a  central  cavity.  The 
lobules  are  held  together  by  a  firm  cellular  tissue  ("reticulated"), 
and  the  entire  gland  is  inclosed  in  a  coarse  cellulo-fibrous  cap- 
sule 

The  lobules  are  very  numerous,  and  vary  in  size  from  that  of 
the  head  of  a  pin  to  a  moderate-sized  pea.  Each  lobule  con- 
tains in  its  interior  a  small  cavity,  or  "secretory  cell,"  and  seve- 
ral of  these  cells  open  into  a  small  "pouch'1'1  which  is  situated  at 
their  base,  and  leads  to  the  central  cavity,  the  "  reservoir  of  the 
thymus." 

The  reservoir  is  lined  in  its  interior  by  a  vascular  mucous 
membrane,  which  is  raised  into  ridges  by  a  layer  of  ligamentous 
bands  situated  beneath  it.  The  ligamentous  bands  proceed  in 
various  directions,  and  encircle  the  open  mouths  (pores)  of  the 
secretory  cells  and  pouches.  This  ligamentous  layer  serves  to 
keep  the  lobules  together,  and  prevent  the  injurious  distension  of 
the  cavity. 

When  either  gland  is  carefully  unravelled  by  removing  the 
cellulo-fibrous  capsule  and  vessels,  and  dissecting  away  the  reti- 
culated cellular  tissue  which  retains  the  lobules  in  contact,  the 
reservoir,  from  being  folded  in  a.  serpentine  manner  upon  itself, 
admits  of  being  drawn  out  into  a  lengthened  tubular  core?,1  around 
which  the  lobules  are  clustered  in  a  spiral  manner,  and  resemble 
knots  upon  a  cord,  or  a  string  of  beads. 

The  reservoir,  pouches,  and  cells,  contain  a  white  fluid  "  like 
chyle,"  or  "like  cream,  but  with  a  small  admixture  of  red  glo- 
bules." 

In  an  examination  of  the  thymic  fluid  which  I  lately  (1840) 
made,  with  a  Powell  microscope  magnifying  600  times  linear 
measure,  I  observed  that  the  corpuscles  were  very  numerous, 
smaller  than  the  blood  particles,  globular  and  oval  in  form, 

v  '  See  plates  in  Sir  Astley  Cooper's  work. 


F(ETAL  THYMUS  GLAND.  525 

irregular  in  outline,  variable  in  size,  and  provided  with  a  small 
central  nucleus. 

In  the  human  foetus,  this  fluid  has  been  found  by  Sir  Astley 
Cooper  iu  too  small  proportion  to  be  submitted  to  chemical 
analysis.  But  the  thymic  fluid  of  the  foetal  calf,  which  exists  in 
great  abundance,  gave  the  following  analytical  results  :'  100  parts 
of  the  fluid  contained  sixteen  parts  of  solid  matter,  which  con- 
sisted of — 

Incipient  fibrine, 

Albumen, 

Mucus,  and  muco-extractive  matter, 

Muriate  and  phosphate  of  potass, 

Phosphate  of  soda, 

Phosphoric  acid,  a  trace. 

According  to  the  researches  of  Simon9  and  Oesterlen,  the 
thymus  is  composed  of  polygonal  and  mutually  flattened  mem- 
branous cells,  measuring  from  half  a  line  to  two  lines  in  diameter, 
and  arranged  in  conical  masses  around  a  central  cavity.  Each 
cell  is  surrounded  by  a  capillary  plexus,  and  connected  to  neigh- 
boring cells  by  cellular  tissue  intermingled  with  elastic  fibres. 
The  corpuscles  found  in  the  fluid  of  the  thymus  are  dotted  nuclei 
measuring  ^¥L^  of  an  inch  in  diameter ;  and  are  subject  to  con- 
version into  nucleated  cells  and  fat-cells. 

The  arteries  of  the  thymus  gland  are  derived  from  the  internal 
mammary,  superior  and  inferior  thyroid. 

The  veins  terminate  in  the  left  vena  innominata,  and  some 
small  branches  in  the  thyroid  veins. 

The  nerves  are  minute,  and  derived  chiefly,  through  the  inter- 
nal mammary  plexus,  from  the  superior  thoracic  ganglion  of  the 
sympathetic.  Sir  Astley  Cooper  has  also  seen  a  branch  from 
the  junction  of  the  pneumogastric  and  sympathetic  pass  to  the 
side  of  the  gland. 

The  lymphatics  terminate  in  the  general  union  of  the  lymphatic 
vessels,  at  the  junction  of  the  internal  jugular  and  subclavian 
veins.  Sir  Astley  Cooper  has  injected  them  only  once  in  the 
human  foetus  ;  but  in  the  calf  he  finds  two  large  lymphatic  ducts, 
which  commence  in  the  upper  extremities  of  the  glands,  and  pass 
downwards,  to  terminate  at  the  junction  of  the  jugular  and  sub- 
clavian vein  at  each  side.  These  vessels  he  considers  to  be  the 
"  absorbent  ducts  of  the  glands  ;  '  thymic  ducts;1  they  are  the 
carriers  of  the  fluid  from  the  thymus  into  the  veins." 

Sir  Astley  Cooper  concludes  his  anatomical  description  of 
this  gland  with  the  following  observations  : — 

1  This  analysis  was  conducted  by  Dr.  Dowler,  of  Richmond. 
*  "A  Physiological  Essay  on  the  Thymus  Gland,"  4to.     1845. 
I 


526  THE   DISSECTOR. 

"As  the  thymus  secretes  all  the  parts  of  the  blood,  viz:  albu- 
men, fibrine,  and  particles,  is  it  not  probable  that  the  gland  is 
designed  to  prepare  a  fluid  well  fitted  for  the  foetal  growth  and 
nourishment  from  the  blood  of  the  mother  before  the  birth  of 
the  foetus,  and,  consequently,  before  chyle  is  formed  from  food  ? 
— and  this  process  continues  for  a  short  time  after  birth,  the 
quantity  of  fluid  secreted  from  the  thymus  gradually  declining 
as  that  of  chylification  becomes  perfectly  established." 

\  FCETAL  LUNGS. 

The  lungs,  previously  to  the  act  of  inspiration,  are  dense  and 
solid  in  structure,  and  of  a  deep  red  color.  Their  specific  gra- 
vity is  greater  than  water,  in  which  they  sink  to  the  bottom  ; 
whereas  lung  which  has  respired  will  float  upon  that  fluid.  The 
specific  gravity  is,  however,  no  test  of  the  real  weight  of  the 
lung,  the  respired  lung  being  actually  heavier  than  the  foetal. 
Thus  the  weight  of  the  foetal  lung,  at  about  the  middle  period 
of  uterine  life,  is  to  the  weight  of  the  body  as  1  to  60. *  But, 
after  respiration,  the  relative  weight  of  the  lung  to  the  entire 
body  is  as  1  to  30. 

FCETAL   HEART. 

The  heart  of  the  foetus  is  large  in  proportion  to  the  size  of  the 
body;  it  is  also  developed  very  early,  representing  at  first  a 
simple  vessel,  and  undergoing  various  degrees  of  complication 
until  it  arrives  at  the  compound  character  which  it  presents  after 
birth.  The  two  ventricles  form,  at  one  period,  a  single  cavity, 
which  is  afterwards  divided  into  two  by  the  septum  ventricu- 
lorum.  The  two  auricles  communicate  up  to  the  moment  of 
birth,  the  septum  being  incomplete,  and  leaving  a  large  opening 
between  them,  the  foramen  ovale  (foramen  of  Botal).2 

The  ductus  arteriosus  is  another  peculiarity  of  the  foetus,  con- 
nected with  the  heart ;  it  is  a  communication  between  the  left 
pulmonary  artery  and  the  aorta.  It  degenerates  into  a  fibrous 
cord  after  birth,  from  the  double  cause  of  a  diversion  in  the  cur- 
rent of  the  blood  towards  the  lungs,  and  from  the  pressure  of 
the  left  bronchus,  caused  by  its  distension  with  air. 

VISCERA  OF  THE  ABDOMEN. 

At  an  early  period  of  uterine  life,  and  sometimes  at  the  period 
of  birth,  as  I  have  twice  observed  in  the  imperfectly  developed 

1  Cruveilhier,  Anatomie  Descriptive,  vol.  ii.  p.  621. 

2  Leonard  Botal,  of  Piedmont,  was  the  first  of  the  moderns  who  gave 
an  account  of  this  opening,  in  a  work  published  in  1565.     His  descrip- 
tion is  very  imperfect.     The  foramen  was  well  known  to  Galen. 


FOZTAL   LIVER  AND   KIDNEYS.  527 

foetus,  two  minute  fibrous  threads  may  be  seen  passing  from  the 
umbilicus  to  the  mesentery.  These  are  the  remains  of  the  om- 
phalo-mesenteric  vessels. 

The  omphalo-mesenteric  are  the  first  developed  vessels  of  the 
germ:  they  ramify  upon  the  vesicula  umbilicalis,  or  yelk-bag, 
and  supply  the  newly  formed  alimentary  canal  of  the  embryo. 
From  them,  as  from  a  centre,  the  general  circulating  system  is 
produced.  After  the  establishment  of  the  placental  circulation 
they  cease  to  carry  blood,  and  dwindle  to  the  size  of  mere  threads, 
which  may  be  easily  demonstrated  in  the  early  periods  of  uterine 
life;  but  are  completely  removed,  excepting  under  peculiar  cir- 
cumstances, at  a  later  period. 

The  stomach  is  of  small  size,  and  the  great  extremity  but  little 
developed.  It  is  also  more  vertical  in  direction  the  earlier  it  is 
examined,  a  position  that  would  seem  due  to  the  enormous  mag- 
nitude of  the  liver,  and  particularly  of  its  left  lobe. 

The  appendix  vermiformis  COKCI  is  long  and  of  large  size,  and 
is  continued  directly  from  the  central  part  of  the  cul-de-sac  of 
the  caecum,  of  which  it  appears  to  be  a  constricted  continuation. 
This  is  the  character  of  the  appendix  caeci  in  the  higher  quadru- 
mana. 

The  large  intestines  are  filled  with  a  dark  green  viscous  secre- 
tion, called  meconium  (p^xuv,  poppy),  from  its  resemblance  to  the 
inspissated  juice  of  the  poppy. 

The  pancreas  is  comparatively  larger  in  the  foetus  than  in  the 
adult. 

The  spleen  is  comparatively  smaller  in  the  foetus  than  in  the 
adult. 

FCETAL  LIVER. 

The  liver  is  the  first  formed  organ  in  the  embryo.  It  'is 
developed  from  the  alimentary  canal,  and  at  about  the  third 
week  fills  the  whole  abdomen,  and  is  one-half  the  weight  of  the 
entire  embryo.  At  the  fourth  month,  the  liver  is  of  immense 
si/.c,  in  proportion  to  the  bulk  of  the  foetus.  At  birth,  it  is  of  very 
large  size,  and  occupies  the  whole  upper  part  of  the  abdomen. 
Tlic  left  lobe  is  as  large  as  .the  right,  and  the  falciform  ligament 
corresponds  with  the  middle  line  of  the  body.  The  liver  dimi- 
nishes rapidly  after  birth,  probably  from  obliteration  of  the  um- 
bilical vein. 

KIDNEYS  AND  SUPRA-RENAL  CAPSULES. 

The  kidneys  present  a  lobulated  appearance  in  the  foetus, 
which  is  their  permanent  type  among  some  animals,  as  the  bear, 
the  otter,  and  cetacea. 

The  supra-renal  capsules  are  organs  which  appear,  from  their 


528  THE   DISSECTOR. 

early  and  considerable  development,  to  belong  especially  to  the 
economy  of  the  foetus.  They  are  distinctly  formed  at  the  second 
month  of  embryonic  life,  and  are  greater  in  size  and  weight  than 
the  kidneys.  At  the  third  or  fourth  month,  they  are  equalled  in 
bulk  by  the  kidneys ;  and  at  birth,  they  are  about  one-third  less 
than  those  organs. 

VISCERA  OF  THE  PELVIS. 

The  bladder  in  the  foetus  is  long  and  conical,  and  situated 
altogether  above  the  upper  border  of  the  ossa  pubis,  which  are  as 
yet  small  and  undeveloped.  It  is,  indeed,  an  abdominal  viscus, 
and  is  connected  superiorly  with  a  fibrous  cord,  called  the  ura- 
chus,  of  which  it  appears  to  be  an  expansion. 

The  urachus  is  continued  upwards  to  the  umbilicus,  and  be- 
comes connected  with  the  umbilical  cord.  In  animals  it  is  a 
pervious  duct,  and  is  continuous  with  one  of  the  membranes  of 
the  embryo,  the  allantois.  It  has  been  found  pervious  in  the 
human  foetus,  and  the  urine  has  been  known  to  pass  through  the 
umbilicus.  Calculous  concretions  have  also  been  found  in  its 
course. 

The  uterus,  in  the  early  periods  of  embryonic  existence,  ap- 
pears bifid,  from  the  large  size  of  the  Fallopian  tubes,  and  the 
small  development  of  the  body  of  the  organ.  At  the  end  of  the 
fourth  month,  the  body  assumes  a  larger  bulk,  and  the  bifid  ap- 
pearance is  lost.  The  cervix  uteri  in  the  foetus  is  larger  than  the 
body  of  the  organ. 

The  ovaries  are  situated,  like  the  testicles,  in  the  lumbar 
region,  near  the  kidneys,  and  descend  from  thence,  gradually, 
into  the  pelvis. 

FCETAL  TESTES. 

The  testicles  in  the  embryo  are  situated  in  the  lumbar  regions, 
immediately  in  front  of,  and  somewhat  below  the  kidneys. 
They  have  connected  with  them  inferiorly,  a  peculiar  structure, 
which  assists  in  their  descent,  and  is  called  the  gubernaculuni 
testis. 

•The  gubernaculum  is  a  soft  conical  -cord,  composed  of  cellular 
tissue,  containing  in  its  areolae  a  gelatiniform  fluid.  In  the  ab- 
domen, it  lies  in  front  of  the  psoas  muscle,  and  passes  along  the 
spermatic  canal,  which  it  serves  to  distend  for  the  passage  of  the 
testis.  It  is  attached,  by  its  superior  and  larger  extremity,  to 
the  lower  end  of  the  testis  and  epididymis ;  and  by  the  inferior 
extremity,  to  the  bottom  of  the  scrotum.  The  gubernaculum  is 
surrounded  by  a  thin  layer  of  muscular  fibres — the  cremaster, 
which  pass  upwards  upon  this  body,  to  be  attached  to  the  testis. 


FCETAL  TESTES.  529 

Inferiorly,  the  muscular  fibres  divide  into  three  processes,  which, 
according  to  Mr.  Curling,1  are  thus  attached  :  "  The  external 
and  broadest  is  connected  to  Poupart's  ligament  in  the  inguinal 
canal ;  the  middle  forms  a  lengthened  band,  which  escapes  at  the 
external  abdominal  ring,  and  descends  to  the  bottom  of  the 
scrotum,  where  it  joins  the  dartos  ;  the  internal  passes  in  the  di- 
rection inwards,  and  has  a  firm  attachment  to  the  os  pubis  and 
sheath  of  the  rectus  muscle.  Besides  these,  a  number  of  muscu- 
lar fibres  are  reflected  from  the  internal  oblique  on  the  front  of 
the  gubernaculum." 

The  descent  of  the  testicle  is  gradual  and  progressive.  Between 
the  fifth  and  sixth  month  it  has  reached  the  lower  part  of  the 
psoas  muscle  ;  and  during  the  seventh,  it  makes  its  way  through 
the  spermatic  canal,  and  descends  into  the  scrotum. 

While  situated  in  the  lumbar  region,  the  testis  and  guberna- 
culum  are  placed  behind  the  peritoneum,  by  which  they  are  invest- 
ed upon  their  anterior  surface  and  sides.  As  they  descend,  the 
investing  peritoneum  is  carried  downwards  with  the  testes  into 
the  scrotum,  forming  a  lengthened  pouch,  which  by  its  upper  ex- 
tremity opens  into  the  cavity  of  the  peritoneum.  The  upper 
part  of  this  pouch,  being  compressed  by  the  spermatic  canal,  is 
gradually  obliterated,  the  .  obliteration  extending  downwards 
along  the  spermatic  cord  nearly  to  the  testis.  That  portion  of 
the  peritoneum  which  immediately  surrounds  the  testis  is,  by  the 
above  process,  cut  off  from  its  continuity  with  the  peritoneum, 
and  is  termed  the  tunica  vaginalis ;  and  as  this  membrane  must 
be  obviously  a  shut  sac,  one  portion  of  it  investing  the  testis, 
and  the  other  being  reflected  so  as  to  form  a  loose  bag  around  it, 
its  two  portions  have  received  the  appellations  of  tunica  vaginalis 
propria,  and  tunica  vaginalis  reflexa. 

The  descent  of  the  testes  is  effected  by  means  of  the  traction 
of  the  muscle  of  the  gubernaculum — the  cremaster.  "  The 
fibres,"  writes  Mr.  Curling,  "  proceeding  from  Poupart's  liga- 
ment, and  the  obliquus  mternus,  tend  to  guide  the  gland  into  the 
inguinal  canal:  those  attached  to  the  os  pubis  to  draw  it  below 
the  abdominal  ring;  and  the  process  descending  to  the  scrotum, 
to  direct  it  to  its  final  destination."  During  the  descent,  "the 
muscle  of  the  testis  is  gradually  everted,  until,  when  the  transi- 
tion is  completed,  it  forms  a  muscular  envelop  external  to  the 
process  of  peritoneum,  which  surrounds  the  gland  and  the  front 
of  the  cord.  The  mass  composing  the  central  part  of  the  guber- 
naculum,  which  is  so  soft,  lax,  and  yielding,  as  in  every  way  to 
facilitate  these  changes,  becomes  gradually  diffused,  and,  after  the 

1  "  On  the  structure  of  the  Gubernaculum,"  &c.,by  Mr.  Curling,  of  the 
London  Hospital.     Lancet,  vol.  ii.  1840-41,  p.  70. 
45 


530  THE   DISSECTOR. 

arrival  of  the  testicle  in  the  scrotum,  contributes  to  form  the 
loose  cellular  tissue  which  afterwards  exists  so  abundantly  in  this 
part."  The  attachment  of  the  gubernaculum  to  the  bottom  of 
the  scrotum,  is  indicated  throughout  life  by  distinct  traces. 


CHAPTER.    XIII. 

OP  THE  LIGAMENTS. 

THE  bones  are  variously  connected  with  each  other  in  the  con- 
struction of  the  skeleton,  and  the  connection  between  any  two 
bones  constitutes  a  joint  or  articulation.  If  the  joint  be  immova- 
ble, the  surfaces  of  the  bones  are  applied  in  direct  contact ;  hut 
if  motion  be  intended,  the  opposing  surfaces  are  expanded  and 
coated  by  an  elastic  substance  named  cartilage  ;  a  fluid  secreted 
by  a  membrane  closed  on  all  sides  lubricates  their  surface,  and 
they  are  firmly  held  together  by  means  of  short  bands  of  glisten- 
ing fibres,  which  are  called  ligaments  (ligare,  to  bind).  The 
study  of  the  ligaments  is  termed  syndesmology  (avv,  together, 
Si-epos,  bound),  which,  with  the  anatomy  of  the  articulations, 
forms  the  subject  of  the  present  chapter. 

The  forms  of  articulation  met  with  in  the  human  frame  may 
be  considered  under  three  classes  :  Synarthrosis,  Amphi-arthro- 
sis,  and  Diarthrosis. 

SYNARTHROSIS  (ovv,  ap0p«rftj,  articulation)  is  expressive  of  the 
fixed  form  of  joint,  in  which  the  bones  are  immovably  connected 
with  each  other.  The  kinds  of  synarthrosis  are  four  in  number 
— Sutura,  Harmonia,  Schindylesis,  Gomphosis.  In  the  con- 
struction of  sutures,  the  substance  of  the  bones  is  not  in  imme- 
diate contact ;  but  is  separated  by  a  layer  of  membrane,  which 
is  continuous,  externally,  with  the  pericranium,  and,  internally, 
with  the  dura  mater.  It  is  the  latter  connection  which  gives  rise 
to  the  great  difficulty  sometimes  experienced  in  tearing  the  cal- 
varium  from  the  dura  mater.  Cruveilhier  describes  this  inter- 
posed membrane  as  the  sutural  cartilage  ;  I  never  saw  any  struc- 
ture in  the  sutures  which  could  be  regarded  as  cartilage,  and  the 
history  of  the  formation  of  the  cranial  bones  would  suggest  a 
different  explanation.  Gomphosis  (yo/i^oj,  a  nail),  is  expressive 
of  the  insertion  of  one  bone  into  another,  in  the  same  manner 
that  a  nail  is  fixed  into  a  board  ;  this  is  illustrated  in  the  articu- 
lation of  the  teeth  with  the  alveoli  of  the  maxillary  bones. 

AMPHI-ARTHROSIS  (d^t,  both,  <i'p0p«<jis)  is  a  joint  intermediate 
in  aptitude  for  motion,  between  the  immovable  synarthrosis  and 


FORMS  OF  ARTICULATION.  531 

the  movable  diarthrosis.  It  is  constituted  by  the  approxima- 
tion of  surfaces  partly  coated  with  cartilage  lined  by  synovial 
membrane,  and  partly  connected  by  interosseous  ligaments,  or  by 
the  intervention  of  an  elastic  fibro-cartilage  which  adheres  to 
the  ends  of  both  bones.  Examples  of  this  mode  of  articulation 
are  seen  in  the  union  between  the  bodies  of  the  vertebrae,  of  the 
sacrum  with  the  coccyx,  of  the  pieces  of  the  sternum,  the  sacro- 
iliac  and  pubic  symphysis  (av^vnv,  to  grow  together),  and,  ac- 
cording to  some,  of  the  necks  of  the  ribs,  with  the  transverse 
processes. 

DIARTUROSIS  (5id,  through,  ap0pwrfi$)  is  the  movable  articula- 
tion, which  constitutes  by  far  the  greater  number  of  the  joints  of 
the  body.  The  degree  of  motion  in  this  class  has  given  rise  to  a 
subdivision  into  three  genera :  Arthrodia,  Ginglymus,  and  Enar- 
throsis. 

Arthrodia  is  the  movable  joint  in  which  the  extent  of  motion 
is  slight  and  limited,  as  in  the  articulations  of  the  clavicle,  of  the 
ribs,  articular  processes  of  the  vertebrae,  axis  with  the  atlas, 
radius  with  the  ulna,  fibula  with  the  tibia,  carpal  and  metacarpal, 
tarsal  and  metatarsal  bones. 

Ginglymus  (ycyyXv/*6$,  a  hinge),  or  hinge-joint,  is  the  move- 
ment of  the  bones  upon  each  other  in  two  directions  only,  viz : 
forwards  and  backwards  ;  but  the  degree  of  motion  may  be  very 
considerable.  The  instances  of  this  form  of  joint  are  numerous  ; 
they  comprehend  the  elbow,  wrist,  metacarpo-phalangeal  and 
phalangeal  joints  in  the  upper  extremity  ;  and  the  knee,  ankle, 
metatarso-phalangeal  and  phalangeal  joints  in  the  lower  ex- 
tremity. The  lower  jaw  may  also  be  admitted  into  this  category, 
as  partaking  more  of  the  character  of  the  hinge  joint  than  of  the 
less  movable  arthrodia. 

The  form  of  the  ginglymoid  joint  is  somewhat  quadrilateral, 
and  each  of  its  four  sides  is  provided  with  a  ligament,  which  is 
named  from  its  position,  anterior,  posterior,  internal,  or  external 
lateral.  The  lateral  ligaments  are  thick  and  strong,  and  the 
chief  bond  of  union  between  the  bones.  The  anterior  and  poste- 
rior are  thin  and  loose,  in  order  to  permit  the  required  extent  of 
movement. 

Knarthrosis  (tv,  in,  opflptxns)  is  the  most  extensive  in  its  range 
of  motion  of  all  the  movable  joints.  From  the  manner  of  con- 
nection and  form  of  the  bones  in  this  articulation,  it  is  called 
the  ball-and-socket  joint.  There  are  two  instances  in  the  body, 
viz  :  the  hip  and  the  shoulder. 

I  have  been  in  the  habit  of  adding  to  the  preceding  the  carpo- 
metacarpal  articulation  of  the  thumb,  although  not  strictly  a  ball- 
and-socket  joint,  from  the  great  extent  of  motion  which  it  enjoys 
and  from  the  nature  of  the  ligament  connecting  the  bones.  As 


532  THE   DISSECTOR. 

far  as  the  articular  surfaces  are  concerned,  it  is  rather  a  double 
than  a  single  ball-and-socket ;  and  the  whole  of  these  considera- 
tions remove  it  from  the  simple  arthrodial  and  ginglymoid  groups. 
The  ball-and-socket  joint  has  a  circular  form  ;  and,  in  place  of 
the  four  distinct  ligaments  of  4he  ginglymus,  is  inclosed  in  a  bag 
of  ligameiitous  membrane,  called  a  capsular  ligament. 

The  kinds  of  articulation  may  probably  be  conveyed  in  a  more 
satisfactory  manner  in  the  tabular  form,  thus  : — 

Examples. 

f  Sutura          -         -     bones  of  the  skull. 
T.«oia      J  Harmonia     -         -     superior  maxillary  bones. 
1   Schindylesis          -     vomer  with  rostrum. 
L  Gomphosis  -         -     teeth  with  alveoli. 

AmpM-arthrosis     ... 

(  Arthrodia     -         -     carpal  and  tarsal  bones. 
Diarthrosis.       •<  Ginglymus   -         -     elbow,  wrist,  knee,  ankle. 

(  Enarthrosis  -         -     hip,  shoulder. 

The  motions  permitted  in  joints  may  be  referred  to  four 
heads,  viz  :  Gliding,  Angular  movement,  Circumduction,  and 
Rotation. 

1.  Gliding  is  the  simple  movement  of  one  articular  surface 
upon  another,  and  exists,  to  a  greater  or  less  extent,  in  all  the 
joints.     In  the  least  movable  joints,  as  in  the  carpus  and  tarsus, 
this  is  the  only  motion  which  is  permitted. 

2.  Angular  movement  may  be  performed  in  four  different  di- 
rections :  either  forwards  and  backwards,  as  in  flexion  and  ex- 
tension ;  or  inwards  and  outwards,  constituting  adduction  and 
abduction.     Flexion  and  extension  are  illustrated  in  the  gingly- 
moid joint,  and  exist  in  a  large  proportion  of  the  joints  of  the 
body.     Adduction  and  abduction,  conjoined  with  flexion  and 
extension,  are  met  with  complete,   only  in  the  most  movable 
joints,  as  in  the  shoulder,  hip,  and  thumb.     In  the  wrist  and 
ankle,  adduction  and  abduction  are  only  partial. 

3.  Circumduction  is  most  strikingly  exhibited  in  the  shoulder 
and  hip-joints ;  it  consists  in  the  slight  degree  of  motion  which 
takes  place  between  the  head  of  a  bone  and  its  articular  cavity, 
while  the  extremity  of  the  limb  is  made  to  describe  a  large  circle 
upon  a  plane  surface.     It  is  also  seen,  but  in  a  less  degree,  in 
the  carpo-metacarpal  articulation  of  the  thumb,  metacarpo-pha- 
langeal  articulations  of  the  fingers  and  toes,  and  in  the  elbow 
when  that  joint  is  flexed  and  the  end  of  the  humerus  fixed. 

4.  Rotation  is  the  movement  of  a  bone  upon  its  own  axis,  and 
is  illustrated  in  the  hip  and  shoulder,  or  better,  in  the  rotation 
of  the  cup  of  the  radius  against  the  eminentia  capitata  of  the 


ARTICULATIONS   OP   THE   VERTEBRAE.  533 

humerus.  Rotation  is  also  observed  in  the  movements  of  the 
atlas  upon  the  axis,  in  which  the  odontoid  process  serves  as  a 
pivot,  around  which  the  atlas  turns. 

The  structures  entering  into  the  composition  of  a  joint  are 
bone,  cartilage,  fibrous  tissue,  adipose  tissue,  and  synovial  mem- 
brane. Cartilage  forms  a  thin  coating  to  the  articular  extremi- 
ties of  bones,  sometimes  presenting  a  smooth  surface  which 
moves  OH  a  corresponding  smooth  surface  of  the  articulating 
bone ;  sometimes  forming  a  plate  smooth  on  both  surfaces  and 
interposed  between  the  cartilaginous  ends  of  two  bones,  inter- 
articular  ;  and  sometimes  acting  as  the  connecting  medium  be- 
tween bones  without  any  free  surface,  interosseous.  Fibrous 
tissue  enters  into  the  construction  of  joints  under  the  form  of 
ligament,  in  one  situation  constituting  bands  of  various  breadth 
and  thickness;  in  another,  a  layer  which  extends  completely 
round  the  joint,  and  is  then  called  a  capsular  ligament.  All  the 
ligaments  of  joints  are  composed  of  that  variety  of  fibrous  tissue 
termed  white  fibrous  tissue ;  but  in  some  situations  ligaments  are 
found,  which  consist  of  yellow  fibrous  tissue;  for  example,  the 
ligamenta,  subflava  of  the  arches  of  the  vertebral  column.  Adi- 
pose tissue  exists  in  variable  quantity  in  relation  with  joints, 
where  it  performs,  among  other  offices,  that  of  a  valve  or  spring, 
which  occupies  any  vacant  space  that  may  be  formed  during  the 
movements  of  the  joint,  and  effectually  prevents  the  occurrence 
of  a  vacuum  in  those  cavities.  This  purpose  of  adipose  tissue  is 
exemplified  in  the  cushion  of  fat  at  the  bottom  of  the  acetabulum, 
and  in  the  similar  cushion  behind  the  ligamentum  patellae. 
Synovial  membrane  constitutes  the  smooth  and  polished  lining 
of  a  joint,  and  contains  the  fluid  termed  synovia,  by  means  of 
which  the  adapted  surfaces  are  enabled  to  move  upon  each  other 
with  perfect  ease  and  freedom. 

ARTICULATIONS. 

The  joints  may  be  arranged,  according  to  a  natural  division, 
into  those  of  the  trunk,  those  of  the  upper  extremity,  and  those 
of  the  lower  extremity. 

LIGAMENTS  OP  THE  TRUNK. — The  articulations  of  the  trunk 
are  divisible  into  ten  groups,  viz  : — 

1.  Of  the  vertebral  column. 

2.  Of  the  atlas,  with  the  occipital  bone. 

3.  Of  the  axis,  with  the  occipital  bone. 

4.  Of  the  atlas,  with  the  axis. 

5.  Of  the  lower  jaw. 

6.  Of  the  ribs,  with  the  vertebrae. 

7.  Of  the  ribs,  with  the  sternum,  and  with  each  other. 

45* 


534  THE   DISSECTOR. 

8.  Of  the  sternum. 

9.  Of  the  vertebral  column,  with  the  pelvis. 
10.  Of  the  pelvis. 

1.  Articulation  of  the  Vertebral  Column. — The  ligaments  con- 
necting together  the  different  pieces  of  the  vertebral  column,  ad- 
mit of  the  same  arrangement  as  that  of  the  vertebrae  themselves. 
Thus  the  ligaments — 

Of  the  bodies,  are  the —        Anterior  common  ligament, 

Posterior  common  ligament, 
Intervertebral  substance. 

Of  the  arches,  Ligamenta  subflava. 

Of  the  articular  processes,     Capsular  ligaments, 

Synovial  membranes. 

Of  the  spinous  processes,       Inter-spinous, 

Supra-spinous. 

Of  the  transverse  processes,  Inter-transverse. 
BODIES. — The  anterior  common  ligament  is  a  broad  and  ribbon- 
like  band  of  ligamentous  fibres,  extending  along  the  front  surface 
of  the  vertebral  column,  from  the  axis  to  the  sacrum.  It  is  inti- 
mately connected  with  the  intervertebral  substance  and  less  closely 
with  the  bodies  of  the  vertebra.  In  the  dorsal  region  it  is 
thicker  than  in  the  cervical  and  lumbar,  and  consists  of  a  median 
and  two  lateral  portions  separated  from  each  other  by  a  series  of 
openings  for  the  passage  of  vessels.  The  ligament  is  composed 
of  fibres  of  various  lengths,  closely  interwoven  with  each  other; 
the  deeper  and  shorter  crossing  the  intervertebral  substance  from 
one  vertebra  to  the  next,  and  the  superficial  and  longer  fibres 
crossing  three  or  four  vertebra. 

The  anterior  common  ligament  is  in  relation,  by  its  posterior 
or  vertebral  surface,  with  the  intervertebral  substance,  the  bodies 
of  the  vertebra,  and  with  the  vessels,  principally  veins,  which 
separate  its  central  from  its  lateral  portions.  By  its  anterior  or 
visceral  surface  it  is  in  relation,  in  the  neck,  with  the  longus  colli 
muscles,  the  pharynx,  and  the  oesophagus ;  in  the  thoracic  region, 
with  the  aorta,  venaa  azygos,  and  thoracic  duct;  and  in  the  lum- 
bar region,  with  the  aorta,  right  renal  artery,  right  lumbar  arte- 
ries, arteria  sacra  media,  vena  cava  inferior,  left  lumbar  veins, 
receptaculum  chyli,  commencement  of  the  thoracic  duct,  and  ten- 
dons of  the  lesser  muscle  of  the  diaphragm,  with  the  fibres  of 
which  the  ligamentous  fibres  interlace. 

The  posterior  common  ligament  lies  upon  the  posterior  surface 
of  the  bodies  of  the  vertebrae,  and  extends  from  the  axis  to  the 
sacrum.  It  is  broad  opposite  the  intervertebral  substance,  to 
whiclj  it  is  closely  adherent;  and  narrow  and  thick  over  the 


ARCHES.  535 

bodies  of  the  vertebra?,  from  which  it  is  separated  by  the  veins  of 
the  base  of  each  vertebra.  It  is  composed,  like  the  anterior 
ligament,  of  shorter  and  longer  fibres,  which  are  disposed  in  a 
similar  manner.  This  ligament  is  broader  above  than  below,  the 
reverse  of  the  anterior  common  ligament. 

The  posterior  common  ligament  is  in  relation,  by  its  anterior 
surface,  with  the  intervertebral  substance,  bodies  of  the  vertebrae, 
and  venae  basium  vertebrarum;  and  by  its  posterior  surface,  with 
the  dura  mater  of  the  spinal  cord,  some  loose  cellular  tissue  and 
numerous  small  veins  being  interposed. 

The  intervertebral  substance  is  a  lenticular  disk  of  fibrous  car- 
tilage, interposed  between  each  of  the  vertebras  from  the  axis  to 
the  sacrum,  and  retaining  them  firmly  in  connection  with  each 
other.  It  differs  in  thickness  in  different  parts  of  the  column, 
and  varies  in  depth  at  different  points  of  its  extent;  thus,  it  is 
thickest  in  the  lumbar  region,  deepest  in  front  in  the  cervical  and 
lumbar  regions,  and  behind  in  the  dorsal  region;  and  contributes 
to  the  formation  of  the  natural  curves  of  the  cervical  and  lumbar 
portions  of  the  vertebral  column.  The  aggregate  length  of  the 
intervertebral  substance  has  been  estimated  at  about  one-fourth 
of  that  of  the  vertebral  column,  excluding  the  sacrum  and  coccyx. 

When  the  intervertebral  substance  is  bisected  either  horizon- 
tally or  vertically,  it  is  seen  to  be  composed  of  a  series  of  layers 
of  dense  fibrous  tissue,  separated  by  interstices  filled  with  the 
softer  kind.  The  central  part  of  each  intervertebral  disk  is 
wholly  made  up  of  this  softer  fibrous  cartilage,  which  has  the  ap- 
pearance of  a  pulp,  and  is  so  elastic  as  to  rise  above  the  level  of 
the  section  as  soon  as  its  division  is  completed.  When  examined 
from  the  front,  the  layers  are  found  to  consist  of  fibres  passing 
obliquely  between  the  two  vertebrae ;  in  one  layer  passing  from 
left  to  right,  in  the  next  from  right  to  left,  alternating  in  each 
successive  layer. 

ARCHES. — The  ligamenta  subflava  are  two  thin  planes,  of  yel- 
low fibrous  tissue,  situated  between  the  arches  of  each  pair  of 
vertebrae,  from  the  axis  to  the  sacrum.  From  the  imbricated 
position  of  the  laminae  they  are  attached  to  the  posterior  surface 
of  the  vertebra  below,  and  to  the  anterior  surface  of  the  arch  of 
the  vertebra  above,  and  are  separated  from  each  other  at  the  mid- 
dle line  by  a  slight  interspace.  They  counteract,  by  their  elas- 
ticity, the  efforts  of  the  flexor  muscles  of  the  trunk ;  and  by  pre- 
serving the  upright  position  of  the  spine,  limit  the  expenditure  of 
muscular  force.  They  are  longer  in  the  cervical  than  in  the 
other  regions  of  the  spine,  and  are  thickest  in  the  lumbar  region. 

The  ligamenta  subflava  are  in  relation  by  both  surfaces  with 
the  meningo-rachidian  veins,  and  internally  they  are  separated 


536  THE   DISSECTOR. 

from  the  dura  matter  of  the  spinal  cord  by  those  veins  and  some 
loose  cellular  and  adipose  tissue. 

ARTICULAR  PROCESSES. — The  ligaments  of  the  articular  pro- 
cesses  of  the  vertebra  are  thin  layers  of  ligamentous  fibres  which 
surround  and  inclose  the  synovial  membranes  ;  the  latter  being 
looser  in  the  cervical  than  in  the  other  regions  of  the  spine. 

SPINOUS  PROCESSES. — The  inter-spinous  ligaments,  thin  and 
membranous,  are  extended  between  the  spinous  processes  in  the 
dorsal  and  lumbar  regions.  They  are  thickest  in  the  latter ;  and 
are  in  relation  with  the  multifidus  spinse  muscle,  at  each  side. 

The  supra-spinous  ligament  is  a  strong  fibrous  cord,  which 
extends  from  the  apex  of  the  spinous  process  of  the  last  cervi- 
cal vertebra  to  the  sacrum,  being  attached  to  each  spinous  pro- 
cess in  its  course  ;  like  the  anterior  and  posterior  common  liga- 
ments, it  is  composed  of  fibres  of  unequal  length,  the  deeper 
fibres  passing  from  one  vertebra  to  the  next,  the  superficial 
fibres  extending  over  several  spinous  processes  ;  it  is  thickest  in 
the  lumbar  region.  The  continuation  of  this  ligament  upwards 
to  the  tuberosity  of  the  occipital  bone,  constitutes  the  rudiment- 
ary ligamentum  nuchae  of  man.  The  latter  is  strengthened,  as 
in  animals,  by  a  thin  slip  from  the  spinous  process  of  each  cervi- 
cal vertebra. 

TRANSVERSE  PROCESSES. — The  inter-transverse  ligaments  are 
thin  and  membranous  ;  they  are  found  only  between  the  transverse 
processes  of  the  lower  dorsal  vertebrae. 

2.   Articulation  of  the  Atlas  with  the    Occipital  Bone. — The 
ligaments  of  this  articulation  are  seven  in  number — 
Two  anterior  occipito-atloid, 
Posterior  occipito-atloid, 
Lateral  occipito-atloid, 
Two  capsular. 

Of  the  two  anterior  ligaments,  one  is  a  rounded  cord,  situated 
in  the  middle  line,  and  superficially  to  the  other.  It  is  attached, 
above,  to  the  basilar  process  of  the  occipital  bone  ;  and,  below 
to  the  anterior  tubercle  of  the  atlas.  The  deeper  ligament  is  a 
broad  membranous  layer,  attached,  above,  to  the  margin  of  the 
occipital  foramen  between  the  two  condyles  ;  and,  below,  to  the 
whole  length  of  the  anterior  arch  of  the  atlas.  It  is  in  relation 
in  front,  with  the  recti  antici  minores ;  and,  behind,  with  the 
odontoid  ligaments. 

The  posterior  ligament  is  thin  and  membranous  :  it  is  attached, 
above,  to  the  margin  of  the  occipital  foramen  between  the  two 
condyles  ;  and,  below,  to  the  posterior  arch  of  the  atlas.  It  is 
closely  adherent  to  the  dura  mater  by  its  inner  surface  ;  and  forms 
a  ligamentous  arch  at  each  side,  for  the  passage  of  the  vertebral 


ARTICULATIONS   OF   THE   ATLAS.  537 

arteries  and  first  cervical  nerves.     It  is  in  relation,  posteriorly, 
with  the  recti  postici  rainores  and  obliqui  superiores. 

The  lateral  ligaments  are  strong  fasciculi  of  ligarnentous  fibres, 
attached,  below,  to  the  base  of  the  transverse  process  of  the 
atlas  at  each  side,  and,  above,  to  the  transverse  process  of  the 
occipital  bone.  With  a  ligaraentous  expansion  derived  from  the 
vaginal  process  of  the  temporal  bone,  these  ligaments  form  a 
strong  sheath  around  the  vessels  and  nerves  which  pass  through 
the  carotid  and  jugular  foramina. 

The  capsular  Ugaments  are  the  thin  and  loose  ligamentous 
capsules,  which  surround  the  synovial  membranes  of  the  articula- 
tions between  the  condyles  of  the  occipital  bone  and  the  superior 
articular  processes  of  the  atlas.  The  ligamentous  fibres  are  most 
numerous  upon  the  anterior  and  external  part  of  the  articulation. 

The  movements  taking  place  between  the  cranium  and  atlas,  are  those 
of  flexion  and  extension,  giving  rise  to  the  forward  nodding  of  the  head. 
When  this  motion  is  increased  to  any  extent,  the  whole  of  the  cervical 
region  concurs  in  its  production. 

Articulation  of  the  Axis  with  the  Occipital  Bone. — The  liga- 
ments of  this  articulation  are  three  in  number — 

Occipito-axoid,  Two  odontoid. 

The  occipito-axoid  ligament  (apparatus  ligamentosus  colli)  is  a 
broad  band,  which  covers  in  the  odontoid  process  and  its  liga- 
ments. It  is  attached,  below,  to  the  body  of  the  axis,  where  it 
is  continuous  with  the  posterior  common  ligament ;  superiorly, 
it  is  inserted  by  a  broad  expansion,  into  the  basilar  groove  of 
the  occipital  bone.  It  is  firmly  connected,  opposite  the  body  of 
the  axis,  with  the  dura  mater;  and  sometimes  is  described  as 
consisting  of  a  central  and  two  lateral  portions ;  this,  however, 
is  an  unnecessary  refinement. 

The  odontoid  ligaments  (alar)  are  two  short  and  thick  fasciculi 
of  fibres,  which  pass  outwards  from  the  apex  of  the  odontoid 
process,  to  the  sides  of  the  occipital  foramen  and  condyles.  A 
third  and  smaller  fasciculus  (ligamentum  suspensorium)  proceeds 
from  the  apex  of  the  odontoid  process  to  the  anterior  margin  of 
the  foramen  magnum. 

These  ligaments  serve  to  limit  the  extent  to  which  rotation  of  the  head 
may  be  carried,  hence  they  are  termed  check  ligaments. 

4.  Articulation  of  the  Atlas  with  the  Axis. — The  ligaments  of 
this  articulation  arejive  in  number — 

Anterior  atlo-axoid,  Two  capsular, 

Posterior  atlo-axoid,  Transverse. 

The  anterior  ligament  consists  of  ligamentous  fibres,  which 
pass  from  the  anterior  tubercle  and  arch  of  the  atlas  to  the 
base  of  the  odontoid  process  and  body  of  the  axis,  where  they 


538  THE   DISSECTOR. 

are  continuous  with  the  commencement  of  the  anterior  common 
ligament. 

The  posterior  ligament  is  a  thin  and  membranous  layer,  passing 
between  the  posterior  arch  of  the  atlas  and  the  laminae  of  the 
axis. 

The  capsular  ligaments  surround  the  articular  processes  of  the 
atlas  and  axis  ;  they  are  loose,  to  permit  of  the  freedom  of  move- 
ment which  subsists  between  these  vertebrae.  The  ligamentous 
fibres  are  most  numerous  on  the  outer  and  anterior  part  of  the 
articulation,  and  the  synovial  membrane  usually  communicates 
with  the  synovial  cavity  situated  between  the  transverse  ligament 
and  the  odontoid  process. 

The  transverse  ligament  is  a  strong  ligamentous  band,  which 
arches  across  the  area  of  the  ring  of  the  atlas,  from  a  rough 
tubercle  upon  the  inner  surface  of  one  articular  process  to  a  cor- 
responding tubercle  on  the  other.  It  serves  to  retain  the  odontoid 
process  of  the  axis,  in  connection  with  the  anterior  arch  of  the  atlas. 
As  it  crosses  the  odontoid  process  some  fibres  are  sent  downwards, 
to  be  attached  to  the  body  of  the  axis,  and  others  pass  upwards, 
to  be  inserted  into  the  basilar  process  of  the  occipital  bone ; 
hence  the  ligament  has  a  cross-like  appearance,  and  has  been 
denominated  cruciform.  A  synovial  membrane  is  situated  be- 
tween the  transverse  ligament  and  the  odontoid  process  ;  and 
another,  between  that  process  and  the  inner  surface  of  the  ante- 
rior arch  of  the  atlas. 

ACTIONS. — It  is  the  peculiar  disposition  of  the  transverse  ligament  in 
relation  to  the  odontoid  process,  that  enables  the  atlas,  and  with  it  the 
entire  cranium,  to  rotate  upon  the  axis  ;  the  perfect  freedom  of  move- 
ment between  these  bones  being  insured  by  the  synovial  membranes. 
The  lower  part  of  the  ring,  formed  by  the  transverse  ligament  with  the 
atlas,  is  smaller  than  the  upper,  while  the  summit  of  the  odontoid  pro- 
cess is  larger  than  its  base  ;  so  that  the  process  is  retained  in  its  position 
by  the  transverse  ligament,  when  the  other  ligaments  are  cut  through. 
The  extent  to  which  the  rotation  of  the  head  upon  the  axis  can  be  car- 
ried, is  determined  by  the  odontoid  ligaments.  The  odontoid  process 
with  its  ligaments  is  covered  in  by  the  occipito-axoid  ligament. 

5.  Articulation  of  the  Lower  Jaw. — The  lower  jaw  has  pro- 
perly but  one  ligament,  the  external  lateral ;  the  ligaments  usu- 
ally described  are  three  in  number  ;  to  which  may  be  added,  as 
appertaining  to  the  mechanism  of  the  joint,  an  interarticular 
fibrous-cartilage,  and  two  synovial  membranes,  thus  : — 
External  lateral,  Interarticular  fibrous 

Internal  lateral,  cartilage, 

Capsular,  Two  synovial  membranes. 

The  external  lateral  ligament  is  a  short  and  thick  band  of  fibres, 
passing  obliquely  backwards  from  the  tubercle  of  the  zygoma  to 
the  external  surface  of  the  neck  of  the  lower  jaw.  It  is  in  rela- 


ARTICULATION   OF   THE   JAW.  539 

tion,  externally,  with  the  integument  of  the  face,  and,  internally, 
with  the  two  synovial  membranes  of  the  articulation  and  the 
interarticular  cartilage.  The  external  lateral  ligament  acts 
conjointly  with  its  fellow  of  the  opposite  side  of  the  head,  in  the 
movements  of  the  jaw. 

The  internal  lateral  ligamenth&s  no  connection  with  the  articu- 
lation of  the  lower  jaw,  and  is  incorrectly  named  in  relation  to 
that  joint ;  it  is  a  thin  aponeurotic  expansion,  extending  from  the 
extremity  of  the  spinous  process  of  the  sphenoid  bone  to  the 
margin  of  the  dental  foramen  ;  and  is  pierced,  at  its  insertion,  by 
the  mylo-hyoidean  nerve. 

A  triangular  space  is  left  between  the  internal  lateral  ligament  and 
the  neck  of  the  jaw,  in  which  are  situated  the  internal  maxillary  artery, 
auriculo-temporal  nerve,  inferior  dental  artery  and  nerve,  and  part  of  the 
external  pterygoid  muscle ;  internally,  it  is  in  relation  with  the  internal 
pterygoid  muscle. 

The  capsular  ligament  consists  of  numerous  irregular  liga- 
mentous  fibres,  which  pass  from  the  edge  of  the  glenoid  cavity 
to  the  neck  of  the  lower  jaw,  and  surround  the  articulation  ;  on 
the  inner  side  of  the  joint,  they  form  a  pretty  strong  fasciculus. 
The  interarticular  fibrous  cartilage  is  a  thin  oval  plate, 
thicker  at  the  edges  than  in  the  centre,  and  placed  horizontally 
between  the  head  of  the  condyle  of  the  lower  jaw  and  the  gle- 
noid cavity.  It  is  connected  by  its  outer  border  with  the  exter- 
nal lateral  ligament,  and  in  front  receives  some  fibres  of  insertion 
of  the  external  pterygoid  muscle.  Occasionally,  it  is  incomplete 
in  the  centre.  It  divides  the  joint  into  two  distinct  cavities,  the 
one  being  above  and  the  other  below  the  cartilage. 

The  synovial  membranes  are  situated  the  one  above,  the  other 
below  the  fibrous  cartilage,  the  former  being  the  larger  of  the 
two.  When  the  fibrous  cartilage  is  perforate,  the  synovial  mem- 
branes communicate. 

Besides  the  lower  jaw,  there  are  several  other  joints  provided 
with  a  complete  interarticular  cartilage,  and,  consequently,  with 
two  synovial  membranes  ;  they  are — the  sterno- clavicular  articu- 
lation, the  acromio-clavicular,  and  the  articulation  of  the  ulna  with 
the  cuneiform  bone. 

The  interarticular  fibrous  cartilages  of  the  knee-joint  are  par- 
tial, and  there  is  but  one  synovial  membrane. 

The  articulations  of  the  heads  of  the  ribs  with  the  vertebrae 
have  two  synovial  membranes  separated  by  an  interarticular  liga- 
ment without  fibrous  cartilage. 

Connected  with  the  k>wer  jaw,  though  not  with  the  joint,  is 
the  stylo-maxillary  ligament,  a  process  of  the  deep  cervical  fascia 
extended  between  the  point  of  the  styloid  process  and  the  angle 
of  the  jaw.  It  is  attached  to  the  jaw  between  the  insertions  of 


540  THE   DISSECTOR. 

the  masseter  and  internal  pterygoid  muscle,  and  separates  the 
parotid  from  the  submaxillary  gland. 

ACTIONS. — The  movements  of  the  lower  jaw  are  depression,  by  which 
the  mouth  is  opened ;  elevation,  by  which  it  is  closed  ;  a  forward  and 
backward  movement ;  and  a  movement  from  side  to  side. 

In  the  movement  of  depression,  the  interarticular  cartilage  glides  for- 
ward on  the  eminentia  articularis,  carrying  with  it  the  condyle.  If  this 
movement  be  carried  too  far,  the  superior  synovial  membrane  is  rup- 
tured, and  dislocation  of  the  fibro-cartilage  with  its  condyle  into  the  zy- 
gomatic  fossa  occurs.  In  elevation  the  fibrous  cartilage  and  condyle  are 
returned  to  their  original  position.  The  forward  and  backward  move- 
ment is  a  gliding  of  the  fibro-cartilage  upon  the  glenoid  articular  surface, 
in  the  antero-posterior  direction ;  and  the  movement  from  side  to  side,  in 
the  lateral  direction. 

Dislocations. — The  dislocations  of  the  lower  jaw  are  three  :  1.  Com- 
plete ;  2.  Partial ;  and  3.  Subluxation. 

In  Complete  dislocation,  both  condyles  are  thrown  forwards  into  the 
zygomatic  fossae. 

In  Partial  dislocation,  one  condyle  is  thrown  forwards  into  the  zygo- 
matic fossa. 

In  Subluxation,  the  condyle  is  displaced  from  its  interarticular  fibro- 
cartilage. 

6.  Articulation  of  the  Ribs  with  the  Vertebra. — The  ligaments 
of  these  articulations  are  so  strong  as  to  render  dislocation  im- 
possible ;  the  neck  of  the  rib  would  break  before  displacement 
could  occur  :  they  are  divisible  into  two  groups  :  1.  Those 
connecting  the  head  of  the  rib  with  the  bodies  of  the  vertebra  ; 
and  2.  Those  connecting  the  neck  and  tubercle  of  the  ribvfiih  the 
transverse  processes.  They  are — 

1st  Group.  2d  Group. 

Anterior  costo-vertebral  or          Anterior  costo-transverse, 
stellate,  Middle  costo-transverse, 

Capsular,  Posterior  costo-transverse. 

Interarticular  ligament. 
Two  synovial  membranes. 

The  anterior  costo-vertebral  or  stellate  ligament  consists  of  three 
short  bands  of  ligamentous  fibres  that  radiate  from  the  anterior 
part  of  the  head  of  the  rib.  The  superior  band  passes  upwards, 
and  is  attached  to  the  vertebra  above  ;  the  middle  fasciculus  is 
attached  to  the  intervertebral  substance  ;  and  the  inferior,  to  the 
vertebra  below. 

In  the  first,  eleventh,  and  twelfth  ribs,  the  three  fasciculi  are 
attached  to  the  body  of  the  corresponding  vertebra. 

The  capsular  ligament  is  a  thin  layer  of  ligamentous  fibres, 
surrounding  the  joint  in  the  interval  left  by  the  anterior  liga- 
ment ;  it  is  thickest  above  and  below  the  articulation,  and  pro- 
tects the  synovial  membranes. 


ARTICULATIONS  OF   THE   RIBS.  541 

The  inter  articular  ligament  is  a  thin  band  which  passes  be- 
tween the  sharp  crest  on  the  head  of  the  rib  and  the  interverte- 
bral  substance.  It  divides  the  joint  into  two  cavities,  which  are 
each  furnished  with  a  separate  synovial  membrane.  The  first, 
eleventh,  and  twelfth  ribs  have  no  interarticular  ligament,  and 
consequently  but  one  synovial  membrane. 

The  anterior  costo-transverse  ligament  is  a  broad  band  com- 
posed of  two  fasciculi,  which  ascend  from  the  crest-like  ridge  on 
the  neck  of  the  rib,  to  the  transverse  process  immediately  above. 
This  ligament  separates  the  anterior  from  the  dorsal  branch  of 
the  intercostal  nerve. 

The  middle  costo-transverse  ligament  is  a  very  strong  inter- 
osseous  ligament,  passing  directly  between  the  posterior  surface 
of  the  neck  of  the  rib,  and  the  transverse  process  against  which 
it  rests. 

The  posterior  costo-transverse  ligament  is  a  small  but  strong 
fasciculus,  passing  obliquely  from  the  tubercle  of  the  rib  to  the 
apex  of  the  transverse  process.  The  articulation  between  the 
tubercle  of  the  rib  and  the  transverse  process,  is  provided  with 
a  small  synovial  membrane. 

There  is  no  anterior  costo-transverse  ligament  to  the  first  or 
last  rib ;  and  only  rudimentary  posterior  costo-transverse  liga- 
ments to  the  eleventh  and  twelfth  ribs. 

ACTIONS. — The  movements  permitted  by  the  articulations  of  the  ribs 
are  upwards  and  downwards,  and  slightly  forwards  a*nd  backwards;  the 
movement  increasing  in  extent  from  the  head  to  the  extremity  of  the 
rib.  The  forward  and  backward  movement  is  very  trifling  in  the  seven 
superior,  but  greater  in  the  inferior  ribs ;  the  eleventh  and  twelfth  are 
very  movable. 

7.  Articulation  of  the  Ribs  with  the  Sternum,  and  with  each 
other. — The  ligaments  of  the  costo-sternal  articulations  are — 
Anterior  costo-sternal,  Superior  costo-sternal, 

Posterior  costo-sternal,  Inferior  costo-sternal, 

Synovial  membranes. 

The  anterior  costo-sternal  ligament  is  a  thin  band  of  ligament- 
ous  fibres,  passing  in  a  radiated  direction  from  the  extremity  of 
the  costal  cartilage  to  the  anterior  surface  of  the  sternum,  and 
intermingling  its  fibres  with  those  of  the  ligament  of  the  oppo- 
site side,  and  with  the  tendinous  fibres  of  origin  of  the  pectoralis 
major  muscle. 

The  posterior  costo-sternal  ligament  is  much  smaller  than  the 
anterior ;  and  consists  of  a  thin  fasciculus  of  fibres,  situated  on 
the  posterior  surface  of  the  articulation. 

The  superior  and  inferior  costo-sternal  ligaments  are  narrow 
fasciculi,  corresponding  with  the  breadth  of  the  cartilage,  and 
46 


542  THE   DISSECTOR. 

connecting  its  superior  and  inferior  borders  with  the  side  of  the 
sternum. 

The  synovial  membrane  is  absent  in  the  articulation  of  the 
first  rib,  its  cartilage  being  usually  continuous  with  the  sternum ; 
that  of  the  second  rib  has  an  interarticular  ligament,  with  two 
synovial  membranes. 

The  sixth  and  seventh  ribs  have  several  fasciculi  of  strong  lig- 
amentous  fibres,  passing  from  the  extremity  of  their  cartilages 
to  the  anterior  surface  of  the  ensiform  cartilage,  which  latter 
they  are  intended  to  support.  They  are  named  the  costo-xyphoid 
ligaments. 

The  sixth,  seventh,  and  eighth,  and  sometimes  the  ffth  and  the 
ninth  costal  cartilages,  have  articulations  with  each  other,  and  a 
perfect  synovial  membrane  at  each  articulation.  They  are  con- 
nected by  ligamentous  fibres  which  pass  from  one  cartilage  to 
the  other,  external  and  internal  ligaments. 

The  ninth  and  tenth  are  connected  at  their  extremities  by  liga- 
mentous fibres,  but  have  no  synovial  membranes. 

ACTIONS. — The  movements  of  the  costo-sternal  articulations  are  very 
trifling ;  they  are  limited  to  a  slight  degree  of  sliding  motion.  The  first 
rib  is  the  least,  and  the  second  the  most  movable. 

8.  Articulations  of  the  Sternum. — The  pieces  of  the  sternum 
are  connected  by  means  of  a  thin  plate  of  fibro-cartilage  placed 
between  each,  and  by  an  anterior  and  posterior  ligament.     The 
fibres  of  the  anterior  sternal  ligament  are  longitudinal  in  direc- 
tion, but  so  blended  with  the  anterior  costo-sternal  ligaments, 
and  the  tendinous  fibres  of  origin  of  the  pectoral  muscles,  as 
scarcely  to  be  distinguished  as  a  distinct  ligament.  The  posterior 
sternal  ligament  is  a  broad  smooth  plane  of  longitudinal  fibres, 
placed  upon  the  posterior  surface  of  the  bone,  and  extending 
from  the  manubrium  to  the  ensiform  cartilage.     These  ligaments 
contribute  very  materially  to  the  strength  of  the  sternum,  and  to 
the  elasticity  of  the  front  of  the  chest. 

9.  Articulation  of  the  Vertebral  Column  with  the  Pelvis. — The 
last  lumbar  vertebra  is  connected  with  the  sacrum  by  the  same 
ligaments  with  which  the  various  vertebra  are  connected  to  each 
other  ;  viz  :  anterior  and  posterior  common  ligaments,  interverte- 
bral  substance,  ligainenta  subflava,  capsular  ligaments,  and  inter 
and  supra-spinous  ligaments. 

There  are,  however,  two  proper  ligaments  connecting  the  ver- 
tebral column  with  the  pelvis  ;  these  are,  the — 

Lumbo-sacral,  Lumbo-iliac. 

The  lumbo-sacral  or  sacro-vertehral  ligament  is  a  thick  trian- 
gular fasciculus  of  ligamentous  fibres,  connected,  above,  with  the 
transverse  process  of  the  last  lumbar  vertebra;  and,  below,  with 
the  posterior  part  of  the  upper  border  of  the  sacrum. 


ARTICULATIONS   OF   THE   PELVIS.  543 

The  lumbo-iliac  or  ilio-lumbar  ligament  passes  from  the  apex 
of  the  transverse  process  of  the  last  lumbar  vertebra,  to  that  part 
of  the  crest  of  the  ilium  which  surmounts  the  sacro-iliac  articula- 
tion. It  is  triangular  in  form. 

10.  Articulations  of  the  Pelvis. — The  ligaments  belonging  to 
the  articulations  of  the  pelvis  are  divisible  into  four  groups : 
(1.)  those  connecting  the  sacrum  and  ilium  ;  (2.)  those  passing 
between  the  sacrum  and  ischium  ;  (3.)  between  the  sacrum  and 
coccyx;  (4  )  between  the  two  pubic  bones. 

1st.  Between  the  sacrum  and  ilium: — 
Sacro-iliac  anterior, 
Sacro-iliac  posterior. 
2d.  Between  the  sacrum  and  ischium  : — 
Sacro-ischiatic  anterior  (short), 
Sacro-ischiatic  posterior  (long). 
3d.  Between  the  sacrum  and  coccyx : — 
Sacro-coccygean  anterior, 
Sacro-coccygean  posterior. 
4th.  Between  the  ossa  pubis : — 
Anterior  pubic, 
Posterior  pubic, 
Superior  pubic, 
Subpubic, 

Interosseous  fibro-cartilage. 

(1.)  Between  the  Sacrum  and  Ilium. — The  anterior  sacro-iliac 
liijnment  consists  of  numerous  short  ligamentous  fibres,  which 
pass  from  bone  to  bone  on  the  anterior  surface  of  the  joint. 

The  posterior  sacro-iliac  or  interosseous  ligament  is  composed 
of  numerous  strong  fasciculi  of  ligamentous  fibres,  which  pass 
horizontally  between  the  rough  surfaces  of  the  posterior  half  of 
the  sacro-iliac  articulation,  and  constitute  the  principal  bond  of 
connection  between  the  sacrum  and  the  ilium.  One  fasciculis  of 
tliis  ligament,  longer  and  larger  than  the  rest,  is  distinguished, 
from  its  direction,  by  the  name  of  the  oblique  sacro-iliac  ligament. 
It  is  attached  by  one  extremity  to  the  posterior  superior  spine 
of  the  ilium,  and  by  the  other  to  the  third  transverse  tubercle  on 
the  posterior  surface  of  the  sacrum. 

The  surfaces  of  the  two  bones  forming  the  sacro-iliac  articula- 
tion are  partly  covered  with  cartilage,  and  partly  rough  and  con- 
nected by  the  interosseous  ligament.  The  anterior  or  auricular 
half  is  coated  with  cartilage,  which  is  thicker  on  the  sacrum 
than  on  the  ilium.  The  surface  of  the  cartilage  is  irregular  and 
provided  with  a  very  delicate  synovial  membrane,  which  cannot 


544  THE   DISSECTOR. 

be  demonstrated  in  the  adult,  but  is  apparent  in  the  young  sub- 
ject, and  in  the  female  during  pregnancy. 

(2.)  Between  the  Sacrum  and  Ischium. — The  anterior  or  lesser 
sacro  ischiatic  ligament  is  thin,  and  triangular  in  form.  It  is 
attached  by  its  apex  to  the  spine  of  the  ischium,  and  by  its 
broad  extremity  to  the  side  of  the  sacrum  and  coccyx,  interlacing 
its  fibres  with  the  greater  sacro-ischiatic  ligament. 

The  anterior  sacro-ischiatic  ligament  is  in  relation,  in  front 
with  the  coccygeus  muscle,  and  behind  with  the  posterior  liga- 
ment, with  which  its  fibres  are  intermingled.  By  its  upper 
border  it  forms  part  of  the  lower  boundary  of  the  great  sacro- 
ischiatic  foramen;  and  by  the  lower,  part  of  the  lesser  sacro-ischi- 
atic foramen. 

The  posterior  or  greater  sacro-ischiatic  ligament,  considerably 
larger,  thicker,  and  more  posterior  than  the  preceding,  is  nar- 
rower in  the  middle  than  at  each  extremity.  It  is  attached,  by 
its  smaller  end,  to  the  inner  margin  of  the  tuberosity  and  ramus 
of  the  ischium,  where  it  forms  a  falciform  process,  which  pro- 
tects the  internal  pudic  artery  and  is  continuous  with  the  obtura- 
tor fascia.  By  its  larger  extremity  it  is  inserted  into  the  side 
of  the  coccyx,  sacrum,  and  posterior  inferior  spine  of  the  ilium. 

The  posterior  sacro-ischiatic  ligament  is  in  relation,  in  front, 
with  the  anterior  ligament,  and  behind  with  the  gluteus  maximus, 
to  some  of  the  fibres  of  which  it  gives  origin.  By  its  superior 
border  it  forms  part  of  the  boundary  of  the  lesser  ischiatic  fora- 
men, and  by  its  lower  border  a  part  of  the  boundary  of  the  peri- 
neum. It  is  pierced  by  the  coccygeal  branch  of  the  ischiatic 
artery.  The  two  ligaments  convert  the  sacro-ischiatic  notches 
into  foramina. 

(3.)  Between  the  Sacrum  and  Coccyx. — The  anterior  sacro- 
coccygean  ligament  is  a  thin  fasciculus  passing  from  the  anterior 
surface  of  the  sacrum  to  the  front  of  the  coccyx. 

The  posterior  sacro-coccygean  ligament  is  a  thick  ligamentous 
layer,  which  completes  the  lower  part  of  the  sacral  canal,  and 
connects  the  sacrum  with  the  coccyx  posteriorly,  extending  as 
far  as  the  apex  of  the  latter  bone. 

Between  the  two  bones  is  a  thin  disk  of  soft  fibrous  cartilage. 
In  females  there  is  frequently  a  small  synovia!  membrane.  This 
articulation  admits  of  a  certain  degree  of  movement  backwards 
during  parturition. 

The  ligaments  connecting  the  different  pieces  of  the  coccyx 
consist  of  a  few  scattered  anterior  and  posterior  fibres  and  a  thin 
disk  of  fibro-cartilage.  They  exist  only  in  the  young  subject; 
in  the  adult  the  pieces  become  ossified. 

(4.)  Between  the  Ossa  Pubis. — The  anterior  pubic  ligament 
is  composed  of  ligamentous  fibres,  which  pass  obliquely  across 


ARTICULATIONS   OP   THE   CLAVICLE.  545 

the  union  of  the  two  bones  from  side  to  side,  and  form  an  inter- 
lacement in  front  of  the  symphysis. 

The  posterior  pubic  ligament  consists  of  a  few  irregular  fibres 
uniting  the  pubic  bones  posteriorly. 

The  superior  pubic  ligament  is  a  thick  band  of  fibres  connect- 
ing the  angles  of  the  pubic  bones  superiorly,  and  filling  the  in- 
equalities upon  the  surface  of  the  bones. 

The  subpubic  ligament  is  a  thick  arch  of  fibres  connecting  the 
two  bones  inferiorly,  and  forming  the  upper  boundary  of  the 
pubic  arch. 

The  interosseous  jibro-cartilage  unites  the  two  surfaces  of  the 
pubic  bones  in  the  same  manner  as  the  intervertebral  substance 
connects  the  bodies  of  the  vertebrae.  It  resembles  the  interver- 
tebral substance  also  in  being  composed  of  oblique  fibres  disposed 
in  concentric  layers,  which  are  more  dense  towards  the  surface 
than  near  the  centre.  It  is  thick  in  front,  and  thin  behind.  A 
synovial  membrane  is  sometimes  found  in  the  posterior  half  of  the 
articulation. 

This  articulation  becomes  movable  towards  the  latter  term 
of  pregnancy,  and  admits  of  a  slight  degree  of  separation  of  its 
surfaces. 

The  obturator  ligament  or  membrane  is  not  a  ligament  of  arti- 
culation, but  simply  a  fibrous  membrane  stretched  across  the 
obturator  foramen.  It  gives  attachment  by  its  surfaces  to  the 
two  obturator  muscles,  and  leaves  a  space  in  the  upper  part  of 
the  foramen,  for  the  passage  of  the  obturator  vessels  and  nerve. 

The  numerous  vacuities  in  the  walls  of  the  pelvis,  and  their 
closure  by  ligamentous  structures,  as  in  the  case  of  the  sacro- 
ischiatic  fissures  and  obturator  foramina,  serve  to  diminish  very 
materially  the  pressure  on  the  soft  parts  during  the  passage  of 
the  head  of  the  foetus  through  the  pelvis  in  parturition. 

LIGAMENTS  OP  THE  UPPER  EXTREMITY. 

The  ligaments  of  the  upper  extremity  may  be  arranged  in  the 
order  of  the  articulations  between  the  different  bones.  They 
are  the — 

1.  Sterno-clavicular  articulation, 

2.  Scapulo-clavicular  articulation, 

3.  Ligaments  of  the  scapula, 

4.  Shoulder-joint, 

5.  Elbow-joint, 

6.  Radio-ulnar  articulation, 

7.  Wrist-joint, 

8.  Articulation  between  the  carpal  bones, 

9.  Carpo-metacarpal  articulation, 

46* 


546  THE   DISSECTOR. 

10.  Metacarpo-phalangeal  articulation, 

11.  Articulation  of  the  phalanges. 

1.  Sterno-clavicular  Articulation. — The  sterno-clavicular  is  an 
arthrodial  articulation.  Its  ligaments  are — 

Anterior  sterno-clavicular, 

Posterior  sterno-clavicular, 

Interclavicular, 

Costo-clavicular  (rhomboid), 

Interarticular  fibro-cartilage, 

Two  synovial  membranes. 

The  anterior  sterno-clavicular  ligament  is  a  broad  ligamentons 
layer  extending  obliquely  downwards  and  inwards,  covering  the 
anterior  aspect  of  the  articulation.  The  ligament  is  in  relation 
by  its  anterior  surface  with  the  integument  and  sternal  origin  of 
the  sterno-mastoid  muscle  ;  behind  with  the  interarticular  fibro- 
cartilage  and  synovial  membranes. 

The  posterior  sterno-clavicular  ligament  is  a  broad  fasciculus, 
covering  the  posterior  surface  of  the  articulation.  It  is  in  rela- 
tion by  its  anterior  surface  with  the  interarticular  fibro-cartilage 
and  synovial  membranes,  and  behind  with  the  sterno-hyoid  and 
sterno-thyroid  muscles. 

The  two  ligaments  are  continuous  at  the  upper  and  lower  part 
of  the  articulation,  so  as  to  form  a  complete  capsule  around  the 
joint. 

The  interclavicular  ligament  is  a  cord-like  band  which  crosses 
from  the  extremity  of  one  clavicle  to  that  of  the  other,  and  is 
closely  connected  with  the  upper  border  of  the  sternum.  It  is 
separated  by  cellular  tissue  from  the  sterno-thyroid  muscles. 

The  costo-clavicular  ligament  (rhomboid),  is  a  thick  fasciculus 
of  fibres,  connecting  the  sternal  extremity  of  the  clavicle  with 
the  cartilage  of  the  first  rib.  It  is  situated  obliquely  between 
the  rib  and  the  under  surface  of  the  clavicle,  and  is  in  relation 
in  front  with  the  tendon  of  origin  of  the  subclavius  muscle,  and 
behind  with  the  subclavian  vein. 

It  is  the  rupture  of  the  rhomboid  ligament  in  dislocation  of  the  ster- 
nal end  of  the  clavicle,  that  gives  rise  to  the  deformity  peculiar  to  this 
accident. 

The  interarticular  Jibro-cartilage  is  nearly  circular  in  form, 
and  thicker  at  the  edges  than  in  the  centre.  It  is  attached, 
above  to  the  clavicle,  below  to  the  cartilage  of  the  first  rib,  and 
throughout  the  rest  of  its  circumference  to  the  anterior  and  pos- 
terior sterno-clavicular  ligaments.  It  divides  the  joint  into  two 
cavities,  which  are  lined  by  distinct  synovial  membranes.  This 
cartilage  is  sometimes  pierced  through  its  centre,  and  not  unfre- 
quently  deficient,  to  a  greater  or  less  extent,  at  its  lower  part. 


ARTICULATIONS   OF  THE   CLAVICLE.  54T 

ACTIONS. — The  movements  of  the  sterno-clavicular  articulation  are,  a 
gliding  movement  of  the  fibro-cartilage  with  the  clavicle,  upon  the  articu- 
lar surface  of  the  sternum,  in  the  direction,  forwards,  backwards,  up- 
wards, and  downwards ;  and  circumduction.  This  articulation  is  the 
centre  of  the  movements  of  the  shoulder. 

Dislocations. — The  dislocations  of  the  sternal  extremity  are  two,  for- 
wards and  backwards.  The  dislocation  forwards  may  be  partial. 

The  Dislocation  forwards,  if  complete,  is  accompanied  by  the  rupture 
of  all  the  ligaments  of  the  joint. 

The  Dislocation  backivards  is  extremely  rare.  Sir  Astley  Cooper  re- 
cords only  a  single  case,  which  occurred  in  consequence  of  distortion  of 
the  spine. 

2.  Sea pulo- clavicular  Articulation. — The  ligaments  of  the  sca- 
pular end  of  the  clavicle  are  the — 

Superior  acromio-clavicular, 

Inferior  acromio-clavicular, 

Coraco-clavicular  (trapezoid  and  conoid). 

Interarticular  fibro-cartilage, 

Two  synovial  membranes. 

The  superior  acromio-clavicular  ligament  is  a  moderately  thick 
plane  of  fibres  passing  between  the  extremity  of  the  clavicle  and 
acromion,  on  the  upper  surface  of  the  joint. 

The  inferior  acromio- clavicular  ligament  is  a  thin  plane  situ- 
ated on  the  under  surface.  These  two  ligaments  are  continuous 
with  each  other  in  front  and  behind,  and  form  a  complete  capsule 
around  the  joint. 

The  coraco-clavicular  ligament  (trapezoid,  conoid),  is  a  thick 
fasciculus  of  ligamentous  fibres,  passing  obliquely  between  the 
base  of  the  coracoid  process  and  the  under  surface  of  the  clavi- 
cle, and  holding  the  end  of  the  clavicle  in  firm  connection  with 
the  scapula.  When  seen  from  before,  it  has  a  quadrilateral  form  ; 
hence  it  is  named  trapezoid:  and  examined  from  behind,  it  has  a 
triangular  form,  the  base  being  upwards ;  hence  another  name, 
conoid. 

The  interarticular  fibro-cartilage  is  often  indistinct,  from  hav- 
ing partial  connections  with  the  fibro-cartilaginous  surfaces  of 
the  two  bones  between  which  it  is  placed;  and  is  not  unfre- 
quently  absent.  When  partial,  it  occupies  the  upper  part  of 
the  articulation.  The  synovial  membranes  are  very  delicate. 
There  is,  of  course,  but  one  when  the  fibro-cartilage  is  incom- 
plete. 

ACTIONS. — The  acromio-clavicular  articulation  admits  of  two  move- 
ments ;  gliding  of  the  surfaces  upon  each  other,  and  rotation  of  the  sca- 
pula upon  the  extremity  of  the  clavicle. 

/ti.-iliH-ntions. — The  scapular  end  of  the  clavicle  can  be  dislocated  in 
one  direction  only,  viz  :  upwards.  If  the  dislocation  be  severe,  the  coraco- 
clavicular  ligament  is  completely  ruptured.  It  is  a  more  frequent  acci- 
dent than  dislocation  of  the  sternal  end  of  the  clavicle. 


548  THE   DISSECTOR. 

The  proper  ligaments  of  the  scapula  are  the — 

Coraco-acromial,  Transverse. 

The  coraco-acromial  ligament  is  a  broad  and  thick  triangular 
band,  which  forms  a  protecting  arch  over  the  shoulder-joint.  It 
is  attached,  by  its  apex,  to  the  point  of  the  acromion  process  ; 
and,  by  its  base,  to  the  external  border  of  the  coracoid  process 
its  whole  length.  This  ligament  is  in  relation,  above,  with  the 
under  surface  of  the  deltoid  muscle  ;  and  below,  with  the  tendon 
of  the  supra-spinatus  muscle,  a  bursa  mucosa  being  usually  inter- 
posed. 

The  transverse  or  coracoid  ligament  is  a  narrow  but  strong 
fasciculus,  which  crosses  the  notch  in  the  upper  border  of  the 
scapula  from  the  base  of  the  coracoid  process,  and  converts  it 
into  a  foramen.  The  supra-scapular  nerve  passes  through  this 
foramen  ;  the  artery,  over  it. 

4.   Shoulder- Joint. — The    scapulo-humeral  articulation   is  an 
enarthrosis,  or  ball-and-socket  joint ;  its  ligaments  are,  the — 
Capsular,  Coraco-humeral,  Glenoid. 

The  capsular  ligament  completely  encircles  the  articulating 
head  of  the  scapula  and  head  of  the  humerus,  and  is  attached  to 
the  neck  of  each  bone.  It  is  thick  above,  where  resistance  is 
most  required,  and  strengthened  by  the  tendons  of  the  supra- 
spinatus,  infra-spinatus,  teres  minor,  and  subscapularis  muscles ; 
below,  it  is  thin  and  loose.  The  capsule  is  incomplete  at  the 
point  of  contact  with  the  tendons,  so  that  they  obtain,  upon 
their  inner  surface,  a  covering  of  synovial  membrane. 

The  coraco-humeral  ligament  is  a  broad  band  which  descends 
obliquely  outwards,  from  the  border  of  the  coracoid  process  to 
the  greater  tuberosity  of  the  humerus,  and  serves  to  strengthen 
the  superior  and  anterior  part  of  the  capsular  ligament. 

The  glenoid  ligament  is  the  prismoid  band  of  fibro-cartilage, 
which  is  attached  around  the  margin  of  the  glenoid  cavity,  for 
the  purposes  of  protecting  its  edges  and  deepening  its  cavity. 
It  divides,  superiorly,  into  two  slips,  which  are  continuous  with 
the  long  tendon  of  the  biceps  ;  hence  the  ligament  is  fre- 
quently described  as  being  formed  by  the  splitting  of  that  tendon. 
The  cavity  of  the  articulation  is  traversed  by  the  long  tendon 
of  the  biceps,  which  is  inclosed  in  a  sheath  of  synovial  membrane 
in  its  passage  through  the  joint. 

The  synovial  membrane  of  the  shoulder-joint  is  extensive ;  it 
communicates,  anteriorly,  through  an  opening  (foramen  ovale)  in 
the  capsular  ligament  with  a  large  bursal  sac,  which  lines  the 
under  surface  of  the  tendon  of  the  subscapularis  muscle.  Supe- 
riorly, it  frequently  communicates  through  another  opening  in 
the  capsular  ligament,  with  a  bursal  sac  belonging  to  the  infra- 


ARTICULATION  OP  THE  ELBOW.  549 

spinatus  muscle;  and  it,  moreover,  forms  a  sheath  around  that 
portion  of  the  tendon  of  the  biceps,  which  is  included  within  the 
joint. 

ACTIONS. — The  shoulder  joint  is  capable  of  every  variety  of  motion, 
viz  :  of  movement  forwards  and  backwards,  of  abduction  and  adduction, 
of  circumduction  and  rotation. 

invocations. — The  dislocations  of  the  head  of  the  humerus  are/owr  in 
number : — 

1.  Downwards,  and  inwards,  into  the  axilla. 

2.  Forwards,  under  the  pectoral  muscles. 

3.  Backwards,  on  the  dorsum  of  the  scapula. 

4.  Partial,  when  the  anterior  part  of  the  capsular  ligament  is  torn 
through,  and  the  head  of  the  bone  rests  against  the  coracoid  process. 

The  muscles  immediately  surrounding  the  shoulder-joint  are,  the  sub- 
scapularis,  supra-spinatus,  infra-spinatus,  teres  minor,  long  head  of  the 
triceps,  and  deltoid  ;  the  long  tendon  of  the  biceps  is  within  the  capsular 
ligament. 

5.  Elbow-Joint. — The  elbow  is  a  ginglymoid  articulation  ;  its 
ligaments  &refour  in  number  : — 

Anterior,  Internal  lateral, 

Posterior,  External  lateral. 

The  anterior  ligament  is  a  broad  and  thin  membranous  layer, 
descending  from  the  anterior  surface  of  the  humerus,  immediately 
above  the  joint,  to  the  coronoid  process  of  the  ulna  and  orbicular 
ligament.  On  each  side,  it  is  connected  with  the  lateral  liga- 
ments. It  is  composed  of  fibres  which  pass  in  three  different 
directions  ;  vertical,  transverse,  and  oblique,  the  latter  being  ex- 
tended downwards  and  outwards  to  the  orbicular  ligament,  into 
which  they  are  attached  inferiorly.  This  ligament  is  covered  in 
by  the  brachialis  anticus  muscle. 

The  posterior  ligament  is  a  broad  and  loose  layer,  passing 
between  the  posterior  surface  of  the  humerus  and  the  anterior 
surface  of  the  base  of  the  olecranon,  and  connected  at  each  side 
with  the  lateral  ligaments.  It  is  covered  in  by  the  tendon  of 
the  triceps. 

The  internal  lateral  ligament  is  a  thick  triangular  layer,  at- 
tached above,  by  its  apex,  to  the  internal  condyle  of  the  humerus; 
and  below,  by  its  expanded  border,  to  the  margin  of  the  greater 
sigmoid  cavity  of  the  ulna,  extending  from  the  coronoid  process 
to  the  olecranon.  At  its  insertion  it  is  intermingled  with  some 
transverse  fibres.  The  internal  lateral  ligament  is  in  relation 
posteriorly  with  the  ulnar  nerve. 

The  external  lateral  ligament  is  a  strong  and  narrow  band, 
which  descends  from  the  external  condyle  of  the  humerus,  to  be 
inserted  into  the  orbicular  ligament,  and  into  the  ridge  on  the 
ulna,  with  which  the  posterior  part  of  the  latter  ligament  is  con- 


550  THE   DISSECTOE. 

nected.  This  ligament  is  closely  united  with  the  tendon  of  ori- 
gin of  the  supinator  brevis  muscle. 

The  synovial  membrane  is  extensive,  and  is  reflected  from  the 
cartilaginous  surfaces  of  the  bones  upon  the  inner  surface  of  the 
ligaments.  It  surrounds,  inferiorly,  the  head  of  the  radius, 
and  forms  an  articulating  sac  between  it  and  the  lesser  sigmoid 
notch. 

ACTIONS. — The  movements  of  the  elbow-joint  are,  flexion  and  extension, 
which  are  performed  with  remarkable  precision.  The  extent  to  which 
these  movements  are  capable  of  being  effected,  is  limited,  in  front  by  the 
coronoid  process,  and  behind  by  the  olecranon. 

Dislocations. — The  dislocations  occurring  at  this  articulation  are  Jive 
in  number : — 

1.  Radius  and  ulna,  backwards. 

2.  Radius  and  ulna,  to  either  side. 

3.  Ulna,  backwards. 

4.  Radius,  forwards. 

5.  Radius,  backwards.     This  is  a  very  rare  accident. 

In  the  two  latter  dislocations,  the  annular  ligament  of  the  head  of  the 
radius  is  ruptured. 

The  muscles  immediately  surrounding,  and  in  contact  with  the  elbow- 
joint  are,  in  front,  the  brachialis  anticus  ;  to  the  inner  side,  the  pronator 
radii  teres,  flexor  sublimis  digitorum,  and  flexor  carpi  ulnaris  ;  exter- 
nally, the  extensor  carpi  radialis  brevior,  extensor  communis  digitorum, 
extensor  carpi  ulnaris,  anconeus,  and  supinator  brevis  ;  and  behind,  the 
triceps. 

6.  The  Radio-ulnar  Articulation. — The  radius  and  ulna  are 
firmly  held  together  by  ligaments  which  are  connected  with  both 
extremities  of  the  bones,  and  with  the  shaft;  they  are,  the — 
Orbicular,  Anterior  inferior, 

Oblique,  Posterior  inferior, 

Interosseous,  Interarticular  fibro-cartilage. 

The  orbicular  ligament  (annular,  coronary),  is  a  firm  band 
several  lines  in  breadth,  which  surrounds  the  head  of  the  radius, 
and  is  attached  by  each  end  to  an  extremity  of  the  lesser  sigmoid 
cavity.  It  is  strongest  behind  where  it  receives  the  external 
lateral  ligament,  and  is  lined  on  its  inner  surface  by  a  reflection 
of  the  synovial  membrane  of  the  elbow-joint. 

The  rupture  of  this  ligament  permits  the  dislocation  of  the 
bead  of  the  radius. 

The  oblique  ligament  (called  also  ligamentum  teres,  in  contra- 
distinction to  the  interosseous  ligament),  is  a  narrow  slip  of  liga- 
mentous  fibres,  descending  obliquely  from  the  base  of  the  coronoid 
process  of  the  ulna  to  the  inner  side  of  the  radius,  a  little  below 
its  tuberosity. 

The  interosseous  ligament  is  a  broad  and  thin  plane  of  aponeu- 
rotic  fibres  passing  obliquely  downwards,  from  the  sharp  ridge 


ARTICULATION  OP  THE   WRIST.  551 

on  the  radius  to  that  on  the  ulna.  It  is  deficient  superiorly,  is 
broader  in  the  middle  than  at  each  extremity,  and  is  perforated 
at  its  lower  part  for  the  passage  of  the  anterior  interosseous  ar- 
tery. The  posterior  interosseous  artery  passes  backwards,  be- 
tween the  oblique  ligament  and  the  upper  border  of  the  interos- 
seous ligament.  This  ligament  affords  an  extensive  surface  for 
the  attachment  of  muscles. 

The  interosseous  ligament  is  in  relation,  in  front,  with  the  flexor 
profundus  digitorum,  flexor  longus  pollicis,  pronator  quadratus,  and 
anterior  interosseous  artery  and  nerve ;  behind,  with  the  supinator 
l>rc vis,  extensor  ossis  metacarpi  pollicis,  extensor  primi  iuternodii  pol- 
licis, extensor  secundi  internodii  pollicis,  extensor  indicis  ;  and  near  the 
wrist,  with  the  anterior  interosseous  artery  and  posterior  interosseous 
nerve. 

The  anterior  inferior  ligament  is  a  thin  fasciculis  of  fibres, 
passing  transversely  between  the  radius  and  ulna. 

The  posterior  inferior  ligament  is  also  thin  and  loose,  and  has 
the  same  disposition  on  the  posterior  surface  of  the  articula- 
tion. 

The  interarticular,  or  triangular  fibro-cartilage,  acts  the  part 
of  a  ligament,  between  the  lower  extremities  of  the  radius  and 
ulna.  It  is  attached,  by  its  apex,  to  a  depression  on  the  inner 
surface  of  the  styloid  process  of  the  ulna  ;  and  by  its  base,  to  the 
edge  of  the  radius.  This  fibro-cartilage  is  lined,  upon  its  upper 
surface,  by  a  synovial  membrane,  which  forms  a  duplicature  be- 
tween the  radius  and  ulna,  and  is  called  the  membrana  saccifur- 
mis.  By  its  lower  surface  it  enters  into  the  articulation  of  the 
wrist-joint. 

ACTIONS. — The  movements  taking  place  between  the  radius  and  the 
ulna  are,  the  rotation  of  the  former  upon  the  latter ;  rotation  forwards 
being  termed  pronation,  and  rotation  backwards  supination.  In  these 
movements  the  head  of  the  radius  turns  upon  its  own  axis  within  the 
orbicular  ligament  and  lesser  sigmoid  notch  of  the  ulna ;  while,  inferiorly, 
the  radius  presents  a  concavity  which  moves  upon  the  rounded  head  of 
the  ulna.  The  movements  of  the  radius  are  chiefly  limited  by  the  an- 
terior and  posterior  inferior  ligaments,  hence  these  are  not  unfrequently 
ruptured  in  great  muscular  efforts. 

1 Dislocations. — The  dislocation  of  these  two  bones  from  each  other  at 
the  upper  end,  have  been  indicated  in  the  dislocations  occurring  at  the 
elbow-joint.  They  are,  the  displacement  of  the  head  of  the  radius  for- 
wards and  backwards,  and  are  accompanied  with  rupture  of  the  annular 
ligament.  At  the  lower  end  of  the  two  bones,  the  ulna  may  be  separated 
from  the  radius  by  the  rupture  of  the  connections  of  the  interarticular 
fibro-cartilaga. 

7.  Wrist-Joint. — The  wrist  is  a  ginglymoid  articulation  ;  the 
articular  surfaces  entering  into  its  formation  being  the  radius 
and  under  surface  of  the  triangular  fibro-cartilage  above,  and  the 
rounded  surfaces  of  the  scaphoid,  semilunar,  and  cuneiform  bone 
below  ;  its  ligaments  are  four  in  number  : — 


552  THE   DISSECTOR. 

Anterior,  Internal  lateral, 

Posterior,  External  lateral. 

The  anterior  ligament  is  a  broad  and  membranous  layer, 
consisting  of  three  fasciculi,  which  pass  between  the  lower 
part  of  the  radius  and  the  scaphoid,  semilunar,  and  cuneiform 
bones. 

The  posterior  ligament,  also  thin  and  loose,  passes  between  the 
posterior  surface  of  the  radius,  and  the  posterior  surface  of  the 
semilunar  and  cuneiform  bones. 

The  internal  lateral  ligament  extends  from  the  styloid  process 
of  the  ulna  to  the  cuneiform  and  pisiform  bones. 

The  external  lateral  ligament  is  attached,  by  one  extremity,  to 
the  styloid  process  of  the  radius,  and  by  the  other,  to  the  side  of 
the  scaphoid  bone,  some  of  its  fibres  being  prolonged  to  the  tra- 
pezium. The  radial  artery  rests  on  this  ligament,  as  it  passes 
backwards  to  the  first  metacarpal  space. 

The  synovial  membrane  of  the  wrist-joint  lines  the  under  sur- 
face of  the  radius  and  interarticular  cartilage  above,  and  the 
first  row  of  bones  of  the  carpus  below. 

The  relations  of  the  wrist-joint  are,  the  flexor  and  extensor  tendons  by 
which  it  is  surrounded,  and  the  radial  and  ulnar  artery. 

ACTIONS. — The  movements  of  the  wrist-joint  are  flexion,  extension, •^ad- 
duction, abduction,  and  circumduction.  In  these  motions  the  articular 
surfaces  glide  upon  each  other. 

Dislocations. — The  dislocations  at  the  wrist-joint  are  of  three  kinds  : — 

1.  Of  both  bones,  backwards  or  forwards  ;  a  rare  accident. 

2.  Of  the  radius,  for  10 ards. 

3.  Of  the  ulna,  from  its  connection  with  the  radius. 

8.  Articulations  between  the  Carpal  Bones. — These  are  amphi- 
arthrodial  joints,  with  the  exception  of  the  conjoined  head  of  the 
os  magnum  and  unciforme,  which  is  received  into  a  cup  formed 
by  the  scaphoid,  semilunar,  and  cuneiform  bones,  and  constitutes 
an  enarthrosis.  The  ligaments  are — 

Dorsal,  Interosseous  fibro-cartilages, 

Palmar,  Anterior  annular. 

The  dorsal  ligaments  are  ligamentous  bands,  that  pass  trans- 
versely and  longitudinally  from  bone  to  bone,  upon  the  dorsal 
surface  of  the  carpus. 

The  palmar  ligaments  are  fasciculi  of  the  same  kind,  but 
stronger  than  the  dorsal,  having  the  like  disposition  on  the  pal- 
mar surface. 

The  interosseous  ligaments  are  fibro-cartilaginous  lamellae  situ- 
ated between  the  adjoining  bones  in  each  range :  in  the  upper 
range,  they  close  the  upper  part  of  the  spaces  between  the  sca- 
phoid, semilunar,  and  cuneiform  bones ;  in  the  lower  range,  they 
are  stronger  than  in  the  upper,  and  connect  the  os  magnum  on 


ARTICULATIONS   OF   THE   WRIST.  553 

the  one  side  to  the  unciforme,  on  the  other  to  the  trapezoides, 
and  leave  intervals  through  which  the  synovial  membrane  is  con- 
tinued to  the  bases  of  the  metacarpal  bones. 
*  The  anterior  annular  ligament  is  a  firm  ligamentous  band, 
which  connects  the  bones  of  the  two  sides  of  the  carpus.  It  is 
attached,  by  one  extremity,  to  the  trapezium  and  scaphoid,  and 
by  the  other,  to  the  unciform  process  of  the  unciforme  and  base 
of  the  pisiform  bone ;  it  forms  an  arch  over  the  anterior  sur- 
face of  the  carpus,  beneath  which  the  tendons  of  the  long  flexors 
and  the  median  nerve  pass  into  the  palm  of  the  hand. 

The  articulation  of  the  pisiform  bone  with  the  cuneiform  is 
provided  with  a  distinct  synovial  membrane,  which  is  protected 
by  fasciculi  of  ligamentous  fibres,  forming  a  kind  of  capsule 
around  the  joint ;  they  are  inserted  into  the  cuneiform,  unci- 
form, and  base  of  the  metacarpal  bones  of  the  little  finger. 

Synovial  Membranes. — There  are  five  synovial  membranes, 
entering  into  the  composition  of  the  articulations  of  the  carpus : 

The  first  is  situated  between  the  lower  end  of  the  ulna  and 
the  interarticular  fibro-cartilage ;  it  is  called  sacciform,  from 
forming  a  sacculus  between  the  lateral  articulation  of  the  ulna 
with  the  radius. 

The  second  is  situated  between  the  lower  surface  of  the  radius 
and  interarticular  fibro-cartilage  above,  and  the  first  range  of 
bones  of  the  carpus  below. 

The  third  is  the  most  extensive  of  the  synovial  membranes  of 
the  wrist;  it  is  situated  between  the  two  rows  of  carpal  bones, 
and  passes  between  the  bones  of  the  second  range,  to  invest 
the  carpal  extremities  of  the  four  metacarpal  bones  of  the 
fingers. 

The  fourth  is  the  synovial  membrane  of  the  articulation  of  the 
metacarpal  bone  of  the  thumb  with*  the  trapezium. 

The  fifth  is  situated  between  the  pisiform  and  cuneiform 
bones. 

ACTIONS. — Very  little  movement  exists  between  the  bones  in  each 
range,  but  more  is  permitted  between  the  two  ranges.  The  motions  in 
tin-  latter  situation  are  those  of  flexion  and  extension. 

1  > /.^locations. — The  dislocation  of  a  carpal  bone  from  violence  is  of  very 
rare  occurrence.  The  os  magnum  and  cuneiform  bones  are  sometimes  par- 
tially dislocated  from  relaxation  of  their  ligaments  ;  this  is  more  frequent 
in  the  former  than  in  the  latter  bone. 

9.  The  Carpo-metacarpal  Articulations. — The  second  row  of 
bones  of  the  carpus  articulates  with  the  metacarpal  bones  of 
the  four  fingers,  by  dorsal  and  palmar  ligaments-;  and  the  me- 
tacarpal bone  of  the  thumb  with  the  trapezium,  by  a  true  cap- 
sul-ir  I'njament.  There  is  also  in  the  carpo-metacarpal  articula- 
tion a  thin  iuterosseous  band,  which  passes  from  the  ulnar  edge 
47 


554  THE   DISSECTOR. 

of  the  os  magnum  to  the  bases  of  the  third  and  fourth  metacar- 
pal bones  at  their  point  of  connection. 

The  dorsal  ligaments  are  strong  fasciculi  which  pass  from  the 
second  range  of  carpal  to  the  metacarpal  bones  ;  with  the  ex- 
ception of  the  little  finger,  there  are  two  fasciculi  to  each  bone ; 
namely,  to  the  index  finger,  one  each  from  the  trapezium  and 
trapezoides ;  to  the  middle  finger,  one  each  from  the  trapezoides 
and  os  magnum  ;  to  the  ring  finger,  one  each  from  the  os  mag- 
num and  unciform  ;  and  to  the  little  finger,  one  from  the  unci- 
form. 

The  palmar  ligaments  are  thin  fasciculi,  arranged  upon  the 
same  plan  on  the  palmar  surface. 

The  synovial  membrane  is  a  continuation  of  the  great  synovial 
membrane  of  the  two  rows  of  carpal  bones. 

The  capsular  ligament  of  the  thumb  is  one  of  the  three  true 
capsular  ligaments  of  the  skeleton  ;  the  other  two  being  the 
shoulder-joint  and  hip-joint.  The  articulation  has  a  proper  sy- 
novial membrane. 

The  metacarpal  bones  of  the  four  fingers  are  firmly  connected 
at  their  bases  by  means  of  dorsal  and  palmar  ligaments,  which 
extend  transversely  from  one  bone  to  the  other,  and  by  interos- 
seous  ligaments,  which  pass  between  their  contiguous  surfaces. 
Their  lateral  articular  facets  are  lined  by  a  reflection  of  the  great 
synovial  membrane  of  the  two  rows  of  carpal  bones. 

ACTIONS. — The  movements  of  the  metacarpal  on  the  carpal  bones  are 
restricted  to  a  slight  degree  of  sliding  motion,  with  the  exception  of  the 
articulation  of  the  metacarpal  bone  of  the  thumb  with  the  trapezium. 
In  the  latter  articulation  the  movements  are:  flexion,  extension, adduction, 
abduction,  and  circu induction. 

Dislocations  of  these  articulations  only  occur  from  great  violence,  as 
the  bursting  of  a  gun,  or  the  crushing  of  the  hand  by  a  great  weight. 
The  kind  of  displacement  depends  therefore  upon  the  nature  of  the  in- 
jury, and  not  upon  the  peculiar  conformation  of  the  joint. 

The  metacarpal  bone  of  the  thumb  may  be  dislocated  from  the  trape- 
zium, and  thrown  inwards,  so  as  to  rest  between  the  trapezium  and  the 
base  of  the  metacarpal  bone  of  the  index  finger. 

10.  Metacarpo-phalangeal  Articulation. — The  metaearpo-pha- 
langeal  articulation  is  a  ginglymoid  joint;  its  ligaments  are  four 
in  number : — 

Anterior,  Two  lateral, 

Transverse. 

The  anterior  ligaments  are  thick  and  fibro-cartila^inous,  and 
form  part  of  the  articulating  surface  of  the  joints.  They  are 
grooved,  externally,  for  the  lodgement  of  the  flexor  tendons,  and 
by  their  internal  aspect  form  part  of  the  articular  surface  for  the 
head  of  the  metacarpal  bone.  They  are  continuous  at  each  side 
with  the  lateral  ligaments. 


ARTICULATIONS   OF  THE   PHALANGES.  555 

The  lateral  ligaments  are  strong  narrow  fasciculi,  holding  the 
bones  together  at  each  side. 

The  transverse  ligament  is  a  strong  ligamentons  band,  passing 
across  the  heads  of  the  raetacarpal  bones  of  the  four  fingers,  and 
connected  with  the  anterior  ligaments. 

The  expansion  of  the  extensor  tendon  over  the  back  of  the 
fingers  takes  the  place  of  a  posterior  ligament. 

ACTIONS. — The  articulation  admits  of  movement  in  four  different  direc- 
tions, viz :  of  flexion  extension,  adduction,  and  abduction,  the  two  latter 
being  limited  "to  a  small  extent.  It  is  also  capable  of  cir  conduction. 

Dislocations. — The  observations  upon  the  dislocations  of  the  bases  of 
the  metacarpal  bones,  relate  also  to  their  heads. 

The  first  phalanx  of  the  thumb  may  be  dislocated  backwards,  so  as  to 
rest  with  its  base  upon  the  metacarpal  bone.  This  accident  is  frequently 
rendered  compound  by  laceration  of  the  integument. 

11.  Articulation  of  the  Phalanges. — These   articulations  are 
ginglymoid  joints;  they  are  formed  by  three  ligaments. 
Anterior,  Two  lateral. 

The  anterior  ligament  is  firm  and  fibro-cartilaginous,  and  forms 
part  of  the  articular  surface  for  the  head  of  the  phalanges.  Exter- 
nally, it  is  grooved  for  the  reception  of  the  flexor  tendons. 

The  lateral  ligaments  are  very  strong;  they  are  the  principal 
bond  of  connection  between  the  bones. 

The  extensor  tendon  takes  the  place  and  performs  the  office  of 
a  posterior  ligament. 

ACTIONS. — The  movements  of  the  phalangeal  joints  are  flexion  and  ex- 
tension, these  movements  being  more  extensive  between  the  first  and 
second  phalanges  than  between  the  second  and  third. 

J Dislocations. — The  second  phalanges  are  but  rarely  dislocated  from  the 
first.  The  last  phalanges  are  dislocated  from  the  second  backwards ;  the 
base  of  the  last  phalanx  resting  upon  the  back  of  the  second  beneath  the 
extensor  tendon.  The  same  dislocation  occurs  in  the  thumb. 

In  connection  with  the  phalanges  it  may  be  proper  to  examine 
certain  fibrous  bands  termed  thecce  or  vaginal  ligaments,  which 
serve  to  retain  the  tendons  of  the  flexor  muscles  in  their  position 
u  pon  the  flat  surface  of  the  bones.  These  fibrous  bands  are  attached 
at  each  side  to  the  lateral  margins  of  the  phalanges;  they  are 
thick  in  the  interspaces  of  the  joints,  thin  where  the  tendons  lie 
upon  the  joints,  and  are  lined  upon  their  inner  surface  by  synovial 
membrane. 

LIGAMENTS  OF  THE  LOWER  EXTREMITY. 

The  ligaments  of  the  lower  extremity,  like  those  of  the  upper, 
may  be  arranged  in  the  order  of  the  joints  to  which  they  belong; 
these  are,  the — 

1.  Hip-joint. 

2.  Knee-joint. 


556  THE   DISSECTOR. 

3.  Articulation  between  the  tibia  and  fibula. 

4.  Ankle-joint. 

5.  Articulation  of  the  tarsal  bones. 

6.  Tarso-metatarsal  articulation. 

7.  Metatarso-phalangeal  articulation. 

8.  Articulation  of  the  phalanges. 

1.  Hip-Joint. — The  articulation  of  the  head  of  the  femur  with 
the  acetabulum  constitutes  an  enarthrosis,  or  ball-and-socket 
joint.  The  articular  surfaces  are  the  cup-shaped  cavity  of  the 
acetabulum  and  the  rounded  head  of  the  femur;  the  ligaments 
are  Jive  in  number,  viz : — 

Capsular,  Teres, 

Ilio-fernoral,  Cotyloid, 

Transverse. 

The  capsular  ligament  is  a  strong  ligamentous  capsule,  em- 
bracing the  acetabulum  superiorly,  and  inferiorly  the  neck  of  the 
femur,  and  connecting  the  two  bones  firmly  together.  It  is  much 
thicker  upon  the  upper  part  of  the  joint,  where  more  resistance 
is  required,  than  upon  the  under  part,  and  extends  further  upon 
the  neck  of  the  femur  on  the  anterior  and  superior  than  on  the 
posterior  and  inferior  side,  being  attached  to  the  inter-trochan- 
teric  line  in  front,  to  the  base  of  the  great  trochanter  above,  and 
to  the  middle  of  the  neck  of  the  femur  behind. 

The  ilio-femoral  ligament  is  an  accessory  and  radiating  band, 
which  descends  obliquely  from  the  anterior  inferior  spinous  pro- 
cess of  the  ilium  to  the  anterior  inter-trochanteric  line,  and 
strengthens  the  anterior  portion  of  the  capsular  ligament. 

The  ligamentum  teres,  triangular  in  shape,  is  attached,  by  a 
round  apex,  to  the  depression  just  below  the  middle  of  the  head 
of  the  femur,  and  by  its  base,  which  divides  into  two  fasciculi, 
into  the  borders  of  the  notch  of  the  acetabulum.  It  is  formed 
by  a  fasciculus  of  fibres,  of  variable  size,  surrounded  by  synovial 
membrane  ;  sometimes  the  synovial  membrane  alone  exists,  or 
the  ligament  is  wholly  absent. 

The  cotyloid  ligament  is  a  prismoid  cord  of  fibre-cartilage, 
attached  around  the  margin  of  the  acetabulum,  and  serving  to 
deepen  that  cavity  and  protect  its  edges.  It  is  much  thicker 
upon  the  upper  and  posterior  border  of  the  acetabulum  than  in 
front,  and  consists  of  fibres  which  arise  from  the  whole  circum- 
ference of  the  brim,  and  interlace  with  each  other  at  acute  angles. 
It  is  directed  inwards  towards  the  acetabulum. 

The  transverse  ligament  is  a  strong  fasciculus  of  ligamentous 
fibres,  continuous  with  the  cotyloid  ligament,  and  extended  across 
the  notch  of  the  acetabulum.  It  converts  the  notch  into  a  fora- 


ARTICULATION   OP   THE   KNEE.  557 

men,  through  which  the  articular  branches  of  the  internal  cir- 
cumflex and  obturator  arteries  enter  the  joint. 

The  fossa  at  the  bottom  of  the  acetabulum  is  filled  by  a  mass 
of  fat  covered  by  synovial  membrane,  which  serves  as  an  elastic 
cushion  for  the  head  of  the  bone  during  its  movements.  This 
was  considered  by  Havers  as  the  synovial  gland. 

The  synovial  membrane  is  extensive;  it  invests  the  head  of  the 
femur,  and  is  continued  around  the  ligamentum  teres  into  the 
acetabulum,  whence  it  is  reflected  upon  the  inner  surface  of  the 
capsular  ligament  back  to  the  head  of  the  bone. 

The  muscles  immediately  surrounding  and  in  contact  with  the  hip- 
joint  are,  in  front,  the  psoas  and  iliacus,  which  are  separated  from  the 
(  apsular  ligament  by  a  large  synovial  bursa  ;  above;  the  short  head  of 
the  rectus  and  the  gluteus  minimus;  behind,  the  pyriformis,  gemellus 
superior,  obturator  internus,  gemellus  inferior,  and  quadratus  femoris  ; 
and  to  the  inner  side,  the  obturator  externus  and  pectineus. 

ACTIONS.  —  The  movements  of  the  hip-joint  are  very  extensive  ;  they 
are  :  flexion,  extension,  adduction,  abduction,  circumduction,  and  rotation. 

Dislocations.  —  The  dislocations  of  the  hip-joint  are  four  in  number:  — 

1.  Upwards,  upon  the  dorsum  of  the  ilium. 

2.  Downwards,  into  the  foramen  ovale. 

3.  Backwards  and  upwards,  into  the  ischiatic  notch. 

4.  Forwards  and  upwards,  upon  the  body  of  the  pubes. 

2.  Knee-Joint.  —  The  knee  is  a  ginglyinoid  articulation  of  large 
size,  and  is  provided  with  numerous  ligaments;  they  are  thirteen 
in  number:  — 

Anterior  or  ligamentum  patella, 

Posterior  or  ligamentum  posticum  Winslowii, 

Internal  lateral, 

Two  external  lateral, 

Anterior  or  external  crucial, 

Posterior  or  internal  crucial, 

Transverse, 

Two  coronary. 


Two  semilunar  fibro-cartilages, 
Synovial  membrane. 

The  first  Jive  are  external  to  the  articulation  ;  the  next  five 
are  internal  to  the  articulation;  the  remaining  three  are  mere 
folds  of  synovial  membrane,  and  have  no  title  to  the  name  of 
ligaments.  In  addition  to  the  ligaments,  there  are  two  fibro- 
cartilages,  and  a  synovial  membrane. 

The  anterior  ligament,  or  ligamentum  patella,  is  the  prolonga- 
tion of  the  tendon  of  the  extensor  muscles  of  the  thigh  down- 
wards to  the  tubercle  of  the  tibia.  It  is,  therefore,  no  ligament  ; 
and,  as  the  patella  is  simply  a  sesamoid  bone  developed  in  the 

47* 


558  THE   DISSECTOR. 

tendon  of  the  extensor  muscles  for  the  defence  of  the  front  of 
the  knee-joint,  the  ligamentum  patellae  lias  no  title  to  consider- 
ation, either  as  a  ligament  of  the  knee-joint  or  as  a  ligament  of 
the  patella. 

A  small  bursa  mucosa  is  situated  between  the  ligamentum 
patellae  near  its  insertion  and  the  front  of  the  tibia,  and  another 
of  large  size  is  placed  between  the  anterior  surface  of  the  patella 
ancUthe  fascia  lata.  It  is  the  latter  which  is  inflamed  in  the 
"housemaid's  knee." 

The  posterior  ligament,  ligamentum  posticum  Winslowii,  is  a 
broad  expansion  of  ligamentous  fibres,  which  covers  the  whole 
of  the  posterior  part  of  the  joint.  It  is  divisible  into  two  lateral 
portions,  which  invest  the  condyles  of  the  femur,  and  a  central 
portion  which  is  depressed,  and  is  formed  by  the  interlacement 
of  fasciculi  passing  in  different  directions.  The  strongest  of  these 
fasciculi  is  that  which  is  derived  from  the  tendon  of  the  semi- 
membranosus ;  it  passes  obliquely  upwards  and  outwards  from 
the  posterior  part  of  the  inner  tuberosity  of  the  tibia,  to  the  ex- 
ternal condyle  of  the  femur.  Other  accessory  fasciculi  are  given 
off  by  the  tendon  of  the  popliteus  and  by  the  heads  of  the  gas- 
trocnemius.  The  middle  portion  of  the  ligament  supports  the 
popliteal  artery  and  vein,  and  is  perforated  by  several  openings 
for  the  passage  of  branches  of  the  azygos  articular  artery  and  for 
the  nerves  of  the  joint.  •  *  •'*  • 

The  internal  lateral  ligament  is  a  broad  and  trapezoid  layer  of 
ligamentous  fibres,  attached,  above,  to  the  tubercle  on  the  inter- 
nal condyle  of  the  femur;  and  below,  to  the  inner  tuberosity  of 
the  tibia.  It  is  crossed,  at  its  lower  part,  by  the  tendons  of  the 
inner  hamstring  from  which  it  is  separated  by  a  synovial  bursa, 
and  it  covers  in  the  anterior  slip  of  the  semi-membranosus  tendon 
and  the  inferior  internal  articular  artery. 

External  lateral  Ligament. — The  long  external  lateral  ligament 
is  a  strong  rounded  cord,  which  descends  from  the  posterior  part 
of  the  tubercle  upon  the  external  condyle  of  the  femur,  to  the 
outer  part  of  the  head  of  the  fibula.  The  short  external  lateral 
ligament  is  an  irregular  fasciculus  situated  behind  the  preceding, 
arising  from  the  external  condyle  near  the  origin  of  the  head  of 
the  gastrocnemius  muscle,  and  inserted  into  the  posterior  part  of 
the  head  of  the  fibula.  It  is  firmly  connected  with  the  external 
sernilunar  fibro-cartilage,  and  appears  principally  intended  to 
connect  that  cartilage  with  the  fibula.  The  long  external  lateral 
ligament  is  covered  in  by  the  tendon  of  the  biceps,  and  has  pass- 
ing beneath  it  the  tendon  of  origin  of  the  popliteus  muscle,  and 
the  inferior  external  articular  artery. 

The  true  ligaments  within  the  Joint  are,  the  crucial,  transverse, 
and  coronary. 


ARTICULATION    OF   THE   KNEE.  559 

The  anterior,  or  external  crucial  ligament,  arises  from  the  de- 
pression upon  the  head  of  the  tibia  in  front  of  the  spinous  pro- 
cess, and  passes  upwards  and  backwards,  to  be  inserted  into  the 
inner  surface  of  the- outer  condyle  of  the  femur,  as  far  as  its  pos- 
terior border.  It  is  smaller  than  the  posterior. 

The  posterior,  or  internal  crucial  ligament  arises  from  the  de- 
pression upon  the  head  of  the  tibia,  behind  the  spinous  process, 
and  passes  upwards  and  forwards,  to  be  inserted  into  the  inner 
condyle  of  the  femur.  This  ligament  is  less  oblique  and  larger 
than  the  anterior. 

The  transverse  ligament  is  a  small  slip  of  fibres,  which  extends 
transversely  from  the  external  semilunar  fibro-cartilage,  near  its 
anterior  extremity,  to  the  anterior  convexity  of  the  internal  carti- 
lage. 

The  coronary  ligaments  are  the  short  fibres  by  which  the  con- 
vex borders  of  the  semilunar  cartilages  are  connected  to  the  head 
of  the  tibia,  and  to  the  ligaments  surrounding  the  joint. 

The  semilunar  Jtbro-cartilages  are  two  falciform  plates  of  fibro- 
cartilage,  situated  upon  the  margin  of  the  head  of  the  tibia,  and 
serving  to  deepen  the  surface  of  articulation  for  the  condyles  of 
the  femur.  They  are  thick  along  their  convex  border,  and  thin 
and  sharp  along  their  concave  edge. 

The  internal  semilunar  fibro-cartilage  forms  an  oval  cup  for 
the  reception  of  the  internal  condyle  of  the  femur;  it  is  connected, 
by  its  convex  border,  to  the  head  of  the  tibia  and  to  the  internal 
and  posterior  ligaments,  by  means  of  its  coronary  ligament ;  and 
by  its  two  extremities  is  firmly  implanted  into  the  depressions  in 
front  of  and  behind  the  spinous  process.  The  external  semilunar 
fibro- cartilage  bounds  a  circular  fossa  for  the  external  condyle;  it 
is  connected  by  its  convex  border  with  the  head  of  the  tibia,  and 
to  the  external  and  posterior  ligaments  by  means  of  its  coronary 
ligament;  by  its  two  extremities  it  is  inserted  into  the  depression 
between  the  two  projections  which  constitute  the  spinous  process 
of  the  tibia.  The  two  extremities  of  the  external  cartilage  being 
inserted  into  the  same  fossa,  form  almost  a  complete  circle,  and 
the  cartilage  being  somewhat  broader  than  the  internal,  nearly 
covers  the  articular  surface  of  the  tibia.  The  external  semilunar 
fibro-cartilage,  besides  giving  off  a  fasciculus  from  its  anterior 
border  to  constitute  the  transverse  ligament,  is  continuous  by 
some  of  its  fibres  with  the  extremity  of  the  anterior  crucial  liga- 
ment; posteriorly,  it  divides  into  three  slips;  one,  a  strong  cord, 
ascends  obliquely  forwards,  and  is  inserted  into  the  anterior  part 
of  the  inner  condyle  of  the  femur  in  front  of  the  posterior  crucial 
ligament;  another  is  the  fasciculus  of  insertion  into  the  fossa  of 
the  spinous  process;  and  the  third,  of  small  size,  is  continuous 
with  the  posterior  part  of  the  anterior  crucial  ligament. 


560  THE   DISSECTOR. 

The  ligamentum  mucosum  is  a  slender  conical  process  of  syno- 
vial  membrane,  inclosing  a  few  ligamentous  fibres  which  proceed 
from  the  transverse  ligament.  It  is  connected,  by  its  apex,  with 
the  anterior  part  of  the  condyloid  notch ;  and  by  its  base,  is  lost 
in  the  mass  of  fat  which  projects  into  the  joint  beneath  the  patella. 

The  alar  ligaments  are  two  fringed  folds  of  synovial  membrane, 
extending  from  the  liganientura  mucosum,  along  the  edges  of  the 
mass  of  fat,  to  the  sides  of  the  patella. 

The  synovial  membrane  of  the  knee-joint  is  by  far  the  most 
extensive  in  the  skeleton.  It  invests  the  cartilaginous  surface  of 
the  condyles  of  the  femur,  head  of  the  tibia,  and  inner  surface  of 
the  patella.  It  covers  both  surfaces  of  the  semilunar  fibro-carti- 
lages,  and  is  reflected  upon  the  crucial  ligaments,  and  inner  sur- 
face of  the  ligaments  which  form  the  circumference  of  the  joint. 
On  each  side  of  the  patella,  it  lines  the  tendinous  aponeuroses  of 
the  vastus  internus  and  vastus  externus  muscles,  and  forms  a 
pouch  of  considerable  size  between  the  extensor  tendon  and  the 
front  of  the  femur.  It  also  forms  the  folds  in  the  interior  of  the 
joint,  called  "ligamentum  mucosum,"  and  "ligamenta  alaria." 
The  superior  pouch  of  the  synovial  membrane  is  supported  and 
raised  during  the  movements  of  the  limb  by  a  small  muscle,  the 
subcrureus,  which  is  inserted  into  it. 

Between  the  ligamentum  patellae  and  the  synovial  membrane 
is  a  considerable  mass  of  fat,  which  presses  the  membrane  to- 
wards the  interior  of  the  joint,  and  occupies  the  fossa  between 
the  two  condyles. 

Besides  the  proper  ligaments  of  the  articulation,  the  joint  is 
protected,  on  its  anterior  part,  by  the  fascia  lata,  which  is  thicker 
upon  the  outer  than  upon  the  inner  side,  by  a  tendinous  expan- 
sion from  the  vastus  internus,  and  by  some  scattered  ligamentous 
fibres  which  are  inserted  into  the  sides  of  the  patella.  The  ex- 
pansion has  been  termed  the  capsular  ligament. 

ACTIONS. — The  knee-joint  is  one  of  the  strongest  of  the  articulations  of 
the  body,  while  at  the  same  time  it  admits  of  the  most  perfect  degree  of 
movement  in  the  directions  of  flexion  and  extension.  During  flexion,  the 
articular  surface  of  the  tibia  glides  forward  on  the  condyles  of  the  femur ; 
the  lateral  ligaments,  the  posterior,  and  the  crucial  ligaments  "are  relaxed; 
while  the  ligamentum  patellae,  being  put  upon  the  stretch,  serves  to  press 
the  adipose  mass  into  the  vacuity  formed  in  the  front  of  the  joint.  In 
extension,  all  the  ligaments  are  put  upon  the  stretch,  with  the  exception 
of  the  ligamentum  patellae.  When  the  knee  is  semi-flexed,  a  partial 
degree  of  rotation  is  permitted. 

Dislocations. — The  patella  may  be  dislocated  in  three  directions  : — 

1.  Outwards,  which  is  the  most  frequent. 

2.  Inwards,  less  frequent ;  in  both  these  cases  there  will  be  rupture  of 
the  ligamentum  patellae,  unless  there  has  been  previous  weakness  of  the 

oint. 


ARTICULATION   OP   THE   TIBIA   AND   FIBULA.  561 

3.  Upwards,  accompanied  with  rupture  of  the  ligamentum  patella.  The 
dislocations  of  the  knee-joint  are/owr  in  number  : — 

1.  Tibia,  forwards. 

2.  Tibia,  'backwards. 

3.  Tibia,  to  either  side. 
The  dislocations  to  either  side  are  incomplete. 

The  semilunar  fibro-cartilages  may  become  displaced  from  relaxation  of 
the  ligaments  of  the  knee,  and  become  fitted  between  the  condyles  of  the 
femur  and  the  tibia,  so  as  to  render  the  joint  immovable. 

3.  Articulation  between  the  Tibia  and  Fibula. — The  tibia  and 
fibula  are  held  firmly  connected  by  means  of  seven  ligaments, 
viz : — 

Anterior,  ")    ,  Interosseons  inferior, 

Posterior,  j  a  Anterior,  |  ,    } 

Interosseous  membrane,  Posterior,  j 

Transverse. 

The  anterior  superior  ligament  is  a  strong  fasciculus  of  parallel 
fibres,  passing  obliquely  downwards  and  outwards,  from  the  outer 
tuberosity  of  the  tibia  to  the  anterior  surface  of  the  head  of  the 
fibula. 

The  posterior  superior  ligament,  thicker  and  stronger  than  the 
anterior,  is  disposed  in  a  similar  manner  on  the  posterior  surface 
of  the  joint. 

Within  the  articulation  there  is  a  distinct  synovial  membrane, 
which  is  sometimes  continuous  with  that  of  the  knee-joint. 

The  interosseous  membrane,  or  superior  interosseous  ligament, 
is  a  broad  layer  of  aponeurotic  fibres,  which  pass  obliquely  down- 
wards and  outwards,  from  the  sharp  ridge  on  the  tibia,  to  the 
iuner  edge  of  the  fibula,  and  are  crossed  at  an  acute  angle  by  a 
few  fibres  passing  in  the  opposite  direction.  The  ligament  is 
deficient  above,  leaving  a  considerable  interval  between  the 
bones,  through  which  the  anterior  tibial  artery  takes  its  course 
forward  to  the  anterior  aspect  of  the  leg,  and  near  its  lower 
third  there  is  an  opening  for  the  anterior  peroneal  artery  and 
vein. 

The  interosseous  membrane  is  in  relation,  in  front,  with  the 
tibialis  anticus,  extensor  longus  digitorum,  extensor  proprius 
pollicis,  anterior  tibial  vessels  and  nerve,  and  anterior  peroneal 
artery  ;  behind,  with  the  tibialis  posticus,  flexor  longus  digitorum, 
and  posterior  peroneal  artery. 

The  inferior  interosseous  ligament  consists  of  short  and  strong 
fibres,  which  hold  the  bones  firmly  together  inferiorly,  where 
they  are  nearly  in  contact.  This  articulation  is  so  firm  that 
the  fibula  is  likely  to  be  broken  in  the  attempt  to  rupture  the 
ligament. 

The  anterior  inferior  ligament  is  a  broad  band,  consisting  of 


562  THE   DISSECTOR. 

two  fasciculi  of  parallel  fibres,  which  pass  obliquely  across  the 
anterior  aspect  of  the  articulation  of  the  two  bones  at  their  infe- 
rior extremity,  from  the  tibia  to  the  fibula. 

The  posterior  inferior  ligament  is  a  similar  band,  upon  the 
posterior  surface  of  the  articulation.  Both  ligaments  project 
somewhat  below  the  margin  of  the  bones,  and  serve  to  deepen 
the  cavity  of  articulation  with  the  astragalus. 

The  transverse  ligament  is  a  narrow  band  of  ligamentous 
fibres,  continuous  with  the  preceding,  and  passing  transversely 
across  the  back  of  the  ankle-joint  between  the  two  malleoli. 

The  synovial  membrane  of  the  inferior  tibio-fibular  articulation, 
is  a  duplicature  of  the  synovial  membrane  of  the  ankle-joint,  re- 
flected upwards  for  a  short  distance  between  the  two  bones. 

ACTIONS. — Between  the  tibia  and  fibula  there  exists  an  obscure  degree 
of  movement,  which  is  principally  calculated  to  enable  the  latter  to  re- 
sist injury  by  yielding  for  a  trifling  extent  to  the  pressure  exerted. 

4.  Ankle- Joint. — The  ankle  is  a  ginglymoid  articulation  ;  the 
surfaces  entering  into  its  formation  are  the  under  surface  of  the 
tibia  with  its  malleolus  and  the  malleolus  of  the  fibula,  above  ; 
and  the  surface  of  the  astragalus  with  its  two  lateral  facets,  below. 
The  ligaments  are  three  in  number  : — 

Anterior, 
Internal  lateral,  External  lateral. 

The  anterior  ligament  is  a  thin  membranous  layer,  passing 
from  the  margin  of  the  tibia  to  the  astragalus  in  front  of  the 
articular  surface.  It  is  in  relation,  in  front,  with  the  extensor 
tendons  of  the  great  and  lesser  toes,  tendons  of  the  tibialis  anticus 
and  peroneus  tertius,  and  anterior  tibial  vessels  and  nerve.  Pos- 
teriorly, it  lies  in  contact  with  the  extra-synovial  adipose  tissue 
and  synovial  membrane. 

The  internal  lateral,  or  deltoid  ligament,  is  a  triangular  layer 
of  fibres,  attached,  superiorly,  by  its  apex  to  the  internal  mal- 
leolus, and,  inferiorly,  by  an  expanded  base  to  the  astragalus,  os 
calcis,  and  scaphoid  bone.  Beneath  the  superficial  layer  of  this 
ligament  is  a  much  stronger  and  thicker  fasciculus,  which  con- 
nects the  apex  of  the  internal  malleolus  with  the  side  of  the 
astragalus. 

This  internal  lateral  ligament  is  covered  in,  and  partly  concealed  by 
the  tendon  of  the  tibialis  posticus,  and  at  its  posterior  part,  is  in  relation 
with  the  tendons  of  the  flexor  longus  digitorum,  and  flexor  longus 
pollicis. 

The  external  lateral  ligament  consists  of  three  strong  fasciculi, 
which  proceed  from  the  inner  side  of  the  external  malleolus,  and 
diverge  in  three  different  directions.  The  anterior  fasciculus 
passes  forwards,  and  is  attached  to  the  astragalus;  the  posterior, 
backwards,  and  is  connected  with  the  astragalus  posteriorly ;  and 


ARTICULATIONS   OF  THE  TARSUS.  563 

the  middle,  longer  than  the  other  two,  descends,  to  be  inserted 
into  the  outer  side  of  the  os  calcis. 

"  It  is  the  strong  union  of  this  bone,"  says  Sir  Astley  Cooper, 
with  the  tarsal  bones,  by  means  of  the  external  lateral  ligaments, 
"  which  leads  to  its  being  more  frequently  fractured  than  dislo- 
cated." 

The  transverse  ligament  of  the  tibia  and  fibula  occupies  the 
place  of  a  posterior  ligament.  It  is  in  relation,  behind,  with  the 
posterior  tibial  vessels  and  nerve  and  tendon  of  the  tibialis  pos- 
ticus  muscle  ;  in  front,  with  the  extra-synovial  adipose  tissue  and 
synovial  membrane. 

The  synovial  membrane  invests  the  cartilaginous  surfaces  of 
the  tibia  and  fibula  (sending  a  duplicature  upwards  between 
their  lower  ends),  and  the  upper  surface  and  two  sides  of  the 
astragalus.  It  is  then  reflected  upon  the  anterior  and  lateral 
ligaments,  and  upon  the  transverse  ligament  posteriorly. 

ACTIONS. — The  movements  of  the  ankle-joint  are  flexion  and  extension 
only,  without  lateral  motion. 

Dislocations. — The  dislocations  occurring  at  this  joint,  Are  four  in  num- 
ber:— 

1.  Tibia  inwards,  the  foot  being  turned  outwards.     This  is  Pott's  dis- 
location, and  in  this  case  the  deltoid  ligament  is  ruptured,  and  the  fibula 
fractured,  at  about  three  inches  from  its  lower  extremity.     In  a  more 
severe  case,  a  portion  of  the  fibular  side  of  the  tibia  is  split  off,  and  the 
broken  end  of  the  fibula  rests  upon  the  cartilaginous  surface  of  the  astra- 
galus. 

2.  Tibia  outwards,  the  foot  being  turned  inwards.     In  this  case,  which 
is  the  most  serious  of  the  accidents  occurring  to  the  ankle-joint,  the 
inner  condyle  of  the  tibia  is  fractured,  the  deltoid  ligament  remaining 
whole;  the  fibula  is  splintered,  and  the  astragalus  sometimes  fractured. 
The  external  ligaments  generally  remain  whole ;  if  the  fibula  be  uninjured, 
they  must  be  ruptured. 

3.  Tibia  forwards.     This  is  a  partial  dislocation ;  the  tibia  is  thrown 
forwards,  so  as  to  rest  partly  on  the  scaphoid  bone ;  and  the  fibula  is 
fractured. 

4.  Both  bones  backwards.     This  is  extremely  rare ;  there  is  not  more 
than  one  or  two  cases  on  record. 

5.  Articulation  of  the  Tarsal  Bones. — The  ligaments  which 
connect  the  seven  bones  of  the  tarsus  to  each  other  are  of  three 
kinds : — 

Dorsal,  Plantar, 

Interosseous. 

The  dorsal  ligaments  are  small  fasciculi  of  parallel  fibres,  which 
pass  from  each  bone  to  all  the  neighboring  bones  with  which  it 
articulates.  The  only  dorsal  ligaments  deserving  of  particular 
mention  are,  the  external  and  posterior  calcaneo-astragaloid, 
which,  with  the  interosseous  ligament,  complete  the  articulation 
of  the  astragalus  with  the  os  calcis ;  the  superior  and  internal, 
calcanco-cuboid  ligaments  ;  and  the  superior  astragalo-scaphoid 


564  THE   DISSECTOR. 

ligament.  The  internal  calcaneo-cuboid,  and  the  superior  cal- 
caneo-scaphoid  ligament,  which  are  closely  united  posteriorly,  in 
the  deep  groove  which  intervenes  between  the  astragalus  and  os 
calcis,  separate,  anteriorly,  to  reach  their  respective  bones ;  they 
form  the  principal  bond  of  connection  between  the  first  and  se- 
cond range  of  bones  of  the  foot.  It  is  the  division  of  this  por- 
tion of  these  ligaments  that  demands  the  careful  attention  of  the 
surgeon  in  performing  Chopart's  operation. 

The  plantar  ligaments  have  the  same  disposition  on  the  plantar 
surface  of  the  foot;  three  of  them,  however,  are  of  large  size,  and 
have  especial  names,  viz  :  the — 

Calcaneo-scaphoid,  Long  calcaneo-cuboid, 

Short  calcaneo-cuboid. 

The  inferior  calcaneo-scaphoid  ligament  is  a  broad  fibro-carti- 
laginous  band  of  ligament,  which  passes  forward  from  the  an- 
terior and  inner  border  of  the  os  calcis  to  the  edge  of  the  scaphoid 
bone.  In  addition  to  connecting  the  os  calcis  and  scaphoid,  it 
supports  the  astragalus,  and  forms  part  of  the  cavity  in  which 
the  rounded  head  of  the  latter  bone  is  received.  It  is  lined  upon 
its  upper  surface  by  the  synovial  membrane  of  the  astragalo- 
scaphoid  articulation. 

The  firm  connection  of  the  os  calcis  with  the  scaphoid  bone, 
and  the  feebleness  of  the  astragalo-scaphoid  articulation,  are  con- 
ditions favorable  to  the  occasional  dislocation  of  the  head  of  the 
astragalus. 

The  long  calcaneo-cuboid,  or  ligamentum  longum  plantce,  is  a 
long  band  of  ligamentous  fibres,  which  proceeds  from  the  under 
surface  of  the  os  calcis  to  the  rough  surface  on  the  under  part  of 
the  cuboid  bone,  its  fibres  being  continued  onwards  to  the  bases 
of  the  third  and  fourth  metatarsal  bones. 

This  ligament  forms  the  inferior  boundary  of  a  canal  in  the 
cuboid  bone,  through  which  the  tendon  of  the  peroneus  longus 
passes  to  its  insertion  into  the  base  of  the  metatarsal  bone  of  the 
great  toe. 

The  short  calcaneo-cuboid  or  ligamentum  breve  plantce,  is  situ- 
ated nearer  the  bones  than  the  long  plantar  ligament,  from  which 
latter  it  is  separated  by  adipose  tissue ;  it  is  broad  and  extensive, 
and  ties  the  under  surface  of  the  os  calcis  and  cuboid  bone  firmly 
together.' 

The  interosseous  ligaments  are  five  in  number ;  they  are  short 
and  strong  ligamentous  fibres  situated  between  adjoining  bones, 
and  firmly  attach'ed  to  their  rough  surfaces.  One  of  these,  the 
calcaneo-astragaloid,  is  lodged  in  the  groove  between  the  upper 
surface  of  the  os  calcis  and  the  lower  of  the  astragalus.  It  is 
large  and  very  strong,  consists  of  vertical  and  oblique  fibres,  and 


ARTICULATIONS   OF   THE   TARSUS.  565 

serves  to  unite  the  os  calcis  and  astragalus  solidly  together.  The 
second  interosseous  ligament,  also  very  strong,  is  situated  be- 
tween the  sides  of  the  scaphoid  and  cuboid  bone  ;  while  the 
three  remaining  interosseous  ligaments  connect  strongly  together 
the  three  cuneiform  bones  and  the  cuboid. 

The  synovial  membranes  of  the  tarsus  are  four  in  number  : 
one,  for  the  posterior  calcaneo-astragaloid  articulation ;  a  second, 
for  the  anterior  calcaneo-astragaloid  and  astragalo-scaphoid  ar- 
ticulation— occasionally  an  additional  small  synovial  membrane 
is  found  in  the  anterior  calcaneo-astragaloid  joint ;  a  third,  for 
the  calcaneo-cuboid  articulation  ;  and  a  fourth,  the  large  tarsal 
synovial  membrane,  for  the  articulations  between  the  scaphoid 
and  three  cuneiform  bones,  the  cuneiform  bones  with  each  other,  the 
external  cuneiform  bone  with  the  cuboid,  and  the  two  external 
cuneiform  bones  with  the  bases  of  the  second  and  third  meta- 
tarsal  bones.  The  prolongation  which  reaches  the  metatarsal 
bones  passes  forwards  between  the  internal  and  middle  cuneiform 
bones.  A  small  synovial  membrane  is  sometimes  met  with,  be- 
tween the  contiguous  surfaces  of  the  scaphoid  and  cuboid  bone. 

ACTIONS. — The  movements  permitted  by  the  articulation  between  the 
astragalus  and  os  calcis,  are  a  slight  degree  of  gliding,  in  the  directions 
forwards  and  backwards,  and  laterally,  from  side  to  side.  The  movements 
of  the  second  range  of  tarsal  bones  are  very  trifling,  being  greater  be- 
tween the  scaphoid  and  three  cuneiform  bones  than  in  the  other  articu- 
lations. The  movements  occurring  between  the  first  and  second  range 
are  the  most  considerable  :  they  are  adduction  and  abduction,  and  in  a 
minor  degree  flexion,  which  increases  the  arch  of  the  foot,  extension,  which 
flattens  the  arch. 

1  Dislocations. — The  dislocations  of  these  bones  recorded  by  Sir  Astley 
Cooper,  are : — 

1.  Dislocation  of  the  astragalus:  in  this  case  the  calcaneo-astragaloid 
interosseous  ligament  must  be  ruptured.       1 

2.  Dislocation  of  the  live  anterior  bones  of  the  tarsus  from  the  astra- 
galus and  os  calcis. 

3.  Dislocation  of  the  internal  cuneiform  bone. 

6.  Tarso-metatarsal  Articulation. — The  ligaments  of  this  ar- 
ticulation are — 

Dorsal,  Plantar, 

Interosseous. 

The  dorsal  ligaments  connect  the  metatarsal  to  the  tarsal  bones, 
and  the  raetatarsal  bones  with  each  other.  The  precise  arrange- 
ment of  these  ligaments  is  of  little  importance ;  but  it  may  be 
remarked  that  the  base  of  the  second  metatarsal  bone,  articulat- 
ing with  the  three  cuneiform  bones,  receive*  a  ligamentous  slip 
from  each,  while  the  rest,  articulating  with  a  single  tarsal  bone, 
receive  only  a  single  tarsal  slip. 

The  plantar  ligaments  have  the  same  disposition  on  the  plantar 
surface. 
48 


566  THE   DISSECTOR. 

The  interosseous  ligaments  are  situated  between  the  bases  of 
the  metatarsal  bones  of  the  four  lesser  toes,  and  also  between 
the  bases  of  the  second  and  third  metatarsal  bones  and  the  in- 
ternal and  external  cuneiform  bones. 

The  metatarsal  bone  of  the  second  toe  is  implanted  by  its 
base  between  the  internal  and  external  cuneiform  bones,  and  is 
the  most  strongly  articulated  of  all  the  metatarsal  bones.  This 
disposition  must  be  recollected  in  amputation  at  the  tarso-meta- 
tarsal  articulation. 

The  synovial  membranes  of  this  articulation  are  three  in  num- 
ber :  one  for  the  metatarsal  bone  of  the  great  toe,  one  for  the 
second  and  third  metatarsal  bones  (which  is  continuous  with  the 
great  tarsal  synovial  membrane),  and  one  for  the  fourth  and  fifth 
metatarsal  bones. 

ACTIONS. — The  movements  of  the  metarsal  "bones  upon  the  tarsal  and 
upon  each  other,  are  very  slight ;  they  are  such  only  as  contribute  to 
the  strength  of  the  foot,  by  permitting  a  certain  degree  of  yielding  to 
opposing  forces. 

Dislocations. — These  bones  are  not  dislocated,  except  by  extreme 
violence. 

1.  Metatarso-phalangeal  Articulation. — The  ligaments  of  this 
articulation,  like  those  of  the  articulation  between  the  first  pha- 
langes and  metacarpal  bones  of  the  hand,  are  : — 

Inferior  or  plantar,  Two  lateral, 

Transverse. 

The  inferior  or  plantar  ligaments  are  thick  and  fibro-carti- 
laginous,  and  form  part  of  the  articulating  surface  of  the  joint. 

The  lateral  ligaments  are  short  and  very  strong,  and  situated 
one  on  each  side  of  the  joints. 

The  transverse  ligaments  are  strong  bands,  which  pass  trans- 
versely between  the  anterior  ligaments. 

The  expansion  of  the  extensor  tendon  supplies  the  place  of  a 
dorsal  ligament. 

ACTIONS. — The  movements  of  the  first  phalanges  upon  the  rounded 
heads  of  the  metatarsal  bones,  are :  flexion,  extension,  adduction,  and 
abduction. 

Dislocation  of  the  first  phalanges  from  the  heads  of  the  metacarpal 
bones  is  extremely  rare. 

8.  Articulation  of  the  Phalanges. — The  ligaments  of  the  pha- 
langes are  the  same  as  those  of  the  fingers,  and  have  the  same 
disposition.     Their  actions  are  also  similar.     They  are — 
Inferior  or  plantar,  Two  lateral. 


INDEX 


Abdomen,  30 

superficial  fascia  of,  .31 

arteries  of,  .'il 
Abdominal  regions,  52 
Abdominal  ring,  35 
Abductor  oculi,  130 
Acervulus,  222 
Acetabuluin,  556 
Acini,  83 

Adductor  oculi,  130 
Air-cells,  311 
Albino,  271 
Alimentary  canal,  59 
Allantois,  528 
Amphi  arthrosis,  530 
Ampulla,  281,  346 
Amygdala),  201,  223,  225 
Andersch,  ganglion  of,  190 
Aneurism,  false,  364 

varicose,  364 
Aneurismal  varix,  364 
Annulus  albidus,  266 

(.v:ilis,  316,  522 
Antihelix,  271 
Antitragus,  272 
Antrum  pylori,  59 
Anus,  64 
Aorta,  96,  325 
Aortic  sinuses,  321,  326 
Aponeurosis,  27 

Apparatus  ligamentosus  oolli,  537 
Appendices  epiploicse,  58 
Appendix  auriculae,  315,  320 

vermiformis,  62,  527 
Aqua  labyrinthi,  282 
Aquaeductus  cochleae,  282 

vestibuli,  280 
Aqueduct  of  Sylvius,  222 
Aqueous  humor,  268 
Anschnoid  membrane,  207,  246 
Arbor  vitae  cerebelli,  226 

uterina,  480 
Arch,  aortic,  326 
femoral,  412 

palmar,  superficial,  376,  378,  390 
Arciform  fibres,  232,  233 


Areola,  344 

Arnold's  ganglion,  180 

ARTERIES  : 

general  anatomy,  28 
alveolar,  174 

anastomotica  brachialis,  369 
femoralis,  409 
angular,  127,  169 
aorta,  96,  325 
articulares  genu,  427 
auricular  anterior,  171,  273 

posterior,  116,  170,  273 
axillary,  349 
azigos,  427 
basilar,  210 
brachial,  368 
bronchial,  312,  334 
buccal,  174 
bulbosi,  513 
calcanean,  444 
capsular,  98 

carotid,  common,  161,  327 
external,  166 
internal.  185,  209 
carpal  radial,  377 
ulnar,  380 
cavernosi,  513 
centralis  modioli,  281 
centralis  retinae,  138,  267,  270 
cerebellar,  211 
cerebral,  209,  211 
cervicalis  ascendens,  160 
choroidean,  210 
ciliary,  138,  270 
circumflex  femoris,  408,  425 

humeri,  351,  358,  361 
ilii,  40 

superficial,  31,  397,  406 
coccygeal,  421 
coeliac,  73,  97 
colica  dextra,  70 
sinistra,  71 
media,  70 
comes  nervi  ischiatici,  421 

phrenici,  308,  356 
ccmmunicans  cerebri,  209,  210 


568 


INDEX. 


ARTERIES — continued. 
coronaria  cordis,  322 
labii,  128 
ventriculi,  73 
corporis  bulbosi,  513 

cavernosi,  513 
cremasteric,  40,  44 
crico-thyroid,  167 
cystic,  75,  88 
deferential,  44,  462 
dental,  173,  174 
digitales  mantis,  390 

pedis,  449 

dorsales  pollicis,  378 
dorsalis  carpi,  377,  380 

hallucis,  435 

indicis,  378 

linguae,  169 

nasi,  138 

pedis,  434 

penis,  513 

pollicis,  434,  435 

scapulae,  360 
eraulgent,  98 
epigastric,  40,  100 

superficial,  31,  397,  407 
ethmoidal,  138,  256 
facial,  127  169 
femoral,  404,  405 
frontal,  116,  138 
gastric,  73 
gastro-duodenalis,  74 

epiploica  dextra,  75 
sinistra,  75 
gluteal,  420,  465 
hemorrhoidal,  superior, 72,  463,  465 

external,  512 
hepatic,  73,  81,  85 
hyoid,  167,  169 
hypogastric,  461,  521 
ileo-colic,  70 
iliac,  common,  99 
external,  99 
internal,  461 
ilio-lumbar,  463 
infra-orbital,  175 
innominata,  326 
intercostal,  39,  334,  355,  496 
anterior,  357 
superior,  161,  335 
interosseous,  379,  385 
intestini  tenuis,  70 
ischiatic,  421,  463 
labial,  128 
lachrymal,  137,  262 
laryngeal,  167 
lateralis  nasi,  128,  254 
lingual,  167 
lumbar,  39,  98 
magna  pollicis,  435 


ARTERIES — continued. 
malar,  137 
malleolar,  433 

mammary  internal,  40,  160,  356 
masseteric,  127,  174 
mastoid,  170 
maxillary,  internal,  172 

superior,  174 
mediastinal,  334,  357 
meningea,  anterior,  186,  245 
inferior,  170,  245 
media,  174,  245 
parva,  174,  245 
posterior,  210,  245 
mesenteric,  superior,  69 
inferior,  71 
metacarpal,  377,  380 
metatarsal,  435 
musculo-phrenic,  357 
mylo-hyoid,  174 
nasal,  128,  138,  175,  254 
obturator,  409,  463 
occipital,  116,  170,  496 
oesophageal,  334 
ophthalmic,  137,  186 
orbitar,  171 
ovarian,  98 
palatine,  descending,  175 

inferior,  169 

posterior,  175 

superior,  175 
palpebral,  138,  260 
pancreatica  magna,  75 
pancreaticae  parvae,  75 
pancreatico-duodenali?,  75 

inferior,  70 
parotidean,  171 
perforantes,  femoral,  408,  425 
palmares,  391 
plantares,  449 
pericardiac,  334,  357 
perinea!  superficial,  512 
peroneal,  443 
pharyngea  ascendens,  170 
phrenic,  97 
plantar,  449 
popliteal,  427 
princeps  cervicis,  496 

pollicis,  391 

profunda  cervicis,  16],  496 
femoris,  407 

humeri,  369 
pterygoid,  174 
pterygo-palatine,  175 
pubic,  40,  463 
pudic,  external,  31,  397,  407 

internal,  422,  463,  511 
pulmonary,  312 
pyloric,  75 
radial,  376,  391 


INDEX. 


569 


ART  E  RI  E  s — continued. 
rudialis  indicis,  391 
rnnine,  167,  169 
recurrens  interossese,  380 
rndinlis,  377 
tibialis,  429,  433 
ulnaris,  379 
renal,  95,  98 
sacra  lateralis,  464 

im-ilia,  99,  465 
scapular  posterior,  161,  361 
septum,  artery  of,  256 
sigmoid,  72 
spermatic,  44,  98 
spheno-palatine,  175,  256 
spinal,  210,  251 
splenic,  73,  75,  91 
sterno-mastoid,  170 
stylo-mastoid,  170 
subclavian,  157,  327 
sublingual,  169 
submaxillary,  170 
submental,  170 
subscapular,  351,  362 
superficialis  cervicis,  161 

volae,  377 

supra-orbital,  116,  137 
supra-renal,  92,  98 

scapular,  160,  360 
sural,  427 
tarsea,  435 
temporal,  116,  171 
temporales  profundaa,  174 
thoracic,  334,  350 
thyroidea  inferior,  160 
media,  326 
superior,  167         « 
tibialis  antica,  432 
postica,  442 
tonsillar,  170 
transversalis  colli,  161 

faciei,  128,  171 
humeri,  160 
perinei,  513 
tympanic,  173,  186,  278 
ulnur,  378,  390 
umbilical,  519 
uterine,  463 
vagina],  463 
vasa  brevia,  75 

intestini  tenuis,  70 
vertebral,  159,  210,  496 
vesical,  459,  462 
Vidian,  175 
Arthrodia,  531 
Articulations,  533 
Arytenoid  cartilages,  289 

glands,  296 

Auricles  of  the  heart,  315,  320.  321 
Auriculo-ventricular  openings,  316,  320 


Axilla,  348 
Axis  coeliac,  73,  97 
thyroid,  160 

Bartholine's  duct,  150 

glands,  485 
Base  of  the  brain,  226 
Bauhini,  valvula,  66 
Bichat,  fissure  of,  213 
Biliary  ducts,  84,  86,  88 
Bladder,  456,  476,  528 
Bones,  general  anatomy,  28 
Botal,  foramen  of,  526 
Brain,  204 
Brachium  anterius,  222 

posterius,  222 
Bronchi,  311,  332 
Bronchial  cells,  311 

tubes,  311,  332 
Bronchocele,  146 
Brunner's  glands,  68 
Bubonocele,  50 
Bulb,  corpus  spongiosum,  469 
Bulbi  foruicis,  229 

vestibuli,  485 

Bulbous  part  of  the  urethra,  472 
Bulbus  olfactorius,  236,  240 

rachidicus,  230 

Caecum,  62 

Calamus  scriptorius,  223 

Calices,  95 

Camper's  ligament,  510 

Canal  of  Fontana,  266 

Nuck,  483 

Petit,  268,  270 

Sylvius,  222 

Cotunnius,  280 
Canthi,  258 
Capillaries,  28 
Capitula  laryngis,  289 
Capsule  of  Glisson,  57,  76,  83 
Capsules,  supra-renal,  91,  527 
Caput  gallinaginis,  471 
Cardiac  orifice,  59 
Carpus,  552 

Cartilage,  interarticular    of    clavicle, 
546,  547 

interarticular  of  jaw,  539 

interarticular  of  wrist,  551 

semilunar,  559 
Caruncula  lachrymalis,  260 

mamillaris,  236 
Carunculae  myrtiformes,  484 
Casserian  ganglion,  176 
Cauda  equina,  248,  251 
Cava,  vena,  100,  327,  328 
Cells,  development  of,  299 
Cellular  tissue,  25 
Centrum  ovale,  212,  213 


48* 


570 


INDEX. 


Cerebellum,  224 
Cerebro-spinal  fluid,  208,  246 
Cerebrum,  212 
Ceruminous  follicles,  273 

glands,  303 
Cervical  ganglia,  194 
Chambers  of  the  eye,  268 
Cheeks,  285 

Chiasma  nervorum  opticorum,  236 
Chordae  longitudinales,  213 

tendineaa,  318,  321 

vocales,  292 

Willisii,  243 
Choroid  membrane,  265 

plexus,  215,  220,  224 
Cilia,  256,  260 
Ciliary  canal,  266 

ligament,  265.  266 

processes,  266 
Circle  of  Willis,  211 
Circulation,  adult,  315 

foetal,  519  . 
Circulus  tonsillaris,  190 

venosus  Halleri,  306 
Clitoris,  484 
Cochlea,  281 
Coeliac  axis,  73,  97 
Colon,  62 
Columna  nasi,  252 
Columnae  carneaa,  319,  321 

papil  lares,  319 
Columns  of  spinal  cord,  248 
Commissures,  221,  249 

great,  213 
Conarium,  222 
Concha,  272 

Congestion  of  the  liver,  87 
Coni  renales,  94 

vasculosi,  475 
Conjoined  tendon,  37 
Conjunctiva,  260 
Conus  arteriosus,  317 
Converging  fibres,  234 
Corium,  26,  66,  297 
Cornea,  263 
Cornicula  laryngis,  289 
Cornu  Ammonis,  217 
Cornua  of  the  ventricles,  214,  216 
Corona  glandis,  468 
Coronary  valve,  316 
Corpora  albicantia,  229 

Arantii,  319,  321 

cavernosa,  469 

geniculata,  221 

Malpighiana,  94,  95 

mammillaria,  229 

olivaria,  232 

pisiformia,  229 

pyramidalia,  231 

quadrigemina,  222 


Corpora  restiformia,  223,  232 

striata,  215 
Corpus  callosum,  213 

cavernosum,  4G9 

cilia  re,  266 

dentatum,  226,  232 

fimbriatum,  216,  217,  218 

geniculatum,  221 

Highmorianurn,  474 

luteum,  482 

psalloides,  219 

rhomboideum,  226 

spongiosum,  469 

striatum.  215 
Covered  band  of  Reil,  213 
Cowper's  glands,  516 
Cranial  nerves,  235 
Cribriform  fascia,  396,  399,  415 

lamella,  263 
Cricoid  cartilage,  289 
Circo-thyroid  membrane,  290 
Crura  cerebelli,  226 
Crura  cerebri,  230 
Crura  penis,  469 
Crural  canal,  404,  414 

ring,  405,  414 
Crystalline  lens,  269 
Cuneiform  cartilages,  290 
Cuticle,  26,  299 
Cutis,  26,  297 
Cutis  anserina,  298 
Cystic  duct,  88 
Cytoblast,  299 

Dartos,  472 
Derbyshire  neck,  146 
Derma,  26,  297 
Detrusor  urinae,  458 
Diaphragm,  105 
Diarthrosis,  531 
Digital  cavity,  216 
DISLOCATIONS  : 

ankle,  563 

carpal  bones,  553 

carpo-metacarpal,  554 

clavicle,  547 

elbow,  550 

hip,  557 

jaw,  540 

knee,  560 

metacarpo-phalangeal,  555 

metatarso-phalangeal,  566 

phalanges,  555 

radius  and  ulna,  551 

shoulder,  549 

tarsal  bones,  665 

wrist,  552 

Diverging  fibres,  233 
Dorsi-spinal  veins,  251 
Ductus  ad  nasum,  262 


INDEX. 


571 


Ductus  arteriopu?,  f>21,  f>2f> 

communis  choledochus,  76,  88 

cysticus,  88 

t  j.-ii-uhitorius,  476 

hepaticus,  84,  88 

lymphaticus  dexter,  166,  337 

pancreaticus,  90 

prostatic,  460 

thoracicus,  166,  336 

venosus,  520 
Duodenum,  60 
Dura  mater,  204,  246 

Ear,  271 

Ejaculatory  duct,  476 
Eininentia  collateral!*,  217 

pyramidal!?,  279 
Enarthrosis,  531 
Encephalon,  204 
Endocardium,  322 
Endolymph,  283 
Entozoon  folliculorum,  303 
Epiderma,  26,  299 
Epidiilymis,  473 
Epigastric  region,  52 
Epiglottic  gland,  296 
Epiglottis,  290 

Epiglotto-hyoidean  ligament,  292 
Epithelium,  66 
Erectile  tissue,  470 
Eustachian  tube,  200,  277 

valve,  316 
Eye,  268- 
Eyebrows,  258 

globe,  262 

lashes,  260 

lids,  258 

Falciform  process,  399 
Fallopian  tubes,  481 
Falx  cerebelli,  206 

cerebri,  206 
FASCIA  : 

general  anatomy  of,  26 

cervical,  141 

cremasteric,  44 

cribriform,  396,  399,  415 

deep, -27 

dentata,  218 

ili.-u-a,  108 

intercoluinnar,  35 

lata,  398 

lumbar,  491 

obturator,  454 

palmar,  386 

pelvica,  454 

perinea),  547,  505 

plantar,  446 

popliteal,  426 

propria,  43,  44,  415 


FASCIA — continued. 

recto-vesical,  454 

spermatic,  44 

superficial,  26 

temporal,  115 

transversalis,  43 
Fasciculi  graciles,  232 

innominati,  223,  232,  234 

siliquae,  232,  234 

teretes,  223,  232,  234 
Fauces,  201 
Femoral  arch,  412 

canal,  404,  414 

hernia,  412 

ring,  405,  414 
Fenestra  oval  is,  276 

rotunda,  276 

Fibraa  arciformes,  232,  233 
Fibres  of  the  brain,  233 

heart,  321 
Fibrous  cartilage  : 

interarticular  of  the 
f     clavicle,  546,  547 
jaw,  539 
knee,  559 
wrist,  551 

Filum  terminale,  247 
Fimbriac,  Fallopian,  481 
Fissura  palpebrarum,  258 
Fissure  of  Bichat,  213 

brain,  213,227 

Sylvius,  212,  228 
Fissures  of  the  liver,  79 

of  external  ear,  272 

spinal  cord,  248 
Flocculus,  225 
Foetal  circulation,  519 
Foetus,  anatomy  of,  519 
Follicles  of  Lieberkiihn,  68 
Foramen,  Botal,  of,  526 

caecum,  232,  287 

commune  anterius,  215,  218,  221 
postering,  322 

Monro,  of,  215,  218,  221 

ovale,  519,  526 

saphenum,  397 

Soemmering,  of,  268 

Window,  of,  57 
Foramina  Thebesii,  316 
Forceps  cerebri,  234 
Fornix,  216,  218 
Fossa  innominata,  272 

ischio-rectal,  505,  506 
Fossa  navicularis  urethrir,  472 

navicularis  pudendi,  483 

ovalis,  272,  316,  522 

scaphoidea,  272 

triangularis,  272 
Fourchette,  483 
Fovea  hemispherica,  279 


5T2 


INDEX. 


Fovea  elliptica,  279 

sulciformis,  279 
Frrena  epiglottidis,  287,  292 
Fraenulum  labiorum,  483 
Fraenum  labii,  285 

linguae,  287 

praeputii,  468 
Funiculi  graciles,  232 

siliquse,  232 

Galea  capitis,  114 
Gall-bladder,  87 
Ganglia,  cervical,  194 

increase  of,  233 

lumbar,  104 

sacral,  467 

semilunar,  102 

thoracic,  331 
Ganglion  of  Andersen,  190 

Arnold's,  180 

azygos,  467 

cardiac,  323 

Casserian,  176 

ciliary,  136 

Cloquet's,  183 

diaphragmaticum,  103 

geniculare,  187 

impar,  467 

jugular,  190,  191 

lenticular,  136 

Meckel's,  182 

Muller's,  190 

naso-palatine,  183 

ophthalmic,  136 

otic,  180 

petrous,  190 

semilunar,  102 

spheno-palatine,  182 

submaxillary,  180 

thyroid,  195 

vertebral,  195 

Wrisberg's,  323 
Genu  corporis  callosi,  213 
Gimbernat's  ligament,  35 
Ginglymus,  531 
Gland,  epiglottic,  296 

pineal,  222 

pituitary,  228,  241 

prostate,  460 

thymus,  523 

thyroid,  146,  523 
Glands,  aggregate,  68 

arytenoid,  296 

Bartholine's.  485 

bronchial,  337 

Brunner's,  68 

buccal,  285 

cardiac,  387 

ceruminous,  273,  303 

concatenate,  163 


Glands,  Cowpcr's,  516 

duodenal,  68 

gastric,  67 

inguinal,  32,  397 

intercostal,  337 

labial,  285 

lachrymal,  139,  261 

Lieberkuhn's,  68 

lingual,  288 

lumbar,  104 

lymphatic,  28 

mammary,  344 

mediastinal,  337 

mesenteric,  71 

Meibominn,  259 

ossophageal,  337 

Pacchionian,  205 

parotid,  122 

Peyer's,  68 

salivary,  122,  148,  149 

sebaceous,  303 

solitary,  68 

sublingual,  149 

submaxillary,  148 

sudoriferous,  303 

tracheal,  297 
Glandulae  odoriferae,  468 

Pacchioni,  205 

Tysoni,  468 
Glans  clitoridis,  484 

penis,  468 

Glisson's  capsule,  57,  76,  83 
Globus  major  epididymis,  473 

minor  epididymis,  473 
Glomeruli,  94 
Glottis,  295 
Goitre,  146 
Gomphosis,  568 
Graafian  vesicles,  482 
Gubernaculum  testis,  528 
Gums,  286 

Guthrie's  muscle,  515 
Gyri  cerebri,  212 

operti,  228 
Gyrus  fornicatus,  217 

Hair,  302 

Hamulus  lamina  spiralis,  282 

Harmonia,  530 

Heart,  313,  526 

Helicine  arteries,  470 

Helico-trema,  282 

Helix,  271 

Hepatic  duct,  84,  88 

Hernia,  congenital,  48 

diaphragmatic,  107 

direct,  49 

encysted,  49 

femoral,  412 

infantilis,  49 


INDEX. 


573 


Hernia,  inguinal,  oblique,  47 

scrotal,  50 

umbilical,  46 

ventral,  46 
Hilton's  muscle,  293 
Jlilum  lienis,  90 

pulmonis,  309 

renale,  93 
Hippocampus  major,  217 

minor,  216 

Horner's  muscle,  118  , 

Horny  band,  215 
Humors  of  the  eye,  2fi8 
Hyaloid  membrane,  269 
Hymen,  484 

Hypochondriac  regions,  52 
Hypogastric  region,  53 
Hypophysis  cerebri,  228 

Ileo-caecal  valve,  66 

Ileum,  61 

Iliac  regions,  53 

Incus,  274 

Infundibula,  95 

Infundibulum  cerebri,  228 

cordis,  317 
Inguinal  region,  53 
Integument,  26 

Interarticular    cartilages   of  the    cla- 
vicle, 546,  547 

jaw,  539 

wrist,  551 
Intercolumnar  fascia,  35 

fibres,  35 

Intermuscular  septa,  366 
Intervertebral  substance,  535 
Intestinal  canal,  60 
Intumescentia  gangliformis,  187 
Iris,  266 

Ischio-rectal  fossa,  505,  506 
Isthmus  of  the  fauces,  201 
Iter  ad  infundibulum,  221 

&  tertio  ad  quarturn  ventriculum, 
222 

Jacob's  membrane,  267 
Jejunum,  61 
Joint,  ankle,  562 

elbow.  549 

hip,  556 

lower  jaw,  538 

knee,  557 

shoulder,  548 

wrist,  551 

formation  of,  29 

Kidneys,  93,  527 

Labia  majora,  483 
minora,  483 


Labyrinth,  278 
Lachrymal  canals,  261 
gland,  139,  261 
papilla,  259 
puncta,  259,  261 
sac,  261 
tubercles,  259 
Lacteals,  71 
Lacunae,  472 
Lacus  lachrymalis,  258 
Lamina  cinerea,  227 
cribrosa,  263 
spiral!-.  282 
Laqueus,  222 
Large  intestine,  62 
Laryngotomy,  147 
Larynx,  288 
Lateral  ventricles,  214 
Lens,  269 

Lenticular  ganglion,  136 
Levers,  368,  440 
Lieberkuhn's  follicles,  68 
Lien  succenturiatus,  91 
Ligament,  29 
LIGAMENTS,  530 

acromio-clavicular,  547 
alar,  537,  560 
ankle,  of  the,  562 
annular,  of  the  ankle,  430 
radius,  550 
wrist  anterior,  533 
posterior,  373 
arena tu in  exit-run m.  105 
internum,  105 
atlo-axoid,  537 
bladder,  of  the,  454,  457 
breve  pi  an  toe,  564 
calcaneo-astragaloid,  564 
cuboid,  564 
scaphoid,  564 
capsular  of  the  hip,  556 
jaw,  539 
rib,  540 
shoulder,  548 
thumb,  554 
larynx,  290 
carpal,  552 
carpo-metacarpal,  553 
common  anterior,  534 
posterior,  534 
conoid,  547 
coracoid,  548 
coraco-acromial,  548 
clavicular,  547 
humeral,  f»ls 
coronary,  550 
coronary  of  the  knee,  559 
coeto-clavicular,  546 
coracoid,  142 
sternal,  541 


574 


INDEX. 


LIGAMENTS — continued. 
costo-transverse,  541 
vertebral,  540 
xyphoid,  542 
cotyloid,  556 
crico-arytenoid,  291 
crico-thyroidean,  290 
crucial,  559 
cruciform,  538 
deltoid,  562 
dentatum,  247 
elbow,  of  the,  549 
glenoid,  548 
glosso-epiglottic,  292 
hip-joint,  of  the,  556 
hyo-epiglottic,  292 
ilio-femoral,  556 
interarticular  of  ribs,  541 
interclavicular,  546 
interosseous : 

calcaneo-astragaloid,  564 
peroneo-tibial,  561 
radio-ulnar,  550 
inter-spinous,  536 
inter-transverse,  536 
inter-vertebral,  535 
jaw,  of  the,  538 
knee,  of  the,  557 
larynx,  of  the,  290 
lateral,  of  the  ankle,  562 

elbow,  549 

jaw,  538 

knee,  558 

phalanges,  foot,  566 

phalanges,  hand,  555 

wrist,  551 
liver,  of  the,  78 
longum  plantae,  564 
lumbo-iliac,  543 
lumbo-sacral,  542 
metacarpal,  554 
metatarsal,  566 
mucosum,  560 
nuchse,  489,  536 
oblique,  550 
obturator,  545 
occipito-atloid,  536 
axoid,  537 
odontoid,  537 
orbicular,  550 
ovary,  of  the,  482 
palpebral,  259 
patellae,  537 
pelvis,  of  the,  543 
peroneo-tibial,  561 
phalanges,  of  the  foot,  566 

of  the  hand,  555 
plantar,  long,  564 
plantar,  short,  564 
posticum  Winslowii,  424,  558 


LIGAMENTS — continued. 
Poupart's,  34 
pterygo-maxillary,  124 
pubic,  544 
pulmonis,  306 
radio-ulnar,  550 
rhomboid,  546 
rotundum,  hepatis,  78 
round,  45,  482 
sacro-coccygean,  544 
sacro-iliac,  543 
sacro-ischiatic,  544 
sacro-vertebral,  542 
scapulo-clavicular,  547 
shoulder,  of  the,  548 
stellate,  540 
sternal,  542 
sterno-clavicular,  546 
stylo-maxillary,  142,  539 
subflava,  535 
subpubic,  545 
supra-spinous,  536 
suspensoriurn  axis,  537 
hepatis,  78 
penis,  469 
tarsal,  259,  563 
tarso-metatarsal,  565 
teres,  550,  556 
thyro-arytenoid,  291 
thyro-epiglottic,  292 
thyro-hyoidean,  290 
tibio-fibular,  561 
transverse  : 

of  the  acetabulum,  556 
of  the  ankle,  563 
of  the  atlas,  538 
of  the  knee,  559 
of  the  metacarpus,  555 
of  the  metatarsus,  506 
of  the  scapula,  548 
of  the  semilunar  cartilages, 559 
trapezoid,  547 
tympanum,  of  the,  275 
uterus,  broad,  of  the,  479 
vaginal,  555 
wrist,  of  the,  551 
Zinn,  of,  130 
Ligamentum  nuchae,  489 

latum  pulmonis,  306 
Limbus  luteus,  268 
Linea  alba,  32 
Linece  semilunares,  32 

transversse,  32,  213 
Linguetta  laminosa,  223 
Lips,  285 

Liquor  Cotunnii,  282 
cornea,  264 
Morgagni,  269 
Scarpa,  of,  283 
Liver,  77,  527 


INDEX. 


575 


Lobules  of  the  liver,  80 
Lobuli  testis,  474 
Lobulus  auris,  272 

centralis  nasi,  252 

pneumogastricus,  225 
Lobus  caudatus,  81 
quadratus,  80 
Spigelii,  81 
Locus  niger,  230 

perforatus  anticus,  228 
posticus,  230 
Lumbar  fascia,  491 

regions,  53 
Lungs,  308,  526 
Lunula,  302,  319 
Lymphatic  glands  and  vessels,  28 

abdominal,  32,  104 

axillary,  349 

bronchial,  337 

cardiac,  337 

cervical,  153,  166 

iliac,  104 

inguinal,  32,  397 

intestines,  71,  73 

kidneys,  96 

lacteals,  71 

liver,  81 

lungs,  312 

mcdiastinal,  337 

mesenteric,  71 

pelvis,  465 

spleen,  91 

testicle,  473 
Lyra,  219 

Macula  cribrosa,  279 
Malleus,  274 

Malpighian  bodies,  94,  95 
Mammilla,  344 
Mammae,  344 
Mammary  gland,  344 
Mastoid  cells,  277 
Matrix,  301 

Maxillo-pharyngeal  space,  200 
Meatus  auditorius,  273 

urinarius,  female,  484 

male,  472 

Meatuses  of  the  nares,  255 
Meckel's  ganglion,  182 
Meconium,  527 
Mediastinum,  306 

testis,  474 
Medulla  innominata,  228 

oblongata,  230 
Meibomian  glands,  259 
Membrana  dentata,  247 

fusca,  265 

nictitans,  260 

pigmenti,  266 

pupillaris,  523 


Membrana  sacciform!?,  553 

tympani,  274 
Membrane,  choroid,  265 
hyaloid,  269 
Jacob's,  267 
of  the  ventricles,  224 
Membranous  urethra,  471 

labyrinth,  283 
Mesenteric  glands,  71 
Mesentery,  58 
Mesocola,  58 
Mesorectum,  58 
Metacarpus,  553 
Metatarsus,  565 
Mitral  valve,  321 
Modiolus,  281 
Mons  Veneris,  483 
Monticulus  cerebelli,  225 
Morsus  diaboli,  482 
Mouth,  284 

Mucous  membrane,  structure,  66 
MUSCLES  :" 

general  anatomy  of,  27 
abductor  indicis,  389 

minimi  digiti,  388,  447 
oculi,  130 
pollicis,  387,  447 
accelerator  urinae,  508 
accessorius,  447 
adductor  brevis,  402 
longus,  402 
magnus,  402 
minimi  digiti,  388 
oculi,  130 
pollicis,  388,  448 
anconeus,  383 
anomalus,  120 
anterior  auriculae,  115 
antitragicus,  273 
arytenoideus,  293 
aryteno-epiglottideus,  293 
attolens  aurem,  115 
oculum,  130 
atrahens  aurem,  115 
auricularis,  383 
azygos  uvulae,  202 
basio-glossus,  151 
biceps  flexor  cruris,  424 
cubiti,  366 

biventer  cervicis,  493 
brachialis  anticus,  367 
buccinator,  124 
bulbo-cavernosus,  508 
cerato-glossns,  151 
cervicalis  ascendens,  492 

•  •i  liar  is.  119 

circumflexus  palati,  202 
coccygeus,  455 
complexus,  493 
compressor  nasi,  120 


576 


INDEX. 


MUSCLES — continued. 

compressor  prostatae,  455 

urethrse,  515,  518 
constrictor  isthmi  faucium,  203 
pharyngis,  198,  199 
urethras,  515 
vaginae,  518 
coraco-brachialis,  366 
corrugator  supercilii,  118 
cremaster,  37,  528 
crico-arytenoid  lateralis,  292 
posticus,  292 
thyroideus,  292 
crureus,  401 
cucullaris,  487 
deltoid,  358 
depressor  alae  nasi,  120 

anguli  oris,  122 
epiglottidis,  293 
labii.  122 
oculi,  130 

detrusor  urinae,  458 
diaphragm,  105 
digastricus,  147 
dilatator  naris,  120 
erector  clitoridis,  484,  518 
penis,  508 
spinae,  502 

extensor  carpi  radialis,  382 
carpi  ulnaris,  382 
coccygis,  498 
digiti  minimi,  383 
digitorum  brevis,  434 
digitorum  communis,  383 
digitorum  longus,  431 
indicis,  385 

extensor  ossis  metacarpi,  384 
pollicis  proprius,  431 
internodii  pollicis,  384 
flexor  accessorius,  447 

brevis  digiti  min.,  388,  448 
carpi  radialis,  374 
ulnaris,  374 
digitorum  brevis,  447 

profundus,  375 
sublimis,  375 

longus  digitorum,  ped.,  441 
longus  pollicis,  376 
ossis  metacarpi,  387 
pollicis  brevis,  387,  448 

longus,  441 
gastrocnemius,  439 
gemellus,  419,  420 
genio-hyo-glossus,  149 

hyoideus,  149 
gluteus  maximus,  417 
medius,  418 
minimus,  418 
gracilis,  402 
helicis  major,  273 


MUSCLES — continued. 
helicis  minor,  273 
hyo-glossus,  150 
iliacus,  108,  402 
indicator,  385 
infra-spin atus,  359 
intercostales,  354 
interobliqui,  498 
interossei,  389,  434,  450 
interspinales,  498 
intertransversales,  408 
ischio-cavernosus,  508 
larynx,  of  the,  292 
latissimus  dorsi,  354,  489 
laxator  tympani,  275 
levator  anguli  oris,  ]21 

scapulae,  489 
ani,  455,  518 
glandulae  thyroidese,  146 
labii,  121,  122 
menti,  122 
palati,  202 
palpebrae,  130 
prostatae,  455 
levatores  costarum,  499 
lingualis,  151,  288 
longissimus  dorsi,  491 
longus  colli,  197 
lumbricales,  388,  447 
mallei  externus,  275 
internus,  275 
masseter,  123 
multifidus  spinae,  498 
mylo-hyoideus,  149 
myrtiformis,  120 
naso-labialis,  121 
obliquus  externus  abdominis,  34 
internus  abdominis,  35 
auris,  273 
capitis,  497 
oculi,  131 

obturator  externus,  402 
internus,  419 
occipito-frontalis,  114 
omo-hyoideus,  145 
opponens  digiti  minimi,  388 

pollicis,  387 
orbicularis  oris,  121 

palpebrarum,  118 
palato-glossus,  151,  203 
pha.ryngeus,  203 
palmaris  brevis,  386 
longus,  374 
pectineus,  402 
pectoralis  major,  346 
minor,  347 

perineus  profundus,  514 
peroneus  brevis,  437 
longus,  437 
tertius,  431 


INDEX. 


571 


MUSCLES — eontinned. 
plantaris,  439 
platysma  myoides,  141 
popliteus,  439 
posterior  auriculae,  115 
pronator  quadratus,  376 
radii  teres,  374 
psoas  magnus,  107,  402 

parvus,  108 
pterygoideus,  124 
pyramidalis  abdominis,  38 

nasi,  120 
pyriformis,  419 
quadratus  femoris,  420 

lumborum,  108 
menti,  122 

quadriceps  feraoris,  402 
rectus  abdominis,  38 

capitis  anticus  major,  197 
minor,  197 
lateralis,  497 
posticus,  497 
femoris,  401 
oculi  externus,  130 
inferior,  130 
internus,  130 
superior,  130 
retrahens  aurem,  115 
rhomboideus,  489,  490 
risorius  Santorini,  122,  141 
sacro-lumbalis,  491 
sartorius,  400 
scalenus  anticus,  157 
medius,  157 
posticus,  157 
semispinalis,  497 
semi-membranosus,  424 
semi-tendinosus,  424 
serratus  magnus,  354 
posticus,  490 
soleus,  440 

sphincter  ani,  505,  508,  518 
vagina),  518 
vesicae,  458 
ppinalis  dorsi,  492 
splenius,  491 
stapedius,  276 
sterno-hyoideus,  145 
sterno-cleido  mastoideus,  142 
thyroideus,  145 
stylo-glossus,  151 
hyoideus,  148 
pharyngeus,  200 
snbclavius,  348 
subcrureus,  402 
subscapularis,  361 
superior  auriculae,  115 
supinator  brevis,  384 
longus,  382 
supra-spinatus,  359 


MUSCLES — continued. 
temporal,  115 
tensor-palati,  202 
tensor  tarsi,  118,  261 
tympani,  275 
vaginae  iemoris,  400 
teres  major,  360 
minor,  360 

thyro-arytenoideus,  292 
epiglottideus,  293 
hyoideus,  145 
tibialis  anticus,  431 
posticus,  441 
trachelo-mastoideus,  493 
tragicus,  273 
transversalis  abdominis,  37 

colli,  492 

transversus  auriculae,  273 
pedis,  448 
perinei,  508,  518 
perinei  alter,  508 
profundus,  514,  518 
trapezius,  487 
triangularis  oris,  122 

sterni,  355 

triceps  extensor  cruris,  401 
cubiti,  367 
trochlearis,  131 
ureters,  of  the,  458 
vastus  externus,  401 
internus,  401 
Wilson's,  516 
zygomaticus,  121 
Musculi  pectinati,  316,  320 
Myopia,  271 

Naboth,  ovula  of,  480 
Nails,  361 
Nares,  252 
Nasal  duct,  262 
fossse,  254 
Nates  cerebri,  222 
NERVBS : 

general  anatomy,  28 
abducentes,  135,  238 
accessorius,  192,  240 
accessory  obturator;  412 
acromiales,  155,  357 
auditory,  283,  241 
auricularis  anterior,  118 

magnus,  118,  152 
posterior,  117,  125 
vagi,  191 

auriculo-temporal,  178 
brachial,  352 
buccal,  177 

cardiac.  192,  196,  323,  329 
carotid,  183,  190,  194 
cervical  anterior,  154 
posterior,  493 


578 


INDEX. 


NERVE  s — continued. 

cervico-facial,  125,  127 
chorda  tympani,  188,  278 
ciliary,  135,  136 
circumflex,  358,  370 
claviculares,  155 
coccygeal,  466 
cochlear,  284 
communicans  noni,  155 

peronei,  428,  439 
poplitei,  428 
tibialis,  428 
cranial,  235 
crural,  111,  410 
cutaneus  dorsi,  486 

externus  brachialis,  365, 

370 
externas  femoralis,  111, 

398 
internus  brachialis,  365,  370 

femoralis,  398 
medius  femoralis,  398 
patellae,  398,  411 
spiralis,  365,  372 
dental,  178,  182 
descendens  noni,  193 
digastric,  125 
digital,  392 
dorsal,  495 
dorsalis  penis,  514 
eighth  pair,  189,  239,  241 
facial,  125,  187,  238 
femoral,  410 
fifth  pair,  176,  241 
first  pair,  236 
fourth  pair,  238,  134 
frontal,  134 
gastric,  76,  103 
genito-crural,  111,  398 
glosso-pharyngeal,  189,  240 
gluteal,  422,  467 

inferior,  422 
gustatory,  179 
hemorrhoidal,  467,  513 
hypo-glossal.  193,  240 
ilio-hypogastric,  32,  42,  110 
ilio-inguinal,  32,  42,  110,  397 
*  incisive,  178,  179 
inferior  maxillary,  176 
infra-trochlear,  135 
inguino-cutaneous,  111,  397 
intercostal,  42,  331,  355 
intercosto-humeral,  344,  366 
interosseous  anterior,  381 

posterior,  381,  385 
ischiaticus  major,  423,  425 
minor,  422,  438 
Jacobson's,  190,  278 
labial,  179 
lachrymal,  134 


NERVE  s — continued. 

laryngeal  inferior,  192,  329 

recurrept,  192,  329 

superior,  192,  195 
lingual,  240 
lumbar  anterior,  109 

posterior,  109,  495 
lumbo-inguinal,  111 

sacral,  112 
malar,  126 
masseteric,  176 
maxillaris  inferior,  176 

superior,  176,  181 
median,  370,  380 
mental,  178 
molles,  195 

motores-oculorum,  133,  237 
musculo-cutaneous  arm,  370,  372 
leg,  430,  437 
musculo-spiral,  370,  372 
mylo-hyoidean,  179 
nasal,  135,  183,  257 
naso-ciliaris,  135 
naso-palatine,  183,  257 
ninth  pair,  193,  240,  241 
obturator,  112,  411 
occipitalis  major,  118,  493 

minor,  118,  153 
oesophageal,  329 
olfactory,  236,  256 
ophthalmic,  134,  176 
optic,  236,  267 
orbital,  181 
palatine,  183,  286 
palmar,  381,  392 
pathetici,  134,  238 
perforans  Casserii,  370 
perineal,  514 
peroneal,  428 
petrosal,  180,  183 
pharyngeal,  184,  190,  191,  195 
phrenic,  156,  307 
plantar,  449,  450 
pneumogastric,  191,  240,  328 
popliteal,  428 
portio  dura,  125,  187,  238 

mollis,  239 
pterygoid,  internal,  177 

external,  178, 

pudendalis  inferior,  423,  513 
pudendus  externus,  111 
pudic  internal,  423,  467,  513 
pulmonary,  329 
radial,  372,  380 
recurrent,  329 
renal,  103 

respiratory,  external,  157,  353 
sacral,  466 

saphenous,    external,     428,    436, 
438 


INDEX. 


519 


NERVES — cnniinnrtL 

saphenous,  long  or  internal,  398, 

405,   1 1  I 
short,  411,  428,  438 

sciatic,  422,  423,  438 

second  pair,  236 

seventh  pair,  238,  241 

sixth  pair,  238,  135,  241 

spermatic,  45,  103,  111 

spheno-palatine,  182 

spinal,  250 

spinal  accessory,  192,  240 

splanchnic,  331 

stylo-hyoid,  125 

subcutanei  colli,  127 

subcutaneous  inalae,  182 

suboccipital,  493 

subrufi,  195 

subscapnlar,  353 

superficialis  colli,  152 
cordis,  195 

superior  maxillary,  170,  181 

supra-orbital,  117,  134 

scapular,  157,  353,  360 
trochlear,  117,  134 

sympatheticus  major,  193,  329,  467 
minor,  127 

temporal,  117,  126,  177,  178 

temporo  -facial,  125 
malar,  181 

third  pair,  133,  237 

thoracic,  157,  328,  353 

thyro-hyoidean,   193 

tibialis,  anterior,  434,  436 
posterior,  444 

tonsillitic,  190 

trifacial,  176,  238 

trigeminus,  176,  238 

trochlearis,  134,  238 

tympanic,  190 

ulnar,  370,  381,  391 

vagus,  191,  240 

vestibular,  283 

Vidian,  183 

Wrisberg,  of,  365,  370 
Neurilemma,  28 
Nidus  hirundinis,  225 
Nipple,  344 
Nodulus,  223,  225 
Nodus  encephali,  230 
Nose,  252 
Nucleus  olivae,  232 
Nuck,  canal  of,  483 
Nymphae,  483 

(Esophagus,  203,  333 
Omentum,  gastro-hepatic,  57 

gastro-splenic,  59 

great,  58 

lesser,  57 


27 

Opening  in  the  diaphragm,  107 
OPERATIONS  : 

arteria  innominata,  163 

axillary  artery,  347,  350 

brachial  artery,  369 

Caesarian  section,  34 

carotid  artery,  163 

crural  hernia,  415 

dorsalis  pedis  artery,  435 

facial  artery,  169 

femoral  artery,  405 
hernia,  415 

fibular  artery,  443 

hernia,  crural,  415 
femoral,  415 
inguinal,  50 
Bcrotal,  50 

Hunter's,  405. 

inguinal  hernia,  50 

laryngotomy,  147 

lingual  artery,  168 

lithotomy,  516 

peracentesis  abdominis,  32 

peroneal  artery,  443 

plugging  nares,  257 

polypi  narium,  258 

popliteal  artery,  426 

radial  artery,  376 

Scarpa's,  405 

scrotal  hernia,  50 

subclavian  artery,  158 

tibial  artery,  anterior,  433 
posterior,  442 

tracheotomy,  147 

ulnar  artery,  379 

venesection,  363 
Optic  commissure,  228,  236 

thalami,  215,  220 
Orbiculare,  os,  274 
Orbit,  128 
Os  tincse,  479 
Ossicula  auditus,  274 
Ostium  abdominale,  481 

uterinum,  481 
Otoconites,  283 
Ovaries,  482,  528 
Oviducts,  481 
Ovisacs,  482 
Ovula  Graafiana,  482 
Naboth,  of,  480 

Pacchionian  glands,  205 
Palate,  hard,  285 

soft,  201 

Palmar  arches,  376,  378,  390 
Palpebrte,  258 
Palpebral  ligaments,  259 

sinuses,  260 
Pancreas,  89 


580 


INDEX, 


Papillae  of  the  nail,  302 

of  the  skin,  298 

of  the  tongue,  287 

calyciformes,  287 

capitatse,  288 

circumvallata3,  287 

conicae,  287 

filiformes,  287 

fungiformes,  288 

lenticulares,  287 
Parotid  gland,  122 
Peduncles  of  the  cerebellum,  226 

of  the  cerebrum,  230 

of  the  pineal  gland,  222 
Pelvis,  viscera  of,  452,  528 
Penis,  468 
Pericardium,  313 
Perilymph,  282 
Perineum,  503 
Peritoneum,  54 
Perspiratory  ducts,  304 
Pes  accessorius,  217 

anserinus,  125 

hippocampi,  217 
Peyer's  glands,  68 
Pharynx,  198 
Pia  mater,  208,  247 
Pigmentum  nigrum,  266 
Pillars  of  the  palate,  201 

of  the  external  abdominal  ring, 
Pineal  gland,  222 
Pinna,  271 
Pituitary  gland,  228,  241 

membrane,  256 
Pleura,  306 
Plexus,  aortic,  103 

axillary,  352 

brachial,  156,  352 

cardiac,  323,  324,  330 

carotid,  194 

cavernous,  194 

cervical  anterior,  155 
posterior,  495 

choroid,  215 

circulus  tonsillaris,  190 

coeliac,  102 

coronary,  323 

epigastric,  102 

gangliformis,  191 

gastric,  103 

hemorrhoidal,  465 

hepatic,  82,  103 

hypogastric,  103,  467 

lumbar,  110 

maxillary,  175,  180 

mesenteric,  103 

oasophageal,  329 

patellar,  411 

pharyngeal,  190,  192,  195 

phrenic,  103 


Plexus,  prostatic,  460,  465 

pterygoid,  175 

pulmonary,  312,  329 

renal,  103 

sacral,  466 

solar,  102 

spermatic,  45,  103 

splenic,  91,  103 

submaxillary,  152 

supra-renal,  103 

tympanic,  278 

uterine,  465 

vaginal,  465 

of  Portal  vein,  86 

vertebral,  196 

vesical,  460,  465 
Plica  semilunaris,  260 
Plicae,  longitudinales,  66 
Pneuruogastric  lobule,  225 
Polypus  of  the  heart,  315 
Pomum  Adami,  288 
Pons  Tarini,  230 
Varolii,  230 
Pores,  300 

Portal  vein,  76,  81,  84 
Portio  dura,  125,  187,  238 

mollis,  239 
Porus  optic  us,  263 
Poupart's  ligament,  34 
Prepuce,  468 
Presbyopia,  271 
Processus  e  cerebello  ad  testes,  223,  226 

brevis,  274 

clavatus,  232 

gracilis,  274 

vermiformes,  224,  225 
Promontory,  276,  277 
Prostate  gland,  460 
Prostatic  urethra,  471 
Protuberantia  annularis.  230 
Pulmonary  artery,  312,  324 

plexuses,  312,  329 

sinuses,  320 

veins,  320,  328 
Puncta  lachrymalia,  259,  261 

vasculosa,  213 
Pupil,  266 
Pylorus,  59 
Pyramid,  225,  277 
Pyramids,  anterior,  231 

Ferrein,  of,  94 

Malpighi,  of,  94 

posterior,  232 

Raphe,  corporis  callosi,  213 
Raphe  of  tongue,  287 
Receptaculum  chyli,  105,  336 
Rectum,  63,  456 
Regions,  abdominal,  52 
Reil,  island  of,  228 


INDEX. 


581 


Rete  mucosum,  26,  299 

testes,  475 
Retina,  267 
Ridley,  sinus  of,  245 
Rima  glottidis,  295 
Ring,  abdominal  external,  35 

femoral,  405,  414 

internal,  43 
Rivinian's  ducts,  150 
Root  of  lung,  309 
Rugae,  66 

Sacculus  communis,  283 

laryngis,  295 

proprius,  283 

Salivary  glands,  122,  148,  149 
Saphenous  opening,  397 

veins,  397,  425,  429 
Scala  tympani,  282 

vestibuli,  282 
Scarf-skin,  26,  299 
Scarpa's  triangle,  394 
Schindylesis,  530,  532 
Schneiderian  membrane,  256 
Sclerotic  coat,  263 
Scrotum,  472 
Sebaceous  glands,  303 
Semicircular  canals,  281 
Semilunar  fibro-cartilages,  559 

valves,  319,  321 
Septum  auricularum,  315 

crurale,  415 

lucidum,  218 

pectiniforme,  469 

scroti,  473 

Sheath  of  the  rectus,  39 
Sigmoid  flexure,  62 

valves,  319,  321 
Sinuses,  structure,  242 
Sinus  arapullaceus,  281 

aortic,  321 

basilar,  245 

cavernous,  244 

circular,  245 

fourth,  243  . 

lateral,  243 

longitudinal  inferior,  243 
superior,  242 

occipital,  243 

palpebral,  260 

petrosal  inferior,  244 
superior,  245 

pocularis,  471 

prostatic,  471 

pulmonary,  320 

rectus  or  straight,  243 

renal  is,  93 

rhomboidalis,  223 

spinal,  251 

transverse,  245 


Sinus  Valsalva,  of,  320,  321 
Skin,  297 

Small  intestines,  60 
Socia  parotid  is,  123 
Soft  palate,  201 
Spermatic  canal,  44 

cord,  44,  473 

Spheno-palatine  ganglion,  182 
Spinal  cord,  246 

nerves,  250 

veins,  251 
Spleen,  90 

Splenium  corporis  callosi,  213 
Spongy  part  of  the  urethra,  472 
Stapes,  275 
Stenon's  duct,  123 
Steatozoon  folliculorum,  303 
Stomach,  59,  527 
Striae  laterales,  213 

medullares,  239 
Structure  of  alimentary  canal,  64 

of  bladder,  458 

of  cornea,  264 

of  heart,  322 

of  liver,  82 

of  lungs,  311 

of  oesophagus,  334 

of  ovary,  482 

of  parotid  gland,  123 

of  prostate  gland,  460 

of  testicle,  474 

of  tongue,  288 

of  trachea,  332 

of  uterus,  480 

of  vagina,  478 

of  vesiculae  seminales,  461 
Sub-arachnoidean  fluid,  208,  246 

space,  207,  246 

tissue,  207 
Sublingual  gland,  149 
Submaxillary  gland,  148 
Substantia  perforate,  228 
Sudoriferous  ducts,  303 

glands,  303 
Sulci  of  the  spinal  cord,  248 
Supercilia,  258 
Superficial  fascia,  26 
Pupra-renal  capsules,  91,  527 
Suspensory  ligament,  liver,  78 

penis,  469 
Sutures,  530 

Sympathetic  system,  102,  193,  329 
Symphysis,  531 
Synarthrosis,  530 
Syndesmology,  530 
Synovia,  533 
Synovial  membrane,  533 

Tapetum  cerebri,  234 

oculi,  266 


582 


INDEX, 


Tarin,  horny  band  of,  215 

Tarsal  cartilages,  259 

Tarsus,  563 

Tela  choroidea,  219 

Tendinous  centre  of  diaphragm,  106 

Tendo  Achillis,  439 

oculi,  118 
Tendon,  27 
Tenia  hippocampi,  216,  217 

semicircular  is,  215 

Tarini,  215 

Tentorium  cerebelli,  206 
Testes  cerebri,  222 

muliebres,  482 
Testicles,  472 

descent,  529 
Thalami  optici,  215,  220 
Theca  vertebralis,  246 
Thecae,  555 

Thoracic  duct,  166,  336 
Thorax,  305 
Thymus  gland,  523 
Thyro-hyoid  membrane,  290 
Thyroid  axis,  160 
Thyroid  cartilage,  288 

gland,  146 

Tomentum  cerebri,  208 
Tongue,  286 
Tonsils,  201 

cerebelli,  225 
Torcular  Herophili,  243 
Trabs  cerebri,  213 
Trabeculae,  469 
Trachea,  296,  332 
Tracheotomy,  147 
Tractus  motorius,  237 

opticus,  236 

spiralis,  281 
Tragus,  272 

Triangles  of  the  neck,  143,  145,  148 
Triangular  ligament,  506,  510,  518 
Tricuspid  valves,  318 
Trigonum  vesicae,  459 
Trochlearis,  131,  134 
Tuber  cinereum,  228 
Tubercula  quadrigemina,  222 
Tuberculum  Loweri,  316 
Tubuli  galactophori,  345 

lactiferi,  345 

seminiferi,  474 

uriniferi,  94 

Tunica  albuginea  oculi,  26S 
testis,  474 

nervei,  65 

Ruyschiana,  266 

vaginalis,  473 

vasculosa  testis,  474 
Tutamina  oculi,  258 
Tympanum,  273 
Tyson's  glands,  468 


Umbilical  region,  53 
Urachus,  52,  457.  528 
Ureter,  95  ,    ', 

Urethra,  female,  476 

male,  470 
Uterus,  478,  528 
Utriculus  comrnunis,  283 
Uvea,  266 
Uvula  cerebelli,  223,  225 

palati,  201 

vesicae,  459 

Vagina,  478 

Vallecula,  225 

Valsalva,  sinuses  of,  320,  321 

Valve,  arachnoid,  224 

Bauhini,  66 

coronary,  316 

Eustachian,  316 

ileo-caecal,  66 

mitral,  321 

pyloric,  66 

rectum,  of  the.  66 

semilunar,  319,  321 

Tarin,  of,  225 

tricuspid,  318 

Vieussens,  of,  223,  225 
Valvulae  conniventes,  66 
Vasa  efferentia,  475 

lactea,  71,  345 

lymphatica,  28 

recta,  475 

Vasculum  aberrans,  476 
Vas  deferens,  45,  476 
VEINS  : 

structure,  28 

angular,  128 

auricular,  117,  175 

axillary,  352 

azygos,  335 

basilic,  365 

cardiac,  322 

cava  inferior,  100,  328 
superior,  327 

cephalic,  304 

cerebellar,  212 

cerebral,  211 

coronary,  315,  323 

corporis  striati,  215 

dorsalis  penis,  513 

dorsi-spinal,  251 

emulgent,  101 

facial,  128,  176 

femoral,  409 

frontal,  116 

Galeni,  212 

gastric,  76 

hepatic,  81,  85 

iliac,  101,  465 

innominatse,  327 


INDEX. 


583 


VE  I N  s — rontin  urd. 

intercostal  superior,  335 
jugular,  anterior,  153 

external,  153,  178 
internal,  164,  186 
lumbar,  101 
maxillary  internal,  175 
median,  362,  372 

basilic,  363 

cephalic,  363 
medulli-spinal,  251 
meningo-rachidian,  251 
mesenteric,  superior,  71 
inferior,  73 
occipital,  116 
ophthalmic,  139 
ovarian,  101 
parietal,  243 
phrenic,  101 
popliteal,  426 
portal,  76,  84 
profunda  femoris,  409 
prostatic,  460,  465 
pulmonary,  328 
radial,  364,  371 
renal,  96,  101 
salvatella,  371 

saphenous  external,  425,  436,  438 
internal,  397,  429,  436 
spermatic,  44,  101 
spinal,  251 
splenic,  76 
subclavian,  161 
temporal,  117,  175 
temporo-maxillary,  175 
Thebesii,  323 
thyroid,  166,  187 
tibial,  444 
ulnar,  365,  371,  372 


VEIN  s — rontimifd. 

umbilical,  519 

uterine,  465 

vertebral,  251 

vesical,  465 
Velum  interpositum,  208,  219 

medullare,  223,  225 

pendulum  palati,  201 
Venae  comites,  342 

Galeni,  215,  219 

vorticosae,  265 
Ventricles  of  the  brain  : 

fifth,  218 

fourth,  223 

lateral,  214 

third,  221 

of  the  corpus  callosnm,  213 
Ventricles  of  the  heart,  316,  320 

of  the  larynx,  295 
Vermiform  processes,  224,  225 
Vermis,  225 

Vertebral  aponeurosis,  490 
Veru  montanum,  471 
Vesiculae  seminales,  460 
Vestibule,  278 
Vestibulum  vaginae,  484 
Vibrissae,  252,  254 
Villi,  67 

Vitreous  humor,  269 
Vulva,  483 

Wharton's  duct,  148,  287 
Willis,  circle  of,  211 
Wilson's  muscles,  516 
Wrisberg,  nerve  of,  349,  365,  370 

Zonula  ciliaris,  267 
Zonula  ossea  lamina  spiralis,  282 
of  Zinn,  268 


THE  END. 


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